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Behavioral and Brain Sciences
cambridge.org/bbs
Target Article
Cite this article: Benenson JF, Webb CE,
Wrangham RW. (2022) Self-protection as an
adaptive female strategy. Behavioral and Brain
Sciences 45, e128: 1–65. doi:10.1017/
S0140525X21002417
Target Article Accepted: 1 November 2021
Target Article Manuscript Online: 8 November
2021
Commentaries Accepted: 11 February 2022
Keywords:
emotions; immunity and illness; insomnia;
longevity and survival; neuroticism; pain and
injury; reproductive success; sex differences;
social interactions; stress and threat
What is Open Peer Commentary? What
follows on these pages is known as a
Treatment, in which a significant and
controversial Target Article is published
along with Commentaries (p. 26) and an
Author’s Response (p. 59). See bbsonline.
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© The Author(s), 2021. Published by
Cambridge University Press
Self-protection as an adaptive female strategy
Joyce F. Benenson , Christine E. Webb and Richard W. Wrangham
Department of Human Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
Joyce.Benenson@gmail.com
christinewebb@fas.harvard.edu
wrangham@fas.harvard.edu
Abstract
Many male traits are well explained by sexual selection theory as adaptations to mating com-
petition and mate choice, whereas no unifying theory explains traits expressed more in
females. Anne Campbell’s“staying alive”theory proposed that human females produce
stronger self-protective reactions than males to aggressive threats because self-protection
tends to have higher fitness value for females than males. We examined whether
Campbell’s theory has more general applicability by considering whether human females
respond with greater self-protectiveness than males to other threats beyond aggression. We
searched the literature for physiological, behavioral, and emotional responses to major phys-
ical and social threats, and found consistent support for females’responding with greater
self-protectiveness than males. Females mount stronger immune responses to many patho-
gens; experience a lower threshold to detect, and lesser tolerance of, pain; awaken more fre-
quently at night; express greater concern about physically dangerous stimuli; exert more
effort to avoid social conflicts; exhibit a personality style more focused on life’s dangers;
react to threats with greater fear, disgust, and sadness; and develop more threat-based clinical
conditions than males. Our findings suggest that in relation to threat, human females have
relatively heightened protective reactions compared to males. The pervasiveness of this result
across multiple domains suggests that general mechanisms might exist underlying females’
unique adaptations. An understanding of such processes would enhance knowledge of female
health and well-being.
1. Introduction
Across diverse, contemporary human societies, numerous sex differences appear in physiology,
behavior, and experiences that often vary in magnitude depending on the culture (Archer,
2019; Berenbaum & Beltz, 2021; Geary, 2021; Hyde, 2005; Wizeman & Pardue, 2001; Wood
& Eagly, 2002; Zell, Krizan, & Teeter, 2015). An evolutionary explanation for these differences
relies on sexual selection theory.
Sexual selection occurs when one sex, usually the female, invests more in offspring, and the
other sex, typically the male, invests more in mating competition (Darwin, 1871; Janicke,
Häderer, Lajeunesse, & Anthes, 2016; Trivers, 1972). When applied to humans, sexual selec-
tion theory has produced many explanations and testable predictions regarding the reproduc-
tive benefits of males’competitive strategies, including direct competition, physical aggression,
risk-taking, showing off, impulsivity, sensation-seeking, and resource accumulation (Archer,
2009,2019; Walter et al., 2020). Because such behaviors can improve males’ability to succeed
in mating competition, they constitute part of an optimal strategy for fitness maximization
even when they reduce survival. Mating competition thus accounts for many “male traits”
(those that are expressed more in males than females).
In contrast to male traits, evolutionary theorists have tended to explain female traits in a
more piecemeal manner. At least four theories related to sexual selection commonly have
been applied to understanding female traits: mating competition, social selection, parental
investment, and (in humans) “staying alive”theory (SAT).
The mating competition component of sexual selection theory explains female traits as
adaptations for either defeating other females in conflicts over mates or being chosen as
mates by males (Janicke et al., 2016). In humans, a high-quality mate can enhance a woman’s
fitness through providing resources, protection, support, and/or good genes (Campbell, 2004).
Human females’competitive strategies to attract high-quality males rarely involve direct com-
petition, but instead rely more on self-promotion (Blake, Bastian, Denson, Grosjean, & Brooks,
2018; Puts, 2010) and indirect tactics including denigration of competitors’reputations and
social exclusion (Archer, 2004; Campbell, 2004; Hess, Helfrecht, Hagen, Sell, & Hewlett,
2010; Reynolds, 2021).
Social selection theory applied to females emphasizes contests against other females for
resources, territory, or allies (Clutton-Brock, 2007; Stockley & Bro-Jørgensen, 2010). Again,
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
direct contests are relatively uncommon in humans (Campbell,
2004). Instead, human females frequently compete for resources
and allies utilizing indirect tactics as in mating competition
(Björkqvist, 1994; Burbank, 1987; Campbell, 2004; Jankowiak,
Sudakov, & Wilreker, 2005; Rucas, 2017).
Parental investment theory focuses on how adults, typically
females, provide optimal levels of care for their young (Trivers,
1972). The theory examines adaptations that maximize produc-
tion and survival of offspring independent of mating relation-
ships, including optimizing interbirth intervals, manipulating
sex ratios, and aborting embryos or infanticide (Hrdy, 1981;
Trivers, 1974; Trivers & Willard, 1973). Parental investment
theory has been applied fruitfully to humans to explain diverse
patterns of mothering (Hrdy, 1999).
Building on parental investment theory, Campbell (1999)pro-
posed SAT. She posited that survival is more fitness-enhancing for
females than males, and therefore that human females more than
males evolved to avoid physical aggression and invest in alterna-
tive traits. Campbell (1999) emphasized “that lower rates of
aggression by women reflect not just the absence of male risk-
taking but are part of a positive female adaptation driven by the
critical importance of the mother’s survival for her own reproduc-
tive success”(p. 204). Campbell focused on fear as the critical
mechanism that protects females from injurious forms of aggres-
sion, and found that females indeed tend to be more fearful than
males.
Here we examine whether Campbell’s theory has more general
applicability by considering the hypothesis that compared to
males, human females respond with greater protectiveness to
other threats beyond aggression. We define threat as anything
potentially damaging to an individual’s survival.
Campbell’s(1999) assumption that survival is more fitness-
enhancing for females than males predicts that females tend to
outlive males. In support, despite large cultural variations, in virtu-
ally every country women outlive men as shown in Figure 1 for 2020
(Roser, Ortiz-Ospina, & Ritchie, 2013). A similar tendency for
females to live longer than males is found in mammals (Lemaître
et al., 2020).
SAT also predicts that the sex difference in longevity has
evolved at least partly because of the benefits that offspring receive
from female care, assuming that females contribute more than
males to offspring survival. Studies of contemporary societies
from hunter-gatherers to Western, Educated, Industrialized,
Rich, and Democratic (WEIRD) nations (Henrich, 2020) confirm
females’greater investment in and contribution to offspring sur-
vival (Atrash, 2011; Hawkes, O’Connell, & Blurton Jones, 2018;
Sear & Mace, 2008). According to Wood and Eagly’s(2002) anal-
ysis of 186 geographically and culturally diverse non-industrial
societies from the Human Relations Area Files, “all of the cultures
in our review revealed an alliance between men and women in a
division of labor, which appeared to be organized primarily to
enable mothers to bear children and nurse and care for infants”
(p. 718). Mothers were the principal caregivers of infants in
92% of these societies (and simultaneously of young children in
26–70% of these societies), whereas fathers and other men
never were. Further, across six hunter-gatherer or horticulturalist
societies, excluding nighttime co-sleeping, mothers took care of
infants between 46 and 53% of the day and fathers between 0
and 6%, with older siblings, grandmothers, and others comprising
the additional caregivers (Kramer, 2005).
Besides mothers, female kin, especially grandmothers and
older daughters, most often helped mothers with childcare
(Wood & Eagly, 2002). Grandmothers have been found to be
particularly important for increasing grandchildren’s survival,
more so than grandfathers (Hawkes et al., 2018; Lahdenpera,
Lummaa, Helle, Tremblay, & Russell, 2004; Sear & Mace, 2008).
A high adaptive value of grand-mothering is suggested by eight
mammalian species in which females contribute to caring for
their grand-offspring, because females’lifespans in those species
averaged 43% longer than males, compared to only 8% longer
in related species without grand-mothering (Péron et al., 2019).
Older daughters also help mothers (Bove, Valeggia, & Ellison,
2002; Kramer, 2005; Whiting et al., 1988). Across 13 traditional
societies, girls were more likely than boys to assist in direct care
for younger siblings (Whiting et al., 1988). In six hunter-gatherer
or horticulturalist societies, girls cared for younger siblings
between 13 and 33% of the day, with boys childminding 1–14%
of the day (Kramer, 2005). In WEIRD societies where children
rarely care for younger siblings, girls more than boys cared for
dolls (d= 4.12) (Davis & Hines, 2020). In non-human primates,
preadult females also attend to and hold infants more than
males do (Benenson, 2019).
These data support the idea that the greater longevity of
females than males is an evolutionary response to women’s larger
role in childcare, such that at all ages selection tends to favor
female survival. Thus, females and males confront different life
history tradeoffs, with the sex that cares for offspring investing
more in survival (Hamilton, 1966; Kirkwood & Rose, 1991;
Trivers, 1972; Williams, 1966). Preliminary evidence in mammals
also links higher female longevity with greater female, relative to
male, parental care (Allman, Rosin, Kumar, & Hasenstaub, 1998).
JOYCE F. BENENSON is a lecturer in the Department of Human
Evolutionary Biology at Harvard University. She studies the develop-
ment of sex differences in human social structure, focusing on compe-
tition and cooperation from infancy through adulthood. Much of her
research is based on findings with non-human primates, particularly
chimpanzees. She has been a professor in the United States, Canada,
and England, published over 80 articles including her book, Warriors
and Worriers, and is a Fellow of the Association for Psychological
Science.
CHRISTINE E. WEBB is a Lecturer in the Department of Human
Evolutionary Biology at Harvard University. She is a broadly trained
primatologist and psychologist with expertise in social behavior,
motivation, and emotion. Her main interests include how humans
and other primates manage and mitigate conflicts, including the soci-
oemotional mechanisms –like empathy –that motivate these pro-
cesses. She also collaborates with philosophers to reconsider the
role of science in the “animal turn,”and is working on a book project
that critically engages with anthropocentrism in comparative
research.
RICHARD W. WRANGHAM is the Moore Research Professor of Biological
Anthropology in the Department of Human Evolutionary Biology at
Harvard University, where he taught between 1989 and 2020. His
major interests are chimpanzee and human evolutionary ecology, the
evolutionary dynamics of violence and non-violence, and ape conser-
vation. Since 1987 he has studied wild chimpanzee behavior in Kibale
National Park, Uganda. His books include Catching Fire: How Cooking
Made Us Human (Basic Books, June 2009) and The Goodness Paradox:
The Strange Relationship Between Virtue and Violence in Human
Evolution (Pantheon, January 2019).
2 Benenson et al.: Self-protection as an adaptive female strategy
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
To evaluate the applicability of Campbell’s(1999) theory to
threats beyond aggression, we searched for articles that analyzed
sex differences in response to major threats to survival: internal
and external physical dangers, social conflicts, personality styles,
emotional reactions to threat, and threat-related clinical
conditions. We surveyed highly cited reviews, meta-analyses,
and articles that examined human sex differences with large
samples from diverse countries, along with authoritative refer-
ences such as the World Health Organization (WHO) and the
Diagnostic and Statistical Manual of Mental Disorders 5
th
edition
(DSM-V). We report sample sizes, effect sizes based on Hyde’s
(2005) cutoffs, and developmental effects when these were avail-
able. Because many fewer elderly men than women are alive
thereby introducing confounds into sex-based comparisons, we
focused on young and middle-aged adults. Further, because
female investment in childcare increases sharply after puberty,
we predicted increased magnitudes of sex differences following
puberty and searched for evidence comparing children with ado-
lescents. We included only high-quality datasets for each kind of
threat and searched for inconsistencies with other published find-
ings. Following Campbell (1999), we included only self-protective
reactions to threat, rather than reactions that increase the potential
for harm, such as impulsivity, sensation-seeking, risk-taking, direct
aggression, or homicide which are well-known to be less common
in females than males (Archer, 2019). Additionally, we reviewed
Hyde’s(2005), Zell et al.’s(2015), and Archer’s(2019)meta-
analytic summaries of sex differences to identify any additional
protective reactions to threats or contrary findings. All sex differ-
ences we report were statistically significant unless otherwise stated.
We recognize that human sex is a multidimensional construct
influenced by the continuing interplay of biological and environ-
mental components and that the studies we found are limited by
including only binary comparisons (Berenbaum & Beltz, 2021;
Eliot, 2009; Fausto-Sterling, 2019; Hyde, Bigler, Joel, Tate, &
van Anders, 2019). We also acknowledge that many sex differ-
ences in specific traits are small, so that sex stereotypes based
on single traits mischaracterize the large overlap between the
sexes (Hyde, 2005; Zell et al., 2015). Our goal is to suggest that
many female-associated traits, which are often pathologized in
comparison to male-related traits, can more appropriately be con-
sidered, like most evolved features, to enhance females’survival
and reproductive success.
2. Protective responses to physical threat
According to our extension of SAT, females should protect them-
selves more than males in response to all physical threats. We
therefore tested the hypothesis that females exhibit stronger
defenses than males against pathogens, bodily damage, and envi-
ronmental dangers.
Recent cross-cultural evidence shows that females were less
likely than males to die from disease at every age. The major causes
Figure 1. United Nations data for life expectancy by sex for 2020.
Source: UN Population Division (2019 Revision).
Note: Shown is the period life expectancy at birth measured in years.
Benenson et al.: Self-protection as an adaptive female strategy 3
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
of sex differences in mortality worldwide are shown in Figure 2
with disease the most common contributor (WHO, 2018).
Excluding reproductive-related conditions, the fatal illnesses
that contributed most to reducing life expectancy afflicted females
less frequently or later in life than males (Austad, 2006;
Verbrugge, 1985). Thus, females were less likely than males to
develop many diseases, including malaria, leptospirosis, schistoso-
miasis, brucellosis, rabies, leishmaniasis, pulmonary tuberculosis,
hepatitis A, meningococcal and pneumococcal infections
(Giefing-Kröll, Berger, Lepperdinger, & Grubeck-Loebenstein,
2015; Mihailova & Krams, 2018).
When females developed fatal diseases, they died later than
males with small to moderate effect sizes. As examples, adjusting
for age, worldwide in 2021 the odds of dying from lung (OR =
0.46), colorectal (OR = 0.68), and stomach (OR = 0.45) cancer
were lower for women than men (WHO, 2021). In the United
States in 2007, the age-adjusted odds of dying from cardiovascular
disease (CVD) were lower for females than males (OR = 0.70)
(Mosca, Barrett-Connor, & Kass Wenger, 2011). In the United
States in 2010, females’age-adjusted death rate was lower than
males’for 12 of the most frequent 15 diseases. Two were equal,
while only Alzheimer’s disease killed more women than men
(Austad & Bartke, 2016). Mortality from the coronavirus
disease-2019 (COVID-19) pandemic epitomizes the overall pat-
tern: In 37/38 countries fewer women than men died (Scully,
Haverfield, Ursin, Tannenbaum, & Klein, 2020) with an effect
size (OR = 0.63) (Williamson et al., 2020). Sex differences in fatal-
ity rates from COVID-19 appeared even in mice (Scully et al.,
2020). Overall, therefore, females are better protected than
males from death by disease.
2.1. Immune defenses
Since immune activation is necessary for survival, SAT predicts
that females should exhibit more effective immune responses
than males. This prediction is upheld in vertebrates generally.
Across most vertebrate species, females are better able than
males to defend themselves against a majority of environmental
and vector-borne threats, including fungi, viruses, bacteria, para-
sites, and allergens, as well as internal threats such as tissue dam-
age and tumors (Giefing-Kröll et al., 2015; Klein, 2000; Klein &
Flanagan, 2016; Oertelt-Prigione, 2012; Ortona, Pierdominici, &
Rider, 2019). Females’immune systems also respond better than
males’to trauma, sepsis, and shock (Angele, Frantz, & Chaudry,
Figure 2. Sex differences in diseases that are major causes of death
worldwide from the World Health Organization.
Source: WHO (2018)(2) and see (4) for composition of life expec-
tancy. © Reprinted with permission from the World Health
Organization.
4 Benenson et al.: Self-protection as an adaptive female strategy
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
2006; Angele, Pratschke, Hubbard, & Chaudry, 2014). In response
to injury, estrogen administration has been shown to promote
healing by upregulating the immune system and reducing mor-
bidity and mortality (Angele et al., 2014; Bösch, Angele, &
Chaudry, 2018). The American National Health and Nutrition
Examination Survey (n= 38,000) from 1988 to 2006 of demo-
graphically representative adults showed that women exhibited a
stronger immune response than men, as indicated by a higher
inflammatory rate, with a large effect size (OR = 4.17) (Yang &
Kozloski, 2011).
The immune system functions in two waves (Roved,
Westerdahl, & Hasselquist, 2017). First, the general, continually
active, costly, rapid, innate part of the immune system responds
to a new infection or inflammation. Second, cytokines released
by the innate immune system ramp up the adaptive immune sys-
tem through increased cell-mediated T and humoral-situated B
cells which are capable of remembering specific antigens, thereby
creating longer-term protection. The type of adaptive immune
response varies with T-helper (Th) cells, with one type (Th1,
Th2, or Th17) increasing at the expense of another. Th1 immune
cells typically produce pro-inflammatory responses that clear
infections, whereas Th2 cells produce anti-inflammatory immune
responses.
Part of the reason for female mammals’stronger immune
response is that the X chromosome encodes more immune-
related genes than the Y chromosome, and females have two X
chromosomes while males have only one (Klein & Flanagan,
2016). Further, in females, one X chromosome typically is
randomly inactivated in each cell meaning that females are mosa-
ics permitting increased transcription by both X chromosomes to
contribute to immunity. Additionally, some X chromosomes
escape inactivation also providing extra immunity (Takahashi &
Iwasaki, 2021). In mice, experimentally adding an X chromosome
to an XY individual to create an XXY individual increases longev-
ity (Davis, Lobach, & Dubal, 2019).
Another reason for females’stronger immune defenses is their
higher estrogen and lower androgen levels. Estrogens intricately
regulate immunity by both stimulating and suppressing differing
types of immune cells, while androgens generally reduce immune
functioning (Foo, Nakagawa, Rhodes, & Simmons, 2017; Klein &
Flanagan, 2016; Roved et al., 2017). Differing concentrations of
estrogens can regulate the balance between T-helper cells-2
(Th2) and Th1 and Th17 cells. In contrast, androgens reduce
Th2 and Th17 immune processes.
Estrogen levels are not solely responsible for enhanced immu-
nity however, because even pre-pubertal girls activated stronger
innate responses than boys, though some sex differences did not
appear until puberty (Klein & Flanagan, 2016). After puberty,
more components of both the innate and adaptive immune sys-
tems were upregulated in women than in men.
Some of the clearest evidence for females’stronger inflamma-
tory response comes from reactions to vaccinations. In response
to most vaccinations including influenza, pneumonia, hepatitis
A and B, tetanus, diphtheria, measles, meningitis, rabies, yellow
fever, and smallpox, especially after puberty, human females gen-
erally produced more antibodies, and experienced more side
effects including fever, soreness, and redness, than males
(Flanagan, Fink, Plebanski, & Klein, 2017; Klein, Jedlicka, &
Pekosz, 2010). Immune responses were more suppressed in
older individuals, but the suppression developed more slowly in
women than men. Immune responses to vaccines were so much
stronger in women than men that for a number of vaccines,
half the dose of a vaccination in women caused the same level
of antibodies as a full dose in men (Giefing-Kröll et al., 2015).
While ceiling effects in vaccine efficacy obscure sex differences,
when differences appeared, vaccines were more effective in
females (Flanagan et al., 2017). However, when vaccine doses
were too strong, females were more likely to die from the vaccine
(Flanagan et al., 2011), as happened in some African infant inoc-
ulation campaigns (Aaby et al., 2020). Further, a higher concen-
tration of circulating estrogens was positively related to stronger
responses to vaccines in humans and mice (Aaby et al., 2020).
Table 1 summarizes some of the human findings (Flanagan
et al., 2017).
Results with mice demonstrated causality. In mice inoculated
against H1N1, females produced more robust IgG and IgA anti-
bodies and B cells and higher quality antibodies than males.
When these mice were infected with H1N1, females became less
sick, had a lower viral load in their lungs, and recovered more rap-
idly than males (Fink, Engle, Ursin, Tang, & Klein, 2018).
Observations of people infected with COVID-19 similarly showed
that women with higher antibody levels tended to be less sick
(Takahashi et al., 2020).
Pregnancy illustrates the strength of the immune system in
non-pregnant women. During pregnancy, myriad changes occur
in the innate and adaptive immune systems that affect maternal
and fetal responses to pathogens (Abu-Raya, Michalski,
Sadarangani, & Lavoie, 2020). A pregnant woman’s immune sys-
tem must find an optimal way to balance ensuring survival of the
genetically foreign fetus with protecting herself and the fetus from
pathogens. One way this occurs is by downregulating Th1 cells
producing pro-inflammatory cytokines. This switches the prepon-
derance to Th2 cells producing anti-inflammatory cytokines. Sex
hormones, including estrogens and progesterone, regulate the bal-
ance between Th1 and Th2 lymphocytes so that across pregnancy
proinflammatory responses diminish and anti-inflammatory
responses increase (Robinson & Klein, 2012).
The result is that pregnant women are more susceptible than
non-pregnant women to, and/or suffer more severe, including
fatal, reactions to infections from pathogens, including malaria,
tuberculosis, influenza, hepatitis E, invasive pneumonia, herpes
simplex virus, Ebola, and measles. In contrast, the severity of
inflammatory diseases such as multiple sclerosis and arthritis is
reduced (Abu-Raya et al., 2020). Increased maternal morbidity
and mortality during pregnancy also occurred with recent severe
acute respiratory viruses (H1N1, SARS, and MERS) (Schwartz,
2020), including COVID-19 (Zambrano et al., 2020).
Stronger activation of non-pregnant females’immune system
however has a downside labeled “the health-survival paradox.”
Despite their greater longevity, women felt sicker and were diag-
nosed with more illnesses than men across North America and
Europe, and in Egypt, China, Indonesia, Mexico, and the
Tsimane of Bolivia (Alberts et al., 2014; Austad & Bartke, 2016;
Christensen, Doblhammer, Rau, & Vaupel, 2009; Khadr &
Yount, 2012; Macintyre, Ford, & Hunt, 1999; Mirowsky & Ross,
1995; Roved et al., 2017; Wheaton & Crimmins, 2016).
Older women from culturally diverse societies, including the
Tsimane of Bolivia, Taiwan, Korea, Mexico, China, Indonesia,
reported being sicker and weaker and were evaluated objectively
by medical personnel and researchers to be in poorer health
than men.
“For instance, women in high-income countries are more likely than men
to report difficulties in walking, climbing stairs, dressing, and other
Benenson et al.: Self-protection as an adaptive female strategy 5
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
common activities. In low-income countries, women report greater diffi-
culties than men in a wide range of common activities such as bending
over, pumping water, or walking a specified distance. In addition,
women make more doctor visits, spend more days hospitalized, and
take more medications than do men. Even in Russia, which has one of
the largest sex differences in life expectancy in the world, with a male dis-
advantage of more than 10 years, males report better health and physical
functioning at ages of 55 years and higher.”(Austad & Batke, 2016, p. 42).
In twentieth-century American nationwide statistics, at all
ages women experienced fewer fatal conditions than men, but
suffered from more frequent daily symptoms, and more acute
(except for injuries) and chronic and disabling conditions as
diagnosed by doctors and in hospitals. The sex difference was
largest during young adulthood, even after all reproduction-
related conditions were excluded. Women reported more daily
symptoms, more days with symptoms, more days in bed,
more disability days, more health problems across more
bodily systems, more prescription drug use, more alternative
care visits, and more frequent discussions about their health
problems with family and friends (Verbrugge, 1976,1985,
1986,1989).
The sex difference in the prevalence of immune activation
increased at puberty but appeared by early childhood. In a large
study of Norwegian adolescents (n= 10,000, ages 17–19 years),
47% of girls versus 21% of boys (OR = 3.34) reported at least
one weekly health complaint (Myrtveit Sæther, Sivertsen,
Haugland, Bøe, & Hysing, 2018). Two weekly health complaints
were reported by 30% of girls and 10% of boys (OR = 3.86).
Employing the Health Behaviour in School-Aged Children
(HBSC) scale, a WHO study in 32 countries in Europe and
North America plus Israel (n= 1,500 each nation at ages 11, 13,
and 15 years, n> 150,000) found that girls reported poorer
general health than boys at ages 11 (OR = 1.36), 13 (OR = 1.68),
and 15 years (OR = 1.97) (Cavallo et al., 2006). Likewise in
the Avon Longitudinal Study of Parents and Children
(ALSPAC) (n> 13,900), pregnant women in 1991–1992 in
Southwestern England were recruited and later asked to report
symptoms experienced by their 4–13-year-old children
(Sweeting, Whitley, Teyhan, & Hunt, 2017). From 4 years
onwards, more girls than boys experienced colds, cold sores,
tonsillitis, urinary infections, earaches, headaches, stomach-
aches, worm infections, head lice or scabies, constipation,
and eczema. Beginning at age 7, more girls than boys experi-
enced rashes, and by 10 years, more girls than boys developed
fevers, ear and eye infections, and were struggling with poorer
overall health. In contrast, in childhood, boys were more likely
thangirlstosufferchestinfections, breathlessness, wheezing,
asthma, hay fever, pain in legs and joints, and diarrhea. After
puberty, most of boys’excess health problems disappeared
with girls then experiencing these problems equally or more
frequently.
In summary, evidence supported the hypothesis that with the
exception of pregnancy, human females mounted stronger and
longer-lasting immune responses than males.
Table 1 Sex differences in immune responses and adverse reactions to vaccinations over the lifespan.
Sex differences in acceptance, immune responses, and adverse reactions to vaccines in humans
Target group Vaccine
Gender difference
in acceptance
Sex difference in
immune response
Sex and gender difference
in adverse reactions Age (years)
Children Hepatitis B Not defined Greater in females Not defined <12
Diphtheria Not defined Greater in females Not defined <2
Pertussis Not defined Greater in females Not defined <2
Pneumococcal Not defined Greater in females Not defined 6–9
Rabies Not defined Greater in females Not defined 6–9
Measles Not defined Greater in females or
equivalent in both sexes
Increased in females <3
Malaria (RTS.S) Not defined Greater in females Increased in females <2
Human papillomavirus Less in males Greater in females Increased in females 5–17
Adults Influenza Less in females Greater in females Increased in females 18–49
Hepatitis B Not defined Greater in females Increased in females 18+
Herpes virus Not defined Greater in females Not defined 18+
Yellow fever Not defined Greater in females Increased in females 18+
Rabies Not defined Greater in females Not defined 18+
Smallpox Not defined Greater in females Not defined 18+
Aged adults Influenza Less in females Greater in females Increased in females 65+
Td/Tdap Less in females Greater in males Increased in females 65+
Pneumococcal Less in females Greater in males Increased in females 65+
Shingles Not defined Not defined Increased in females 65+
© Used with permission of Annual Reviews, Inc. from Sex and Gender Differences in the Outcomes of Vaccination over the Life Course, Katie L. Flanagan et al., 33, 2017, permission conveyed
through Copyright Clearance Center, Inc.
6 Benenson et al.: Self-protection as an adaptive female strategy
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
2.2. Preventing injury through the sensation of pain
Pain signals potential danger or actual damage typically following
inflammation or trauma (Eisenberger & Lieberman, 2004). It
therefore constitutes a critical self-protective warning mechanism
and ongoing monitoring system that impels corrective action to
protect an organism (Grahek, 2001). A heightened sensation of
pain should reduce the prevalence of injury and repair damage
from an already sustained injury by behaviorally removing or
reducing pain-inducing stimuli, thereby enhancing survival. We
therefore searched the literature to test the hypothesis that females
experience greater pain than males.
Fillingim, King, Ribeiro-Dasilva, Rahim-Williams, and Riley
(2009) reviewed clinical and experimental pain studies across
diverse countries including rural Brazil, India, Nigeria, Turkey,
as well as in European and North American nations. They
found that in their daily lives, more women than men reported
higher pain prevalence at all sites in the body in the prior week
or day, including oral, abdominal, and head pain. Women expe-
rienced pain more than men from a variety of sources and across
multiple bodily sites, including from cancer, neuropathic, muscu-
loskeletal, and back pain. Likewise in a detailed study of 11,000
patients with 47 diagnoses in an American hospital, patient-
reported or practitioner-rated pain scores were higher for
women than men for the same diagnosis as pictured in
Figure 3 (Ruau, Liu, Clark, Angst, & Butte, 2012).
The same sex difference appeared also for chronic, widespread
pain. Mansfield, Sim, Jordan, and Jordan (2016) reviewed studies
of chronic widespread pain in diverse countries including North
and South America, the Middle East, Europe, Oceania, and
Asia. Chronic widespread pain was reported more frequently by
women than men on average by a 2:1 margin with large variation
across ages and cultures and female:male ratios ranging from 1.06
to 4.80.
Even during simple intramuscular injections, women experi-
enced more pain than men (Fillingim et al., 2009). While this
may be partially due to women’s lower muscle density and tissue
mass, even 5-year-old girls reported more pain than boys to veni-
puncture (Chambers, Giesbrecht, Craig, Bennett, & Huntsman,
1999).
Sex differences in pain emerge in childhood. The WHO HBSC
study in 32 countries in Europe, North America, and Israel (n>
150,000) found that more girls than boys experienced headaches
at age 11, 13, and 15 years respectively (ORs = 1.44, 1.88, 2.70),
stomachaches (ORs = 1.64, 2.00, 2.31), and backaches (ORs =
1.16, 1.24, 1.28) (Cavallo et al., 2006). Likewise, the English
ALSPAC study found that beginning with the youngest children
in their study (age 4 years), girls reported more headaches, stom-
achaches, and earaches than boys did (Sweeting et al., 2017).
Chronic pain also was reported in childhood by females more
than males (Fillingim et al., 2009).
Similar sex differences in responses to pain were found in mice
and rats (Mogil, 2020). Rodent studies of the midbrain periaque-
ductal gray and the spinal cord showed that pain and analgesics
are modulated differently in females than males (Shansky &
Murphy, 2021).
In experimental studies that induce pain using identical stim-
uli, women consistently responded to bodily injury faster and
endured it less long than men did across multiple bodily sites
and modalities of inflicting pain (Fillingim et al., 2009). In a
meta-analysis of pain threshold (n> 1,600) and pain tolerance
(n> 41,500) for pressure, heat, electrical shock, and ischemic
induced pain, women endured pain at a lower stimulus intensity
(d= 0.51) and for a shorter time period (d= 1.17) than men did,
yielding moderate to large effect sizes (Riley, Robinson, Wise,
Myers, & Fillingim, 1998). The sex difference in pain diminished
in old age but never disappeared (Girotti et al., 2019).
In experimental tests with children, a meta-analysis showed
few sex differences (Boerner, Birnie, Caes, Schinkel, &
Chambers, 2014). Overall, no sex differences were found in
responses to pain intensity, and only 31% of studies found that
girls exhibited lower pain thresholds than boys. Some specific
types of pain, such as pain due to heat however, produced the
same sex differences as in adolescents and adults.
In sum, adult females routinely experience greater pain than
males. This suggests that a stronger experience of pain constitutes
a female adaptation that functions to enhance survival through
reducing injury. In support, the Global Burden of Disease find-
ings showed that disability-adjusted lost years (DALYs) from all
types of injuries were typically lower for females than males for
ages 15–49 years, as displayed in Figure 4 (Haagsma et al., 2016).
The sex difference was smaller but in the same direction for
children 0–14 years. From 1990 to 2017, the same sex difference
for adults in DALYs appeared globally for child injuries from all
causes except heat (James et al., 2020). Likewise, in the WHO
HBSC study with 15-year-olds in 36 European and North
American countries, girls reported fewer injuries overall than
boys in the prior year and fewer physical fights (de Looze,
Elgar, Currie, Kolip, & Stevens, 2019).
2.3. Countering nighttime threats through frequent awakening
Nighttime is a dangerous period because threats are not easily
detected. Increased nighttime vigilance improves detection of
Figure 3. Average pain scores by sex for 47 conditions from one American hospital. ©
Reprinted from the Journal of Pain, 13/3, Ruau et al., Sex Differences in Reported
Pain Across 11,000 Patients Captured in Electronic Medical Records, Pages 228–
234, 2012, with permission from Elsevier.
Benenson et al.: Self-protection as an adaptive female strategy 7
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
physical and social threats, including intruders, predators, and
fire, that could elude identification during sleep. Accordingly,
we tested the prediction from SAT that females are more attuned
than males to nighttime threats.
We found that worldwide women reported being awake at
night more often than men did. The American Society for
Women’s Health Research concluded that women’s sleep differed
objectively and subjectively from men’s (Mallampalli & Carter,
2014): women experienced more slow wave sleep and less
non-REM sleep than men. Women also experienced longer
sleep latency and reported feeling sleepier than men. Further,
across humans, mice, and rats, sex hormones affected females’
more than males’sleep (Hajali, Andersen, Negah, & Sheibani,
2019; Mallampalli & Carter, 2014).
A meta-analysis (n>1.2million,ages15–103 years) from diverse
countries of sex differences in sleep disturbances illustrated the
findings: In 26 of 29 studies, at all ages women reported more fre-
quent nighttime awakening than men (risk ratio = 1.41) (Zhang &
Wing, 2006). The Chinese Henan Rural Cohort Study (n> 27,000,
ages 18–79 years) employing the Pittsburgh Sleep Quality Index
found that females experienced lower sleep quality than males
with effect sizes ranging from negligible to small for subjective
sleep quality (d=−0.20), sleep latency (d= 0.21), sleep duration
(d=−0.03), sleep efficiency (d=−0.13), sleep disturbance (d=0.15),
use of sleep medication (d= 0.08), daytime dysfunction (d=0.08),
and generally (d=0.22)(Wangetal.,2019).
Globally, following puberty women had a 40% higher risk than
men of developing insomnia during their lifetimes as depicted in
Figure 5 (Mong & Cusmano, 2016).
Furthermore, a meta-analysis (n> 180,000) showed that more
females than males experienced nightmares with negligible to
small effect sizes in adolescents (Hedge’sg= 0.22), young adults
(g= 0.26), and in middle age (g= 0.15). The sex difference was
not significant for children (g=−0.03), or >60 years (g= 0.10)
(Schredl & Reinhard, 2011).
Although sex differences in nighttime awakenings were negli-
gible to small for children, they increased with age and pubertal
status. In the 32 country WHO HBSC survey, girls reported
increasing sleep difficulties relative to boys at 11, 13, and 15
years of age (ORs = 1.13, 1.36, 1.56, respectively) (Cavallo et al.,
2006). A study in Hong Kong (n> 7,500 ages 6–17 years) linked
pubertal development to specific sleep disturbances (Zhang et al.,
Figure 4. Disability-adjusted life year (DALY) by injury, sex, and region for ages 15–49 years from the Global Burden of Disease project. DALY rates per 100000. CC
BY-NC 4.0
8 Benenson et al.: Self-protection as an adaptive female strategy
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
2016). Children and adolescents, and their caregivers, reported
that girls developed more overall insomnia, difficulty initiating
sleep, and difficulty maintaining sleep than boys as they entered
pubertal stage 4 on the Tanner scale, although they already had
experienced more difficulties with early morning awakening as
displayed in Figure 6.
Overall, evidence supported the hypothesis that females expe-
rienced more nighttime awakenings than males. This is consistent
with the hypothesis that nighttime awakenings constitute a female
adaptation that enhanced self-protection during an interval of
heightened vulnerability.
We also noted that women were less likely than men to suffer
from severe, potentially fatal sleep disorders including narcolepsy,
obstructive sleep apnea, and hypoventilation (Hajali et al., 2019;
Lévy et al., 2015). Furthermore, laboratory studies of sleep indi-
cated that length, depth, and efficiency of sleep, including
enhanced slow wave sleep and slow wave activity, were higher
in women than men (Hajali et al., 2019; Mong & Cusmano,
2016; Suh, Cho, & Zhang, 2018). While these observations are
limited to Western research, they suggest that females might com-
pensate for their more frequent awakenings by maintaining a
superior quality of sleep.
2.4. Miscellaneous physical threats
Innumerable external physical stimuli threaten survival. We tested
the hypothesis, derived from SAT, that females would be more
effective than males at avoiding or reducing such threats. We
were able to locate evidence for three types of threat: hypothetical
physical threats, long-term environmental degradation, and major
disease outbreaks.
In the standardized International Affective Picture System
(IAPS), participants evaluated the valence of photographs of non-
human animals, scenes, and inanimate objects. In the United
States, Germany, Switzerland, and China, girls and women
reported stronger aversion than their male counterparts to all rep-
resented threats, including accidents, illness, pollution, and dan-
gerous animals (Bradley, Codispoti, Sabatinelli, & Lang, 2001;
Lang & Bradley, 2007) with moderate to large effect sizes in adults
(d= 0.36) (Gomez, von Gunten, & Danuser, 2013), (d= 0.55)
(Gong, Wong, & Wang, 2018)(d= 0.43 and 0.80) (McManis,
Bradley, Berg, Cuthbert, & Lang, 2001), and in children (d=
0.64 and 0.67) (McManis et al., 2001).
Similar sex differences have been found in response to
environmental dangers. In the International Social Survey
Programme (ISSP) administered in 1993 and 2000 in 26 countries
from Asia, Eastern and Western Europe, North and South
America, and Oceania (n> 23,000), women expressed more con-
cern about the state of the environment than men did (Franzen &
Meyer, 2010). Between 2009 and 2011, an expanded ISSP in 32
nations in Africa, Asia, Europe, North and South America, and
Oceania (n> 45,000) showed that women exhibited more positive
views than men toward protecting the environment, greater
awareness of environmental problems, and more willingness to
pay to correct environmental problems (Chan, Pong, & Tam,
2019).
With regard to major outbreaks of disease, a review with
Asian, European, and North American participants (n> 25,000,
12 countries) showed that during disease outbreaks women
reported being more likely than men to adopt avoidant and pro-
tective measures, including handwashing, wearing a mask, and
quarantining (Bish & Michie, 2010). Across eight OECD coun-
tries (n> 20,000), women were more likely than men to have per-
ceived COVID-19 as a serious health risk and to have complied
with restraining public health rules (Galasso et al., 2020).
Nonetheless, women can be more reluctant than men to
receive vaccines, most likely because of the more adverse side
effects of vaccines in women than men (Flanagan et al., 2017).
A review (37 studies, 15 diverse countries) of reactions to the
2009 strain of H1N1 influenza showed that both women in the
general population and female health care professionals indicated
they would be less likely than their male counterparts to be vac-
cinated (Bish, Yardley, Nicoll, & Michie, 2011). An explanation
proposed by Bish et al. (2011) was that women tended to believe
that the immediate negative effects of the vaccine outweighed its
health benefits, consistent with greater side effects in women. A
similar concern about negative effects might explain a meta-
analysis (n= 88 studies) with African, Asian, Australian,
European, North and South American samples, which found
that women were 50% more likely than men to have adopted non-
pharmacological prevention and avoidant measures in reaction to
respiratory pandemics (OR = 1.49), whereas men were slightly
more likely to take pharmaceutical protections (OR = 0.89)
(Moran & Del Valle, 2016).
Overall, for the environmental threats we examined, women
reacted more protectively than men with small to large effect
sizes, consistent with a female adaptation for increasing longevity.
3. Protective responses to social threat
Social threat includes at least two distinct types: conflicts and iso-
lation. Social conflicts can be physically dangerous, potentially
leading to fights, reputation denigration, ostracism, expulsion,
and even capital punishment (Boehm, 1999; Wrangham, 2019).
Social isolation predicts psychological and physical morbidity
and mortality in young, middle-aged, and elderly adults in a dose-
dependent manner (Hawkley & Cacioppo, 2010). A meta-analysis
of longitudinal studies (n> 3.4 million) showed that objective
measures of both social isolation and feeling lonely predicted
increased mortality (OR = 1.26–1.83) (Holt-Lunstad, Smith,
Baker, Harris, & Stephenson, 2015). The longer the loneliness,
Figure 5. Prevalence of insomnia by sex and age. © Used with permission of The
Royal Society from Sex differences in sleep: Impact of biological sex and sex steroids,
Jessica A. Mong and Danielle M. Cusmano, 371, 2016, permission conveyed through
Copyright Clearance Center, Inc.
Benenson et al.: Self-protection as an adaptive female strategy 9
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
the greater the risk. Even experimentally inducing feelings of
loneliness increased stress and feelings of danger (Holt-Lunstad
et al., 2015).
Conversely, it is well known that social ties increase survival.
A meta-analysis of longitudinal findings from Asia, Australia,
Europe, and North America in community and patient samples
(n> 300,000) showed that across sex, age, initial health status,
and cause of death, social integration increased survival by 50%,
and by 91% using multiple measures of integration (Holt-
Lunstad, Smith, & Layton, 2010). Similarly, in a large study in
Asia, Europe, and North America (n> 7.5 million), not being mar-
ried increased all-cause mortality in both sexes, more for males
(risk ratio = 1.46) than females (risk ratio = 1.22) (Wang et al.,
2020).
SAT would predict that females tend to avoid conflicts and
promote social ties more than males do. We found relevant evi-
dence for four strategies that reduce negativity in interactions
and facilitate positive connections, namely smiling, politeness,
emotion identification, and avoidance of confrontations.
3.1. Smiling
Evidence indicates that women smile more than men with small
to moderate effect sizes. A meta-analysis of 162 studies (n>
100,000, 13 countries, 6 continents) reported greater smiling by
women from adolescence through old age in every country (d=
0.41) (LaFrance, Hecht, & Paluck, 2003). Sex differences were
greater in same-sex pairs (d= 0.48) than mixed-sex pairs (d=
0.35). Sex differences also were larger in contexts with greater
social tension (d= 0.47) than little tension (d= 0.20), and when
participants were unfamiliar (d= 0.45) rather than familiar (d=
0.24). This suggested that an important function of smiling was
to reduce threats from other individuals. Prior meta-analyses
also concluded that women’s smiles more than men’s function
to reduce social tension (Hall & Halberstadt, 1986).
Computerized coding likewise showed that women smiled
more than men. Analyses of photographs of Asian, Black, and
White New York City residents posted to Instagram and
Twitter (n> 15,000) demonstrated that the more females in a pic-
ture, the more smiling occurred as coded by automated software
(Singh, Atrey, & Hegde, 2017). Software similarly found that in
Argentina, Brazil, China, Colombia, France, Germany, India,
Japan, Mexico, Peru, Russia, the United Kingdom, and the
United States (n> 740,000), when watching television advertise-
ments women smiled more than men (McDuff, Girard, & El
Kaliouby, 2017). Sex differences in smiling however were not
found in children (Else-Quest, Hyde, Goldsmith, & Van Hulle,
2006).
Figure 6. Rates of insomnia in Hong Kong by sex and Tanner stage for (A) overall insomnia symptoms, (B) difficulty initiating sleep, (C) difficulty maintaining sleep,
and (D) early morning awakening. © Jihui Zhang et al., Emergence of Sex Differences in Insomnia Symptoms in Adolescents: A Large-Scale School-Based Study,
Sleep, 2016, 39, 8, 1563–1570, by permission of Oxford University Press.
10 Benenson et al.: Self-protection as an adaptive female strategy
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
3.2. Politeness
SAT would predict that females would be more likely than males
to speak politely since this should reduce interpersonal conflicts.
We tested the hypothesis that females more than males employed
polite language.
Evidence indicated that females exhibited greater politeness
than males with small to moderate effect sizes. In a meta-analysis
in primarily WEIRD countries (n> 3,500, 29 studies), women
used more tentative language (hedges, expressions of uncertainty,
intensifiers, and tag questions) than men (d= 0.23), which the
authors interpreted as seeking the listener’s consent (Leaper &
Robnett, 2011). Ethnographic reports from Africa, Europe, North
and South America, and Oceania also reported that girls and
women used more tentative speech than boys and men by employ-
ing more qualifiers, euphemisms, and apologies, and speaking with
less assertiveness, more agreement, higher numbers of softeners
and compliments, and greater supportiveness and modesty
(Brown & Levinson, 1987; Coates, 2015; Guadagno & Cialdini,
2007;Haas,1979; Holmes, 1989; Lakoff, 1975; Locke, 2011).
The same type of sex difference in the use of language has reg-
ularly been found in early childhood. In a meta-analysis of speech
forms in WEIRD cultures (46 studies, n> 2,600), girls made more
general affiliative comments (d= 0.26) than boys which was even
stronger in unstructured contexts (d= 0.58) (Leaper & Smith,
2004). Ethnographic reports in 13 non-WEIRD societies likewise
indicated that in middle childhood girls use more prosocial and
less egoistic dominance in their speech (Whiting et al., 1988).
3.3. Identification of others’emotions
Accurately identifying another’s emotions facilitates interactions
by enhancing understanding of the actor’s emotional state. SAT
would predict that females would be more likely than males to
accurately identify another’s emotions.
Studies utilizing primarily pictures or short videos of non-
verbal facial, bodily, and vocal behavior consistently demonstrated
that from early in life females detected social signals more accu-
rately than males did with small to moderate effect sizes. A meta-
analysis (75 studies, 1923–1978) with WEIRD and non-WEIRD
societies showed that girls and women were better able than
boys and men to accurately detect others’non-verbally expressed
emotions (d= 0.40) (Hall, 1978). A follow-up review demon-
strated that across cultures, ages, and target sex, girls and
women were better able than boys and men to accurately detect
the emotional valence of non-verbal facial and bodily behaviors,
as well as verbal intonation and prosody (d= 0.41–0.54) (Hall,
Carter, & Horgan, 2000). A more recent meta-analysis showed
that in 67% of 32 studies, women were more accurate than men
in identifying the valence of emotions, whereas no sex differences
occurred in the remainder (Forni-Santos & Osório, 2015).
Similarly, an online study (n> 7,300, ages 18–75+ years) employ-
ing the Penn Emotion Recognition Test with happy, sad, angry,
and fearful faces showed that women more accurately identified
emotions across the lifespan (d= 0.41) (Sasson et al., 2010).
Importantly, women were particularly proficient at detecting
negative emotions, though the specific negative emotions were
not always consistent across studies and the effect sizes were
small. In a large meta-analysis (n> 79,000), which encompassed
several of the prior meta-analyses with children through adults
in nations from Africa, East and Southeast Asia, Europe, North
and South America, and including New Guinea, Taiwan, and
Tibet, an overall female advantage was found in accurate recogni-
tion of emotional reactions to threat (d= 0.24) and of positive
emotions (d= 0.19) (Thompson & Voyer, 2014). For specific
emotions, the effect sizes were highest for anger (d= 0.25), sad-
ness (d= 0.24), and fear (d= 0.22), then slightly lower for happi-
ness (d= 0.18), disgust (d= 0.17), and surprise (d= 0.15),
indicating that females were more accurate than males at all
ages in decoding emotional signals of threat from non-verbal
expressions.
In an Emotion Recognition Test (n> 42,000, ages 11–78 years)
conducted in seven South American nations, plus Mexico,
Austria, Germany, Spain, Switzerland, and the United States,
females were more accurate than males at identifying emotions
(d= 0.22) (Merten, 2005). For specific emotions however, the sex
difference was significant only for anger, fear, and sadness (not
for disgust, joy, or surprise). In three online studies (n> 1,900) in
which subjects rated static facial and dynamic bodily emotions in
less than one second, women recognized disgust and sadness signif-
icantly more accurately than men did, but not anger, fear, or hap-
piness (Connolly, Lefevre, Young, & Lewis, 2019).
McClure (2000)’s meta-analysis of 58 studies of facial emotion
processing in infancy through adolescence likewise demonstrated
that girls were more accurate than boys at identifying emotions.
The effect size was smaller in older children and adolescents
(d= 0.18) than in infants (d= 0.70) however, which may be attrib-
utable to the earlier maturity of infant females than males
(McClure, 2000).
Thus overall we found that females are reported to accurately
identify others’emotions more than males.
3.4. Avoidance of confrontation
SAT would predict that females are more likely than males to
avoid confrontations and facilitate positive interactions. We
found two forms of confrontation with systematic evidence: direct
competition and face-to-face aggression.
Evidence indicates that direct competition and aggression are
less common in females than males with moderate to large effect
sizes. Direct competition has been systematically examined both
in economic games and sports. A standardized economic game
was created in which individuals chose to either compete against
others or work alone with equal expected payoffs (Niederle &
Vesterlund, 2007). In WEIRD and non-WEIRD societies, across
tasks, group size, and sex of opponents, two reviews concluded
that girls and women were less likely than boys and men to com-
pete against others (Klege, Visser, Barron, & Clarke, 2021; Sutter,
Zoller, & Glatzle-Rutzler, 2019). Based on Klege et al. (2021), we
calculated effect sizes for 33 studies with adults (d= 0.43) and 12
studies with children (d= 0.55).
Similar evidence comes from sports. Throughout known his-
tory, cross-culturally women have participated less than men in
competitive sports (Craig, 2002; Leibs, 2004). In a geographically
and culturally diverse sample of 50 societies, of 248 sports docu-
mented, males participated in 95% of the sports and females in
20%, whereas no sex differences existed in participation in amuse-
ments (Deaner & Smith, 2013). In the detailed American Time
Use Survey (2003–2010) of activities in the past 24 hours (n>
112,000), 0.64% of females and 2.69% of males (d=−0.92) partic-
ipated in team sports, and 1.29% of females and 4.45% of males
participated in 1:1 sports (d=−0.95), whereas no sex differences
occurred in exercise (Deaner et al., 2012). Whether in the context
of sports or simply informal interactions, ethnographic evidence
Benenson et al.: Self-protection as an adaptive female strategy 11
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
from Africa, Canada, Europeans, Native Americans, and in
Oceania also described the less competitive and conflictual rela-
tionships of girls and women compared with boys and men
(Locke, 2011).
Similar to findings on sex differences in direct competition,
females were found to engage in less verbal (d=−0.30) and phys-
ical (d=−0.59) confrontation than males (Archer, 2019), with
moderate effect sizes. Although most studies came from Asia,
Europe, and North America, ethnographic reports provided the
same conclusion. Despite large cultural variation, females engaged
in less frequent and severe direct aggression than males did (Fry,
1998; Locke, 2011). The sex difference in direct aggression
occurred across diverse cultures by age 2 years and continued
through adolescence (Maccoby & Jacklin, 1974). In non-human
primates as well, females typically engaged in less intense physical
aggression than males (Sabbi et al., 2021; Smuts, 1987).
Thus evidence from smiling, politeness, emotion identifica-
tion, and avoidance of direct confrontation indicated that females
invested more than males in reducing social conflicts and protect-
ing social bonds. This result is consistent with the finding from 70
countries with student and adult samples (n> 75,000) that
women evaluated the “preservation and enhancement of the wel-
fare of people with whom one is in frequent personal contact”as
more important than men did (d= 0.19–0.36) (Schwartz & Rubel,
2005).
4. Personality style as a response to threat
Neuroticism consists of a wide range of negative behaviors,
moods, emotions, and thoughts. One component of neuroticism,
focused on worry and feelings of vulnerability, has been associated
with reduced morbidity and mortality (Weiss & Deary, 2020).
Because worry and feeling vulnerable are consistent with promot-
ing self-protective behaviors toward threats, we interpreted SAT as
predicting that females should report higher neuroticism than
males.
The conclusion from four large cross-cultural studies is that
beginning in adolescence, women exhibit higher neuroticism
than men. First, in a study of university students (n> 17,500),
neuroticism was defined as worrying, tension, nervousness,
depression/blue, moodiness, uncalm in tense situations, easily
upset, and not relaxed/handling stress poorly. In 49 of 55 coun-
tries, women reported more neuroticism than men did, whereas
in no country did men report higher neuroticism than women
(d= 0.40). Figure 7 displays effect sizes for sex differences in person-
ality styles from world regions with neuroticism showing small to
moderate sex differences (Schmitt, Realo, Voracek, & Allik, 2008).
Second, in an online study with individuals primarily from
Australia, Canada, Ireland, New Zealand, and the United States
(n> 1.2 million, ages 10–65 years, 70% Caucasian, 8% Asian,
6% African, 6% Hispanic), neuroticism was defined by worrying,
not remaining calm in tense situations, being depressed/blue, and
being moody (Soto, John, Gosling, & Potter, 2011). Overall neu-
roticism, and sub-clinical levels of anxiety and depression, dif-
fered by sex with females’rates increasing in early adolescence
and remaining high during their peak reproductive years as dis-
played in Figure 8.
Third, a study of US adults (n> 320,000) defined neuroticism as
being anxious, angry, depressed, self-conscious, immoderate, and
vulnerable. As before, women, particularly during their reproduc-
tive years, described themselves as more neurotic than men (d=
0.40) with the anxiety (d= 0.56) and vulnerability (d= 0.54) scores
yielding the greatest sex differences (Kajonius & Johnson, 2018).
Finally, in a classic study of personality in 24 highly diverse
countries with university students and adults, women rated them-
selves as more neurotic than men: more vulnerable (d= 0.28–
0.44), anxious (d= 0.32–0.43), self-conscious (d=0.22–0.30),
depressed (d= 0.17–0.24), impulsive (d= 0.11–0.23), and angry/
hostile (d=0.09–0.19), although sex differences in angry/hostile
were not always significant (Costa, Terracciano, & McCrae, 2001).
In childhood, as depicted above, sex differences in neuroticism
began after age 10 years. Facets of neuroticism, particularly anxiety,
however, demonstrated sex differences even earlier (Soto et al., 2011).
In summary, beginning in adolescence females consistently
report higher neuroticism than males, with small to moderate
effect sizes. The greater neuroticism of post-pubertal females con-
forms to the prediction from SAT, suggesting that neuroticism
functions to protect females more effectively than males from a
diversity of threats.
5. Emotions: immediate reactions to threat
Emotional reactions to threat constitute critical signals that
promote staying alive (Darwin, 1872; Ekman & Oster, 1979;
Lazarus, 1991). Six basic emotions have been identified because
they appear across diverse cultures, occur in other primates, and
emerge in childhood (Ekman & Cordaro, 2011). Four of these
(fear, disgust, sadness, and anger) are considered responses to
threat, whereas two (joy and surprise) are not. Each basic emotion
arising in response to a threat is believed to produce a unique
aversive signal that promotes a defensive action aimed at remov-
ing or avoiding the threat.
Assuming that emotional responses to threat promote survival,
SAT would predict that females should experience these emotions
more than males. We therefore tested the hypothesis that females
experience more fear, disgust, sadness, and anger than males.
5.1. Fear
Fear enhances survival by motivating an individual to withdraw
from potentially life-threatening danger (Ekman & Cordaro, 2011;
Lazarus, 1991). Campbell (1999) predicated SAT on female’sgreater
fear of physical aggression, while our extension of SAT predicts that
females would exhibit greater fear than males to any threat.
Cross-cultural studies confirm that women tend to display
greater fear than men. Archer’s(2019) review reported greater
fearfulness for adult females than males with small to large effect
sizes (d=0.07–1.16). Additionally, when university students (n=
5,000) from 11 countries were asked to rate the fearfulness of 52
stimuli organized into social, agoraphobic, bodily, and animal cat-
egories, women in every nation reported greater fearfulness to
every category (d= 0.02–0.90) (Arrindell et al., 2004). Further,
in 1975–1980 when university students from 28 diverse countries
were asked whether either sex was better described by various
adjectives, women were characterized as more fearful than men
in every country (Williams & Best, 1990).
In the International College Student Data (ICSD) survey (n>
6,000, 39 countries), students reported how frequently and
intensely they experienced different emotions. Women described
more frequent and intense fear than men (d= 0.31) (Lucas &
Gohm, 2000). In two studies, one with an Australian sample of
students, kin, and friends (n> 2,100), and a second with an inter-
national sample of students from 41 countries (n> 6,500), women
12 Benenson et al.: Self-protection as an adaptive female strategy
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reported more frequent fear in the past month in Australia (d=
0.14) and in the international sample (d= 0.17) and more intense
feelings of fear in the international sample (d= 0.26) (Brebner,
2003).
A small effect has also been found in children. In a cross-
cultural meta-analysis (n>4,500, 3 months–13 years), girls
displayed greater fear than boys (d= 0.12) (Else-Quest et al.,
2006).
Figure 7. Magnitudes of sex differences in neuroticism by world region based on the International Sexuality Description Project. © Reprinted with permission of the
American Psychological Association.
Figure 8. Sex differences in neuroticism by age in a large English-speaking sample. © Reprinted with permission of the American Psychological Association.
Benenson et al.: Self-protection as an adaptive female strategy 13
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
5.2. Disgust
Like fear, disgust is believed to enhance survival by producing
withdrawal from potentially life-threatening danger (Ekman &
Cordaro, 2011; Lazarus, 1991). Classically, disgust arises in
response to illness-causing objects, such as feces, vomit, mucous,
signs of severe illness, rotting flesh, and other potentially contam-
inating stimuli. Additional, less well-known forms of disgust
include sexual, animal, and moral disgust. Experiencing greater
disgust or revulsion is directly linked with higher germ avoidance
(Hartmann & Siegrist, 2018), immediately increased immune acti-
vation (Schaller, Miller, Gervais, Yager, & Chen, 2010; Stevenson
et al., 2012), and disease avoidance (Curtis, Aunger, & Rabie,
2004; Oaten, Stevenson, & Case, 2009). Since disgust acts as a
mechanism for self-protection, SAT would predict that females
would experience greater disgust than males.
We found that across varied disgust-producing stimuli, females
experienced more disgust than males, with small to large effect
sizes. In an online cross-cultural study (n> 390,000, 67 countries),
women were more distressed than men about lack of physical/
spiritual purity and contamination (Atari, Lai, & Dehghani,
2020). Likewise, on the BBC science website (n> 39,000), children
and adults evaluated which of two paired images evoked more
disgust. Across ages and continents, females were more likely
than males to rate the image designed to appear as if it could
transmit disease as more disgusting than its disease-free twin
(Curtis et al., 2004). In another online study (n> 6,100, ages
20–69 years, 10 nations, 5 continents), researchers examined dis-
gust ratings for animal flesh, poor hygiene, human contamination,
mold, decaying fruits, fish, decaying vegetables, and living con-
taminants (Egolf, Hartmann, & Siegrist, 2019). Across countries
women’s disgust ratings were greater than men’s(d= 0.12–
0.37). Similarly, participants from Canada, England, and the
United States (n> 2,500, mean age 28 years) evaluated degree of
disgust toward five targets. Women provided higher ratings
than men for animal disgust (d= 0.82), sex disgust (d= 0.70),
hygiene disgust (d= 0.48), food disgust (d= 0.44), and lesion dis-
gust (d= 0.31) (Curtis & de Barra, 2018). Sexual stimuli produced
some of the largest sex differences. Women experienced greater
disgust than men to sexual stimuli (d= 0.60–1.54) (Al-Shawaf,
Lewis, & Buss, 2018).
Sex differences in disgust appeared in childhood. As described
in the large paired comparison study which began at age 7 years,
even the youngest girls exhibited greater disgust than boys (Curtis
et al., 2004).
5.3. Sadness
Sadness is believed to result from the loss of someone or some-
thing important to one’s life (Ekman & Cordaro, 2011; Lazarus,
1991). Attachment theory posits that sadness or grief represents
separation distress from a support figure (parent, spouse, ally)
or from someone with close genetic ties (child, twin) (Archer,
2008; Bowlby, 1980). Loss of a relationship partner can threaten
the bereaved’s survival (Holt-Lunstad et al., 2015) or reproductive
success (Archer, 2008) and often leads to withdrawal. Unlike with
fear and disgust however, with sadness the loss often has already
occurred, and withdrawal is gradual rather than sudden.
Withdrawal is believed to protect the bereft individual who likely
has lost a current or future ally, and to help elicit support from
others (Lomas, 2018). On the assumption that sadness functions
to reduce the impact of a threatening factor (the loss of a relation-
ship partner), SAT would predict that females would experience
greater sadness than males.
Based on self-reports, females were found to exhibit more sad-
ness than males, with small effect sizes. In the IAPS, standardized
photographs depicting illness generated more sadness in women
than men (Bradley et al., 2001). In the 39 nation ICSD survey,
women reported more frequent and intense sadness than men
did (d= 0.26) (Lucas & Gohm, 2000). Likewise, women reported
more frequent sadness in Australia (d= 0.17) and the 41 country
international sample (d= 0.16), and more intense feelings of sad-
ness in Australia (d= 0.19) and the international sample (d=
0.28) (Brebner, 2003).
Higher self-reports of sadness could in theory be accounted for
by women’s greater willingness to report emotion. To examine
this possibility, in 1990 researchers interviewed a demographically
representative sample of Americans (n> 2,000, ages 18–90 years)
(Mirowsky & Ross, 1995). When asked the number of days in the
prior week they felt sad, women reported more days of sadness
than men. Then, participants were asked how much they hide
their emotions. At every level of emotional reserve, women
reported experiencing greater sadness than men, strongly suggest-
ing that the sex difference in reported sadness was not due to a
reporting bias.
Limited evidence suggests girls are sadder by adolescence. In a
demographically representative American sample (n> 21,000,
ages 14–18 years), girls felt sadder than boys (Moeller, Brackett,
Ivcevic, & White, 2020). Likewise, when Swedish adolescents
(n> 1,000, ages 16–18 years) in 49 classrooms were asked how
frequently they experienced sadness, 35% of the girls versus 8%
of the boys reported feeling sad either “fairly often”or “very
often”(OR = 6.19) (Wiklund, Malmgren-Olsson, Öhman,
Bergström, & Fjellman-Wiklund, 2012). In childhood, sex differ-
ences in sadness may not exist or are negligible. In a meta-analysis
(n> 2,300), in 11 of 16 studies in early and middle childhood
exhibited girls greater sadness than boys, but the sex difference
was not significant and negligible in size (d= 0.10) (Else-Quest
et al., 2006).
Evidence also indicated that females cry (weep) more than
males, with moderate to large effect sizes. Crying is often associ-
ated with sadness, although it can also serve as a release from
emotion and as a means of soliciting support (Rottenberg,
Bylsma, & Vingerhoets, 2008; Vingerhoets & Scheirs, 2000).
In the International Study of Adult Crying (ISAC) (n> 5,500)
conducted in 37 nations across six continents, university students
were asked how easily and how frequently they had cried in the
past month (Van Hemert, van de Vijver, & Vingerhoets, 2011).
In every country, women reported crying more easily (d= 1.11)
and more recently (d= 0.94) than men. Another meta-analysis
(15 studies) found that women reported crying more frequently,
intensely, and for longer intervals than men across cultures, includ-
ing Israel, Japan, and the United States (Vingerhoets & Scheirs,
2000). Similarly, across Australia, Croatia, the Netherlands,
Thailand, and the United Kingdom (n>800, ages 18
–40 years),
women reported crying more frequently (d=0.74) and intensely
(d= 0.45) than men (Sharman et al., 2019). Ethnographic
reports from diverse cultures similarly report that the loss of a
relationship partner causes sadness and weeping, and more so in
women than men (Palgi & Abramovitch, 1984). Sex differences
in crying are not reported before adolescence (Vingerhoets &
Scheirs, 2000).
14 Benenson et al.: Self-protection as an adaptive female strategy
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5.4. Anger
Anger occurs after a personal goal has been obstructed, often by a
specific perpetrator who purposefully wishes to harm a victim
and/or her/his associates (Ekman & Cordaro, 2011; Lazarus,
1991). Unlike fear, disgust, and sadness however, anger activates
approach, not withdrawal. A further contrast is that although
anger-motivated responses can reduce a threat through avoidance,
they can also increase the risk of being injured through approach-
ing a perpetrator (Sell, Tooby, & Cosmides, 2009). This means
that whether anger functions as self-protection will vary with
the context. Anger should be more self-protective if it enhances
avoidance of a perpetrator, but less self-protective if it motivates
close engagement or cycles of retaliation. Experiencing anger
without approaching the perpetrator however should highlight
the danger of future interactions with specific perpetrators,
thereby enhancing survival.
SAT therefore would predict that females would feel angrier
than males toward perpetrators, though only when the approach
was suppressed. Even though the prototype of an angry person is
a man (Kring, 2000) most likely because larger individuals face
lower likelihood and costs of retaliation (Sell et al., 2009), we
tested the hypothesis that females feel angrier than males.
Evidence suggested at most a negligible effect size indicating
females experienced more anger than males (Archer, 2004;
Kring, 2000). However, no studies distinguished simple anger
from anger tied to aggression. A meta-analysis of 11 countries
found a non-significant effect for females to feel angrier than
males (d= 0.04) (Archer, 2004). In the ICSD study, women
reported more frequent anger than men (d= 0.08) (Lucas &
Gohm, 2000). Likewise, in Brebner’s(2003) Australian and interna-
tional samples, women reported experiencing anger more frequently
thanmendidbothinAustralia(d= 0.06) and the international
sample (d= 0.05). Women also reported greater intensity of anger
in the international sample (d= 0.14). In Mirowsky and Ross
(1995) American study, anger was defined as “feeling annoyed
with things or people,”“feeling angry,”and “yelling at someone.”
Women reported feeling angrier than men, and “yelling at some-
one”more than men did. Sex differences in experiencing anger
have not been found in children (Potegal & Archer, 2004).
In conclusion, evidence supported the hypothesis that females
experienced more fear, disgust, and sadness than males did. Results
did not support an overall sex difference in anger but anger could
not be separated from approaching a perpetrator. When a sex differ-
ence did arise however, women experienced more anger than men.
6. Clinical conditions: extreme self-protective reactions to
threat
Some clinical conditions are believed to be non-adaptive exagger-
ations of normal adaptive reactions to stress (Del Giudice, 2018;
Nesse, 2005). If self-protectiveness is an adaptive female strategy,
then clinical conditions constituting extreme self-protectiveness to
threats should be more prevalent in females than males. We there-
fore tested whether extreme forms of physical, social, emotional,
and generalized reactions to threat occur more frequently in
women than men.
6.1. Autoimmune diseases
As we reviewed above, non-pregnant women tend to exhibit stron-
ger immune responses than men including enhanced Th2 reactions.
Extrapolating from this result, we reasoned that more females than
males would develop extreme immunoenhancing conditions. We
therefore searched the literature to test the hypothesis that more
females than males develop extreme immune reactions.
The prediction was supported by evidence that globally, women
are more likely than men to develop systemic autoimmune diseases
(AD) which are linked to proinflammatory responses with moderate
effect sizes (Ji, Sundquist, & Sundquist, 2016; Moroni, Bianchi, &
Lleo, 2012;Purnamawatietal.,2018) and diminish in severity dur-
ing pregnancy (Abu-Raya et al., 2020). Of 81 ADs identified world-
wide, 47 afflict females more than males, 22 are more common in
males, and 9 exhibit no sex difference (Hayter & Cook, 2012).
Despite large cultural differences, overall 6.4% of females and
2.7% of males develop an AD (OR = 2.46) with onset most common
between 20 and 29 years. The more prevalent an AD, the higher the
proportion of females who develop it, with women comprising 78%
of those with ADs (Hayter & Cook, 2012). Whereas many female-
preponderant ADs are believed due to enhanced Th2 responses, in
male-preponderant ADs, Th1 reactions often are stronger
(Fairweather, Frisancho-Kiss, & Rose, 2008). Precipitating factors
for all ADs include infections or other types of diseases or trauma
(Nielsen, Kragstrup, Deleuran, & Benros, 2016). Results therefore
are consistent with a female adaptation that promotes immunoen-
hancing reactions to physical threat.
6.2. Pain disorders
Evidence reviewed above demonstrated that females experience
more ordinary pain than males. According to the idea that clinical
conditions are non-adaptive extensions of well-adapted responses,
extreme pain reactions should be found more often in females
than in males.
We found two examples for which cross-cultural evidence is
available, migraine headaches and fibromyalgia (FM), both of
which were experienced by more females than males. The
Global Burden of Diseases report finds that despite large national
variations, worldwide 18.9% of women and 9.8% of men experi-
enced migraine headaches (OR = 2.15) with women ages 15–49
years most affected (Stovner et al., 2018). The most common pre-
cipitating factor was external stress, including odors, foods,
weather, pain to the neck or head, or emotional trauma
(Peroutka, 2014; Woldeamanuel & Cowan, 2017).
FM consists of chronic, severe, widespread pain in at least 11
of 18 points in the joints, muscles, and spine. Worldwide, 4.2%
of females and 1.4% of males (OR = 3.09) developed FM
(Queiroz, 2013). Onset of FM typically followed a stressor, such
as an accident, surgery, infection, or emotional trauma, and was
accompanied by sleep disturbance, fatigue, memory, and concen-
tration problems, along with depression and anxiety
(Galvez-Sánchez, Duschek, & del Paso, 2019; Häuser, Thieme,
& Turk, 2010). Prevalence ratios of migraine and FM showing
moderate effect sizes were consistent with the hypothesis that a
female adaptation exists for heightened experience of pain.
6.3. Sleep disorders
Prior evidence showed that females experienced more nighttime
awakenings than males, which is plausibly an adaptive response.
More extreme, non-adaptive nighttime awakenings were therefore
also expected to occur more often in females than in males. We
therefore tested whether more females than males developed con-
ditions with severe nighttime awakening.
Benenson et al.: Self-protection as an adaptive female strategy 15
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In line with this prediction, we found that more women than
men experienced severe sleep disturbances with small to moderate
effect sizes. Although no sharp distinction separates nighttime
awakenings from a severe sleep disorder (Suh et al., 2018), analy-
ses of major DSM-V clinical conditions showed a female:male
prevalence ratio of 1.4 for insomnia disorder and 1.5–2 for restless
leg syndrome, which disrupts sleep, as well as a higher female
prevalence for nightmare disorder (Hartung & Lefler, 2019).
Ameta-analysis(n> 18,500) further confirmed a female preponder-
ance for restless leg syndrome (OR = 1.63–2.22) (Ohayon & Roth,
2002). Additionally, a detailed study in Hong Kong (n> 8,500)
found women were more likely than men to experience nightmares
⩾3 times/week (OR = 2.10) (Li, Zhang, Li, & Wing, 2010).
Furthermore, major sleep disruptions including day-night
reversals were associated with clinical conditions with a female
preponderance (Lashley, 2003). These included responses to
infections, many autoimmune conditions (systemic lupus
erythematosus, multiple sclerosis, rheumatoid arthritis), pain-
related disorders (migraine, FM), and as described below, anxiety
disorders, major depression, post-traumatic stress disorder,
and chronic fatigue syndrome. Prevalence ratios of severe sleep
disruption were consistent with the thesis that because a female
adaptation exists for being especially attuned to nighttime threats,
females were also vulnerable to having extreme responses that are
likely maladaptive.
6.4. Separation disorder
We have presented evidence that females were more likely than
males to avoid social confrontations and to become more dis-
tressed about relationship partners’well-being. A more extreme
version of this response would consist of becoming extremely dis-
tressed about the loss of relationship partners. We therefore tested
whether more females than males develop conditions character-
ized by excessive concern for the maintenance of relationships.
We found one condition with cross-cultural evidence that clearly
fit this criterion: separation anxiety disorder. Separation anxiety
disorder includes severe distress at being away from an attach-
ment figure along with persistent worry about negative events
befalling attachment figures.
Examining 18 DSM-IV mental disorders (n> 72,000, across
Africa, the Americas, Asia, Europe, the Middle East, and the
Pacific), the WHO World Mental Health Survey (WMHS) study
found that lifetime prevalence of separation anxiety disorder
was more common in females than males with a small effect
size (OR = 1.6), whereas the reverse was true for antisocial disor-
ders (Seedat et al., 2009). Similarly, in analyses of the DSM-V cat-
egories, separation anxiety disorder was more common in females
than males, while males suffered more from antisocial disorders
(Hartung & Lefler, 2019; Holthausen & Habel, 2018; Shear, Jin,
Ruscio, Walters, & Kessler, 2006). A demographically representa-
tive survey in the United States (n> 14,000) likewise showed that
by the end of early childhood and throughout life females were
more likely than males to have experienced separation anxiety dis-
order (OR = 2.2) (Shear et al., 2006). Reported rates of separation
disorder are thus consistent with a heightened female adaptation
for maintaining relationships.
6.5. Anxiety disorders
Evidence reviewed above demonstrated that females of all ages
were more likely than males to experience fear in response to
threats. More persistent and intense fear reactions would accord-
ingly be expected to develop in females than males. We therefore
tested whether more females than males developed conditions
characterized by severe fear.
Anxiety disorders are specific or generalized worries and fears
about potential threats often accompanied by unpleasant physical
sensations, including increased heart rate and shaking. The world-
wide WHO WMHS study showed a higher prevalence for females
than males of anxiety disorders with small effect sizes, including
panic disorder (OR: 1.9), generalized anxiety disorder (OR: 1.7),
agoraphobia (OR: 2.0), social phobia (OR: 1.3), specific phobia
(OR: 2.0), separation anxiety disorder (OR: 1.6) as mentioned,
and any anxiety disorder (OR: 1.7) (Seedat et al., 2009). Other
estimates of the female:male ratio of global prevalence of anxiety
disorders were 1.9 (Remes, Brayne, Van Der Linde, & Lafortune,
2016) with the DSM-V analysis finding a ratio of 2:1 (Hartung &
Lefler, 2019). Thus, anxiety disorders conform to the hypothesis
that they represent exaggerated versions of responses that would
be adaptive if produced at an appropriate level.
6.6. Major depression and suicide attempts
Earlier we showed evidence that females were more likely than
males to experience sadness. Extrapolating from this produces
the prediction that more females than males should develop an
extreme form of sadness: depression. We tested this hypothesis.
Major depression consists of an array of uncomfortable emo-
tional and physical symptoms including sadness, feelings of worth-
lessness, reductions in activity and energy levels, changes in appetite
and sleep, and difficulty thinking. In 80% of cases, depression is pre-
cipitated by stress (LeMoult, 2020). A meta-analysis of sex differ-
ences in major depression across six continents (n> 1.7 million,
ages 12–70+ years) showed a higher female prevalence with a mod-
erate effect size (OR = 1.95) (Salk, Hyde, & Abramson, 2017). The
DSM-V analysis reported depression to be 1.5–3 times more com-
mon in women than men (Hartung & Lefler, 2019).
Major depression likely plays a role in suicide attempts. Suicide
attempts however may be not only an exaggeration of depression,
but also an adaptive request for help across diverse societies
(Syme, Garfield, & Hagen, 2016). Although cross-culturally
women were less likely than men to commit suicide (Alothman
& Fogarty, 2020; WHO, 2014b), women were more likely than
men to attempt suicide, beginning in early adolescence
(Freeman et al., 2017; Lenz et al., 2019; WHO, 2014b).
Maximal rates of non-fatal self-injuries for females occurred
between 10 and 24 years (OR =1.72). Females were still more
likely than males to attempt suicide between 25 and 44 years
(OR = 1.29), but the sex difference became negligible at older
ages (Nock et al., 2008). A meta-analysis of suicide attempts by
12–26-year-olds further found that in 23 of 24 studies girls
were more likely than boys to attempt suicide (OR = 1.96)
(Miranda-Mendizabal et al., 2019). Effect sizes range from small
to moderate. The higher rates of depression and lower success
of female suicide attempts can be interpreted as females being
more invested in self-protection, in line with SAT.
6.7. Psychiatric disorders incorporating disgust
We found previously that females were more likely than males to
experience disgust in response to potentially contaminating
stimuli. We therefore tested the idea that more extreme forms
of disgust would also be more common in females than males.
16 Benenson et al.: Self-protection as an adaptive female strategy
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We found that disgust is integral to three psychiatric illnesses:
animal phobias, contamination-related obsessive–compulsive dis-
orders with continual washing (OCD), and blood-injection-injury
(BII) phobia which can include fainting. All three of these ill-
nesses were more common in women than men (Arrindell,
Mulkens, Kok, & Vollenbroek, 1999;Davey,2011; Mathis et al.,
2011; Olatunji, Cisler, McKay, & Phillips, 2010; Wani & Ara,
2014). Disgust has also been associated with other serious psychi-
atric problems that are more prevalent in women than men,
including eating disorders, agoraphobia, and female sexual dys-
function (Hartung & Lefler, 2019). In all cases, specific threats
were the focus. In contrast, most hypersexual-related psychiatric
illnesses were more frequent in men than women. Thus, evidence
supported the idea that extreme forms of disgust were experienced
by more females than males.
6.8. Threat-induced conditions
Given evidence that females reacted more self-protectively than
males to threats, it would be expected that conditions having well-
established associations with threat should develop in more
females than males. We therefore searched for conditions in
which identifiable threats constituted clear precipitating factors,
to test whether more females than males developed these condi-
tions. We found two conditions known to be caused by stress:
post-traumatic stress disorder (PTSD) and chronic fatigue
syndrome also known as myalgic encephalomyelitis (CFS/ME).
Both PTSD and CFS/ME demonstrate a female preponderance.
PTSD follows trauma and consists of intense, long-lasting
emotional and physical symptoms, typically flashbacks, hypervig-
ilance, and nightmares, as well as major depression, anxiety, and
sleep disorders. In a WHO WMHS study in 15 diverse societies
(n> 72,900), females experienced PTSD more than males
(OR = 2.6) (Seedat et al., 2009).
Sex differences in experience of PTSD however must control
for the nature of the precipitating stimulus. A detailed meta-
analysis (290 studies) of types of trauma producing PTSD in pri-
marily WEIRD societies showed that for every type of trauma
except childhood sexual abuse, more females than males devel-
oped PTSD (OR = 1.98) (Tolin & Foa, 2006). Further detail
came from a Nordic study (n> 5,200) in which approximately
twice as many women (25.6%) as men (13.2%) were categorized
as having PTSD (Ditlevsen & Elklit, 2012). Using a continuous
measure of PTSD, females experienced stronger PTSD than
males with effect sizes varying from small to large based on
type of trauma: disasters and accidents (d= 0.84), loss (d=
0.47), non-malignant disease (d= 0.47), chronic disease (d=
0.39), violence (d= 0.27), and overall (d= 0.60).
While the female preponderance of PTSD could be due to
more females than males experiencing severe trauma, current evi-
dence disputed this. In the meta-analysis in WEIRD countries,
fewer females than males confronted severe traumas (OR = 0.77)
(Tolin & Foa, 2006). Likewise, globally, females were less likely
than males to die from fatal injuries (WHO, 2014a) or become
disabled due to injuries (Haagsma et al., 2016).
CFS/ME is a debilitating, often life-long condition. Along with
extreme exhaustion and weakness, the most common symptoms
include immune activation (flu-like symptoms), intense pain
(often migraines), severe sleep disturbance, depression or anxiety,
concentration problems, and adverse reactions to chemicals (Chu,
Valencia, Garvert, & Montoya, 2019; Friedman, 2019; Natelson,
2019). Based on a review of 13 Asian, Australian, North and
South American studies, despite varying national prevalence
rates, after puberty women were 3–4 times more likely than
men to develop CFS/ME (Son, 2012) with a large effect size in
an American study (OR = 4.51) (Reyes et al., 2003). Onset typi-
cally occurred between ages 20 and 45 years following a specific
threat: an infective illness (64% of cases), a major aversive life
event (emotional stressor in the family or at work in 39% of
cases), and a reaction to environmental toxins such as vaccines
(20% of cases), with multiple precipitating stressors for some indi-
viduals. CFS/ME is not believed to be a disease in the typical
sense, but rather a systemic reaction to stress (Cortes Rivera,
Mastronardi, Silva-Aldana, Arcos-Burgos, & Lidbury, 2019).
Prevalence rates of both PTSD and CFS/ME thus supported the
prediction that more females than males exhibited extreme self-
protective reactions to threats.
In conclusion, eight types of threat-related clinical condition,
although maladaptive, may reasonably be interpreted as extreme
self-protective reactions, and were more prevalent in females
than males.
7. Discussion
7.1. Sex differences in self-protective responses
Our goal was to evaluate whether Campbell’s(1999) SAT applied
not merely to physical aggression but more generally to all threats.
By searching the literature for cross-cultural evidence with large
samples, we tested the hypothesis that females demonstrate
more self-protective reactions than males to major threats. We
found that females exhibited stronger self-protective reactions
than males to important biological and social threats; a personal-
ity style more geared to threats; stronger emotional responses to
threat; and more threat-related clinical conditions suggestive of
heightened self-protectiveness. That females expressed more
effective mechanisms for self-protection is consistent with
females’lower mortality and greater investment in childcare com-
pared with males. Table 2 summarizes our major findings. As our
hypothesis would predict, the magnitudes of sex differences in
self-protective reactions were largest for the most potent threats
to life –including heightened antibody production, reduced
endurance of pain, and greater avoidance of direct competition,
with fear, disgust, and crying sometimes also producing large
effect sizes.
Our test of Campbell’s extended SAT is limited by our inability
to examine every conceivable kind of threat, and by the incom-
plete availability of cross-cultural data. Nevertheless, we found
evidence from many large samples and diverse cultures.
Strikingly, despite intense searching, we failed to find large studies
or meta-analyses that showed sex differences in the opposite
direction to those expected from SAT. We conclude that the ten-
dency for females to show more self-protective physiology, social
interactions, personality styles, emotional reactions, and threat-
related clinical conditions than males provides a strong first test
for the extension of Campbell’sSAT.
Many additional potential examples of greater female self-
protectiveness occur in important areas that we excluded due to
limited cross-cultural evidence. As examples, females more than
males exhibit a lower threshold for detecting many sensory stim-
uli (Velle, 1987); remain closer to home (Ecuyer-Dab & Robert,
2004); overestimate the speed of incoming stimuli, discuss threats
and vulnerabilities more frequently, find punishment more aver-
sive, demonstrate higher effortful control, and experience deeper
Benenson et al.: Self-protection as an adaptive female strategy 17
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empathy (Archer, 2019); express greater concern over friend’s
(Hall, 2011) and romantic partner’s (Carpenter, 2012) loyalty;
and seek more frequent help (Möller-Leimkühler, 2002; Tamres,
Janicki, & Helgeson, 2002; Whiting & Whiting, 1975).
Developmental evidence generally supported the prediction
that females would exhibit greater self-protective reactions than
males throughout life, but that the magnitude of the sex difference
would increase following puberty when females can reproduce.
Sex differences in immune functioning, pain, and nighttime
awakenings appeared in childhood, but increased post-pubertally.
Sex differences in politeness, emotional identification, and avoid-
ance of confrontations emerged by early childhood, but in smiling
only after puberty. Sex differences in neuroticism arose only after
puberty, but girls displayed some components of neuroticism
more than boys pre-pubertally. Girls experienced greater fear
and disgust than boys pre-pubertally, but not sadness, for which
the sex difference only clearly arose post-pubertally.
We did not systematically examine sex differences in children’s
clinical conditions due to lack of cross-cultural evidence.
However, sex differences in some conditions, such as anxiety
(Rescorla et al., 2007) and depression (Salk et al., 2017), emerge
only after puberty, whereas in others, such as immune function-
ing, shifts occur from childhood to puberty (Klein & Flanagan,
2016).
7.2. Complexities in interpreting sex differences
That numerous sex differences conform to SAT is consistent with
the thesis that self-protective reactions constitute a series of
evolved female adaptations. If sex differences are to be fully
understood however, additional factors must be included.
First, sex/gender is a multidimensional construct resulting
from the continuing interplay between biological and environ-
mental factors (Berenbaum & Beltz, 2021; Eliot, 2009; Fausto-
Sterling, 2019; Hyde et al., 2019). Further, some of its important
components and related constructs, including epigenetic
configurations, hormonal balances, reproductive capacity, gender
identity, gender roles, and sexuality, often fluctuate over the
Table 2 Threats, self-protective responses, extreme protective reactions, and fatal conditions with estimates of adult female:male odds ratios (OR)*.
Threat Protective response Extreme protective reaction
Fatal conditions
overall mortality
(0.66)
I
External pathogens and internal
pathologies
Antibody production (4.17)
a
Autoimmune disease
(2.46)
aa
CVD (0.70)
II
Cancer (0.45–0.68)
III
COVID-19 (1.59)
IV
Non-pharmacological (1.49)
b
and pharmacological (0.89)
b
Preventive behaviors to pandemics
Bodily damage Adverse reactions to pictured environmental
threats (1.92–4.27)
c
Lower threshold for pain (2.52)
d
Shorter endurance of pain (8.35)
d
Migraine (2.15)
bb
Fibromyalgia (3.09)
cc
Accidental injuries
V
Road traffic (0.37)
Drowning (0.43)
Poisoning (0.57)
Fire-related (0.95)
Nighttime threats Sleep disturbances
(1.06–1.46)
e
Nightmares
(0.94–1.60)
f
Insomnia disorders
(RR = 1.41)
dd
Nightmare disorder (2.10)
ee
Restless leg syndrome
(1.63–2.22)
ff
Obstructive sleep
apnea
VI
(0.27–0.43)
Reduction of social threats and
facilitation of social bonds
Smiling (2.10)
g
Politeness (1.52)
h
Emotion identification
(1.36–2.67)
i
Direct competition (0.19–0.46)
j
Direct aggression (0.34–0.58)
k
Separation anxiety disorder
(1.60)
gg
Major depression (1.95)
hh
Suicide attempt
(1.29–1.96)
ii
Suicide (0.52)
V
Victim of homicide
(0.23)
V
Personality style Neuroticism (2.07)
l
Emotional reactions Fear (1.04–8.20)
m
Disgust (1.24–16.33)
n
Sadness (1.34–1.66)
o
Crying (2.26–7.45)
p
Anger (1.08)
q
PTSD (2.60)
gg
CFS/ME (4.51)
jj
Anxiety disorder (1.70)
gg
*Odds ratios >1 indicate higher prevalence in females than males and <1 indicate higher prevalence in males than females.
a
Yang and Kozloski (2011) antibodies;
b
Moran and Del Valle (2016) pandemic prevention;
c
Bradley et al. (2001), Gong et al. (2018), Gomez et al. (2013), Lang and Bradley (2007), McManis et al.
(2001) adverse reactions to photographs of environmental threat;
d
Riley et al. (1998) pain;
e
Wang et al. (2019) sleep disturbances;
f
Schredl and Reinhard (2011) Hedge’sgnightmares;
g
LaFrance et al. (2003) smiling;
h
Leaper and Robnett (2011) politeness;
i
Connolly et al. (2019), Hall (1978), Hall et al. (2000), Sasson et al. (2010), Thompson and Voyer (2014) emotion
identification;
j
Klege et al. (2021), Deaner and Smith (2013) direct competition;
k
Archer (2019) direct aggression;
l
Kajonius and Johnson (2018), Schmitt et al. (2008) neuroticism;
m
Archer
(2019), Arrindell et al. (2004), Brebner (200) fear;
n
Al-Shawaf et al. (2018), Atari et al. (2020), Curtis and de Barra (2018), Egolf et al. (2019) disgust;
o
Brebner (2003), Lucas and Gohm (2000)
sadness;
p
Sharman et al. (2019), Van Hemert et al. (2011) crying;
q
Archer (2004) anger.
aa
Hayter and Cook (2012) autoimmune disorder;
bb
Stovner et al. (2018) migraine;
cc
Queiroz (2013) fibromyalgia
dd
Zhang and Wing (2006) risk ratio insomnia disorder;
ee
Li et al. (2010) Hong
Kong ⩾3 nightmares/week;
ff
Ohayon and Roth (2002) restless leg syndrome;
gg
Seedat et al. (2009) separation anxiety disorder, PTSD, anxiety disorder;
hh
Salk et al. (2017) major depression;
ii
Nock et al. (2008) non-fatal self-injury; Miranda-Mendizabal et al. (2019);
jj
Reyes et al. (2003) CFS in the USA.
I
GBD (2018) mortality;
II
Mosca et al. (2011) cardiovascular disease;
III
WHO (2021) cancer mortality;
IV
Williamson et al. (2020);
V
WHO (2014a) for deaths from injuries, suicides, and homicides
(we calculated ORs based on graph). We assume being a victim of homicide can be avoided to some extent through self-protective reactions.
VI
Lévy et al. (2015) obstructive sleep apnea.
18 Benenson et al.: Self-protection as an adaptive female strategy
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
lifespan. Thus, menarche and menopause typically produce
diverse changes for human females. Males too undergo transi-
tions. Testosterone diminishes in bachelors who marry and even
further after they father children (Gettler, McDade, Feranil, &
Kuzawa, 2011; Gray, Kahlenberg, Barrett, Lipson, & Ellison,
2002). Because the studies we found do not define sex/gender
and treat it as binary, we cannot specify which characteristics of
sex/gender relate to self-protection. More precise structural, epige-
netic, cellular, hormonal, cultural, social, emotional, cognitive,
and behavioral indices will greatly improve understanding of
the relation between self-protection and sex/gender.
Second, the magnitude of sex differences in self-protectiveness
depends on local threats and safeguards which may differentially
affect females and males. For example, in matrilineal societies
where females receive greater protection from kin (Smuts,
1992), girls and women appear to be as directly competitive as
their male counterparts in economic games (Klege et al., 2021).
Likewise, when women’s rights are protected by laws, the normally
higher rates of men physically battering their female partners
(WHO, 2014a) can disappear (Archer, 2006). In impoverished
societies that provide infants with both nutritional supplementation
and breastmilk, females’immune systems are strengthened more
than males’(Khulan et al., 2012; Osrin et al., 2005). Prevalence
of physical illness itself varies depending on gender identity, role,
and status (Mauvais-Jarvis et al., 2020) and societal kinship struc-
ture (Reynolds et al., 2020). Even sex differences in mortality are
influenced by societal factors, including patients’, physicians’,and
researchers’belief systems (Mauvais-Jarvis et al., 2020); rates of
female infanticide, sexual abuse of and violence against women
(Solotaroff & Pande, 2014;WHO,2014a); and men’swillingness
to seek help (Verbrugge, 1989).
More individual factors also likely regulate the magnitude of
sex differences in self-protective reactions. For example, grand-
mothers typically invest more in daughters’than sons’young chil-
dren, thereby tending to maximize their own fitness (Sear &
Mace, 2008). The extent of a particular grandmother’s investment,
however, should regulate her daughter’s self-protective reactions.
Similarly, although worldwide mothers care for infants (Wood
& Eagly, 2002), a particular family’s norms regarding the exclusiv-
ity of maternal responsibility for childcare likely influences mater-
nal self-protective reactions. As another example, females may have
lower thresholds than males to even perceive physical symptoms,
social conflicts, or other threats, as extrapolation from research
on pain would suggest (Riley et al., 1998). Nevertheless, the degree
to which members of an individual’s social network reward or
punish females’versus males’expressions of vulnerability should
regulate sex differences in even recognizing threats (Jansz, 2000).
Third, more research is necessary to understand the societal
impact of gender equality, measured by women’s participation
and power in public life, on self-protectiveness. Greater gender
equality is associated with even fewer women than men commit-
ting suicide (Alothman & Fogarty, 2020); and increased propor-
tions of women than men expressing concerns about
environmental degradation (Chan et al., 2019), reporting neurot-
icism (Costa et al., 2001; Schmitt et al., 2008), and experiencing
depression (Salk et al., 2017). These somewhat paradoxical find-
ings require further inquiry. Gender equality however is inter-
twined with other ecological and cultural variables (Kaiser,
2019) and may not adequately capture the realities of life of peo-
ple in non-WEIRD societies (Markus, 2021).
Fourth, a large overlap exists between the sexes in many self-
protective reactions as is found in many studies of sex differences
(Eliot, 2009; Hyde et al., 2019; Zell et al., 2015). Consequently, a
particular self-protective response cannot be predicted simply
from knowing an individual’s binary sex. Our evidence merely
demonstrates that there is a population-wide tendency in the
direction predicted by Campbell’s theory.
Distinct self-protective responses, however, frequently co-occur.
Myriad studies report links among somatic, social, neurotic, emo-
tional, and clinical responses (Okur Güney, Sattel, Witthöft, &
Henningsen, 2019;Yunus,2007). This suggests that aggregating
self-protective reactions could more accurately describe the effect
of greater self-protectiveness on females’than males’lives than sim-
ply comparing the sexes on only one self-protective response at a
time. Thus, multivariate statistical techniques could provide a
more qualitative distinction between the sexes (Del Giudice, 2022).
Fifth, many female-prevalent illnesses and clinical conditions
could impede women’s ability to care for their children, thereby
reducing their fitness. An adaptive approach however suggests
that the benefits accrued from women’s greater longevity outweigh
the costs of chronic illness (Del Giudice, 2018; Nesse, 2005).
Overall, considering the diversity of our evidence, the consis-
tency of our findings is striking. Accordingly, we regard sex differ-
ences in self-protective responses as important to investigate not
only for theoretical reasons but also for practical value related
to medical and psychological health (Clayton, 2016; Shansky &
Murphy, 2021).
An analysis of rates of COVID-19 illustrates how sex differ-
ences can vary widely in magnitude without undermining their
significance. Both absolute frequencies and sex differences vary
markedly by ethnicity, age, geographical location, socioeconomic
status, and baseline health status even within the same country, as
depicted in Figure 9 for England (Economist, 2020).
Despite this variation, women are almost always less likely
than men to die within each demographic group. Thus, sex con-
stitutes an important biological variable that can enhance causal
understanding of a phenomenon which varies on many factors
(Clayton, 2018).
Finally, further research is necessary to understand whether
some threats elicit stronger self-protective reactions in men than
women. Examples include male concerns over status and warfare.
Current evidence however indicates no sex differences in the
desire to attain status (Anderson, Hildreth, & Howland, 2015),
even though the sexes may choose different strategies to achieve
it (Benenson & Abadzi, 2020). Whether men are more concerned
than women about imminent military attacks has not been
investigated.
7.3. Complementary explanations
Our findings provide support for self-protective responses as a
female adaptation. Alternative, but potentially compatible, expla-
nations however could also apply.
First, males’higher levels of androgens, larger body size, more
negative social interactions, greater risk-taking, and other sexually
selected characteristics related to mate competition are expected
to partially explain why males exhibit lower self-protectiveness
than females (Dunsworth, 2020; Klein, 2000; Kruger & Nesse,
2006;Zuk,2009). Individual and population variation among
males in their optimal strategies and biological constraints will
therefore contribute to explaining their lower self-protectiveness.
Nevertheless, it is not simply degree of mate competition that
produces sex differences in self-protectiveness. Rather, females
invest in costly self-protective mechanisms, including immune
Benenson et al.: Self-protection as an adaptive female strategy 19
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
functioning and conflict reduction measures, that elevate the
probability of survival. Independent selective pressures on both
male and female traits influence the nature and degree of sex dif-
ferences in self-protectiveness.
Unquestionably, women’s smaller size and muscle mass
enhances their self-protectiveness with men. Nonetheless, sex
differences in size and strength alone cannot explain all
self-protective reactions. For example, in children where sex
differences in size and muscularity are minimal, girls often exhibit
more self-protective reactions than boys, including greater pain to
vaccines (Chambers et al., 1999) or politer language (Leaper &
Smith, 2004; Whiting et al., 1988).
Second, a “trauma hypothesis”might suggest that traumas spe-
cific to women increase their self-protectiveness. Worldwide, one
in three women suffers domestic or sexual violence; 20% of girls
are sexually abused; and reproductive-related morbidity and mor-
tality are more frequent where women have fewer rights (WHO,
2014a). However, universally more men than women are exposed
to lethal threats (WHO, 2014a). If trauma alone were responsible
for greater self-protectiveness, then men should exhibit stronger
self-protective responses than women in some areas, such as in
response to violent social interactions or accidents which affect
men more (WHO, 2014a), but they do not (Ditlevsen & Elklit,
2012). Many of the sex differences we reviewed therefore are
not explicable by the trauma hypothesis.
Third, women’s greater self-protectiveness could result from
the high costs of pregnancy and lactation which could render
women less physically, socially, emotionally, and clinically func-
tional than men. This view is commonly held by medical and psy-
chological professionals who perceive “self-protective”reactions
as maladaptive or compensatory (Chesler, 1972; Cleghorn,
2021). If reproduction itself were the only critical factor however,
sex differences in self-protective reactions would be highest dur-
ing pregnancy and lactation, but this is not the case. Some sex dif-
ferences in self-protectiveness appear by infancy (e.g., immune
functioning, fear); others arise at puberty (e.g., smiling, sadness);
some are maximal throughout the reproductive years (e.g., neu-
roticism, migraine); and others increase with age (e.g., insomnia).
Fourth, worldwide men tend to hold higher status than
women, particularly in the public sphere (Fiske, Dupree,
Nicolas, & Swencionis, 2016; Rosaldo & Lamphere, 1974). This
difference almost certainly heightens females’self-protective reac-
tions compared to when females hold power such as within the
confines of families or in matrilineal societies (Smuts, 1992).
Status differences do not readily explain other socially self-
protective reactions, however, such as females’greater fearfulness
(Else-Quest et al., 2006) or more accurate emotional identification
(McClure, 2000) from infancy onwards.
In sum, the evolutionary explanation offered by SAT comple-
ments other accounts of women’s greater responses to threats by
integrating divergent domains. Further, it views females’strategies
as evolved adaptive functions, rather than being constrained fea-
tures that are sub-optimal compared to those of males. It also
helps resolve many apparent paradoxes in which women are
less likely than men to die from pathogens, injuries, social con-
flicts, and suicide, yet more likely to experience physical symp-
toms, pain, sleep disturbances, avoidance of social conflicts,
generalized worry, fear, disgust, and sadness, and make suicide
attempts. SAT posits that stronger self-protective reactions to
threat enhance survival, rendering females less vulnerable than
Figure 9. Sex differences in frequency of COVID-19 infections across varied demographic factors in England. © The Economist Group Limited, London (November
21, 2020).
20 Benenson et al.: Self-protection as an adaptive female strategy
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
males. Furthermore, SAT would predict that individuals who
assume primary responsibility for children’s well-being will
increase their self-protective reactions so as to enhance their
own survival.
7.4. Conclusion
Girls’and women’s heightened responsiveness to physical and
social threats, neuroticism, emotional reactions to threats, and
related clinical conditions are often pathologized, that is, attrib-
uted to hysteria, mental health disorders, or other abnormalities,
because men are the reference point (Chesler, 1972; Cleghorn,
2021). Our extension of Campbell’s SAT suggests, by contrast,
that females’“sensitivity”should be construed not as a con-
strained weakness or compromise enforced by reproductive biology
but as a strategic approach to counteracting threats. Male traits,
equivalently, that are often seen as the norm, are suboptimal for
enhancing survival, but serve to maximize men’sfitnessgiventhe
constraints that they confront (Seager, 2019). Thus, independent
consideration of each sex, along separate dimensions, is necessary
for understanding the ways in which each sex’s traits are optimized.
Had the evidence existed, we would have compared the reproduc-
tive success of females who varied in their degree of reactions to
threats, and not included males at all.
A richer understanding of the adaptive nature of female self-
protection ultimately will depend on discovering its underlying
mechanisms and how they may have co-evolved. Promising
mechanisms undergirding self-protectiveness include sex chro-
mosomes (Schurz et al., 2019), sex hormones (Klein &
Flanagan, 2016), centralized reactivity (Yunus, 2007), support of
attachment figures (Archer, 2008; Bowlby, 1980) and the larger
community (Smuts, 1992), and degree of responsibility for off-
spring survival (Allman et al., 1998).
In conclusion, in response to a wide diversity of threats,
human females exhibit greater self-protective responses than
males. This finding suggests an opportunity for researchers and
clinicians to better understand the adaptive nature of diverse
female traits, both in humans and other species.
Acknowledgements. The authors sincerely thank Dr. Barbara Finlay and
the six reviewers for their excellent recommendations which greatly improved
the manuscript.
Funding statement. This research received no specific grant from any fund-
ing agency, commercial or not-for-profit sectors.
Conflict of interest. None.
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Open Peer Commentary
Beyond individual sex differences:
“Staying alive theory”as an
adaptive complex
John Archer
School of Psychology and Computer Science, University of Central Lancashire,
Preston PR1 2HE, UK
jarcher@uclan.ac.uk
doi:10.1017/S0140525X22000577, e129
Abstract
Extended staying alive theory (SAT) raises the issue of the extent
to which its various attributes are linked or whether they provide
alternative means to the same adaptive ends. Theories such as
SAT that consider an array of sex differences may benefit from
the application of the multivariate Dstatistic, rather than using
aseriesofdvalues, as is common at present.
Most contemporary evolutionary explanations of sex differences
in aggression involve inter-male competition, a component of sex-
ual selection (Darwin, 1871/1901; Trivers, 1972). Campbell (1999)
departed from this by examining selection pressures on females,
proposing that sex differences in aggression and associated attri-
butes arose from selection pressures on females to facilitate stay-
ing alive, and consequently being more likely to rear their
offspring to maturity. The target article widened Campbell’s
“staying alive theory”(SAT) to include a range of self-protective
reactions to various kinds of threat. Extended SAT provides a
new way of considering attributes that are at present viewed indi-
vidually (often as pathologies), enabling them to be viewed as a
set of female adaptations.
The extended SAT raises the question of whether the specific
attributes covered, such as immune responses, pain thresholds,
emotions, and personality, form a coherent adaptive complex,
and if so whether they are linked to one another at an individual
level, so that someone with a strong immune response also shows
a low pain threshold and more sleep disturbances. Alternatively,
the various attributes covered by SAT may represent alternative
ways of achieving the adaptive end-result of facilitating female
longevity.
In psychology, discussions and syntheses of psychological sex
differences have typically focused on individual attributes rather
than coherent groups of attributes. This follows earlier syntheses
rooted in individual differences research (e.g., Garai & Scheinfeld,
1968; Maccoby & Jacklin, 1974), culminating in more recent times
with meta-analyses of specific attributes. These meta-analyses
were synthesized by Hyde (2005) and Zell, Krizan, and Teeter
(2015), both presenting sex differences as a list and calculating
the percentage that were of different magnitudes (large, medium,
small, or null). Conclusions were drawn on the basis of how many
of these attributes fell into the different categories. Links between
the individual attributes were not part of this approach, which is
essentially atheoretical.
In contrast, broad theoretical explanations, whether they be in
terms of social roles (e.g., Eagly, 1987; Wood & Eagly, 2012)or
evolutionarily based adaptive complexes, such as sexual selection
(Archer, 2019), or the extended SAT, raise the issue of how the
various attributes might be related to one another. The statistical
underpinning of sex differences viewed as sets of attributes, rather
than individual items, has only recently begun, following the work
of Del Giudice (2009). For example, from an evolutionary per-
spective, sex differences in aggression can be viewed as being
linked to other attributes that are the evolutionary consequence
of male competition, such as bodily strength (Sell, Eisner, &
Ribeaud, 2016; Sell et al., 2009). Likewise, the attributes consid-
ered in the revised SAT could be regarded as an adaptive complex
or as a series of alternative adaptations whose common function is
to minimize mortality in the sex that is the primary caretaker of
the offspring.
The meta-analyses and large-sample studies that form the
bases of existing syntheses of studies of sex differences are usually
concerned with specific attributes, such as aggression, or depres-
sion, and typically the summary statistic used is Cohen’sd, the
standardized difference between the mean values for males and
for females. This is appropriate for summaries where attributes
are viewed as independent items (e.g., Hyde, 2005; Zell et al.,
2015). However, where groups of coherent attributes are being
considered, it may be appropriate to consider such groupings
together and to apply the multivariate Dstatistic (Mahalanobis
distance), which represents the distance between the two sexes
in multivariate space. Despite some persuasive arguments that
this type of analysis is the appropriate way forward (e.g., Del
Giudice, 2009; Del Giudice, Booth, & Irwing, 2012; Eagly &
Revelle, in press), it has seldom been carried out in practice
(for exceptions, see Lippa [2001], for masculinity–femininity;
Conroy-Beam, Buss, Pham, & Shackelford [2015], for mate-
choice criteria).
Both the modified SAT theory, and my own evolutionarily
based review of sex differences (Archer, 2019), relied on the
more conservative approach of using dvales as summaries of
sex differences in individual attributes. This underestimates the
size of differences, so that when these are considered as groups
of attributes using the multivariate Mahalanobis D(Eagly &
26 Commentary/Benenson et al.: Self‐protection as an adaptive female strategy
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
Revelle, in press), much larger values are typically found than
when individual dvalues are averaged: One important caveat is
that larger Mahalanobis Dvalues are obtained where the individ-
ual attributes show lower intercorrelations. These observations
lead back to the empirical question of the extent to which individ-
ual attributes covered by SAT form a coherent grouping, or rep-
resent alternative responses that all have the consequence of
reducing mortality.
A final point is the extent to which the extended SAT com-
plements or replaces sexual selection as an evolutionary expla-
nation of human sex differences. In view of coherent sets of
male attributes (musculature, aggression, impulsiveness), it is
likely to be complementary, although this could be subject of
future study. To begin with, it would be a simple matter to
compare the scope of the present article to the attributes asso-
ciated with sexual selection in previous syntheses (e.g., Archer,
2019;Daly&Wilson,1988), and the extent to which these
two groupings were related or independent. The extended
SAT could also be applied to relevant within-sex variations:
We would predict that men showing greater degrees of
paternal care would score higher on attributes covered by the
modified SAT.
Financial support. This research received no specific grant from any fund-
ing agency, commercial, or not-for-profit sectors.
Conflict of interest. None.
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evidence of ecological adaptations in
human females
Toe Aung, Sojung Baek and David Puts
Department of Anthropology, The Pennsylvania State University, University
Park, PA 16802, USA
txa96@psu.edu
sjbaek1871@psu.edu
dap27@psu.edu
https://beel.la.psu.edu/
doi:10.1017/S0140525X22000541, e130
Abstract
Benenson et al. postulate that human females evolved unique
survival adaptations to facilitate maternal and grandmaternal
care. This hypothesis is consistent with the broader hypothesis
that female phenotypes are more ecologically optimal, but fur-
ther evidence is needed to make a compelling case that sex dif-
ferences in self-protection are not primarily the result of more
intense sexual selection on males.
Benenson, Webb, and Wrangham note that sexual selection
explains many traits of human males and suggest that “no unify-
ing theory explains traits expressed more in females.”They there-
fore propose a generalized version of Campbell’s“staying alive”
hypothesis: Human females evolved unique, self-protective sur-
vival adaptations driven by the importance of maternal and
grandmaternal care. Benenson et al. review evidence in support
of this hypothesis, including evidence that females live longer
and show less risk-taking behaviors, greater avoidance of interper-
sonal conflicts, lower pain thresholds, more effective immune
responses, and more frequent sleep disturbances.
We agree that theory and data suggest that human females
exhibit stronger self-protective reactions than males do, and that
these reactions were likely adaptive for ancestral females. These
ideas indeed help unify our understanding of some female adap-
tations –though not others, such as fat deposition on the breasts,
hips, and buttocks, which are putative sexually selected female
ornaments that may be costly to survival (Pawłowski &
Żelaźniewicz, 2021), and maternal investment through gestation
and lactation, which deplete energy reserves and decrease longev-
ity (Wood, 2017). Here, we make two additional points to
advance this discussion.
First, there is a more general theory that links a broader set of
human female traits: Females are the more “ecological sex”
(Gaulin & Sailer, 1985). While sexual selection favors traits that
aid in mating competition, ecological selection favors traits for
other functions, including survival, fecundity, and offspring sur-
vival. Gaulin and Sailer (1985) provided evidence that nutritional
factors influence the evolution of primate body size, but males
deviate further from the ecologically optimum size in species in
which they compete more intensely for mates. Gaulin and Sailer
(1985) note that the hypothesis that females tend to be more eco-
logically optimized “is a very general one. The idea that the pre-
cision of ecological adaptation will vary with both sex and
mating system suggests a functional perspective from which any
Commentary/Benenson et al.: Self‐protection as an adaptive female strategy 27
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
morphological, physiological, or behavioral pattern of sex differ-
ences might be studied”(p. 117). The hypothesis that females,
more than males, possess self-protective adaptations thus accords
well with the more general hypothesis that females are relatively
optimized under ecological selection compared to males in species
in which males experience stronger sexual selection.
Second, more evidence is needed to make a strong case that
specialized survival adaptations evolved in human females. Such
adaptations may instead have been selected in both sexes, with
a lower level of expression favored in males due to tradeoffs
with traits favored in mating competition, and many survival
adaptations are likely to be ancestral and not human specializa-
tions. Benenson et al. state that “it is not simply degree of mate
competition that produces sex differences in self-protectiveness,”
but the problem with inferring otherwise from the evidence
reviewed by Benenson et al. is that this evidence consists of
human sex differences in various traits, and sex differences can
result from adaptations in either sex. Without additional evi-
dence, a sex difference in the degree of mating competition
remains the more parsimonious explanation.
For example, Benenson et al. claim that greater female longev-
ity is an evolutionary response to women’s larger role in childcare,
but cross-species data are needed to pull apart contributions of
female parental investment from male sexual selection. In all
mammals, females engage in greater parental investment, but
males outlive females in approximately 40% of wild mammal
populations (Lemaître et al., 2020). Sex differences in longevity
appear to relate more consistently with the intensity of sexual
selection in males (Tidière et al., 2015), which may lead to male
phenotypes that are more susceptible to environmental threats
(Lemaître et al., 2020). Human sex differences in mortality due
to homicide, suicide, and accidents are also highest in young
adulthood when male mating competition is most vigorous
(Wilson & Daly, 1985).
Reduced female risk-taking and same-sex aggression are
shared with humans’close living relatives (Harrison, Noble, &
Jennions, 2021; Rohner, 1976), and sex differences in these traits
were likely present in the common ancestor of the great apes
because risk-taking and aggression increased male mating success
and the expense of survival (Archer, 2009; Carter & Kushnick,
2018; Flinn, Ponzi, & Muehlenbein, 2012; Kruger, Wang, &
Wilke, 2007; Luoto & Varella, 2021; Muñoz-Reyes et al., 2020;
Puts, Carrier, & Rogers, in press). Decreased responses to pain
and decreased pain sensitivity in males may also reflect an evolu-
tionary history of male–male mating competition (Archer, 2019;
Puts et al., in press; Vigil et al., 2013), and susceptibility to infec-
tious disease may be a costly side-effect of the development of sex-
ually selected male traits (Folstad & Karter, 1992; Moore &
Wilson, 2002).
Benenson et al. propose that sex differences in nighttime
awakenings and disturbances reflect heightened vigilance to
physical and social threats among women. However, mating
competition has also likely shaped patterns of sleep sacrifice
(Faria, Varela, & Gardner, 2019), and when sleep sacrifice is
used to protect the group against threats during nighttime, evo-
lutionary theoretical models predict that females should sleep
more, not less, than men (Faria et al., 2019). Some evidence indi-
cates that women sleep longer than men (Burgard & Ailshire,
2013) and have better sleep quality (Faria et al., 2019). In
BaYaka foragers (Kilius et al., 2021), males displayed a higher
variance in sleep patterns and spent more time socializing dur-
ing nighttime.
Relatively stronger ecological selection may indeed have
shaped specialized survival adaptations in human females
(Campbell, 2010; Stockley & Campbell, 2013), but further evi-
dence is needed to make a compelling case. Are these putative
survival adaptations more prevalent in primate species in which
females invest more in offspring, controlling for levels of male
mating competition? Are some unique to human females?
Many traits in human males, such as muscularity, low voice
pitch, and facial hair, emerge at puberty when male mating com-
petition intensifies (Aung & Puts, 2020; Puts, 2016). Do some
putative female survival adaptations emerge across pregnancy or
parturition, after female mating competition becomes less exigent
in relation to the importance of surviving to care for offspring?
We look forward to learning more.
Conflict of interest. None.
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Societies also prioritize
female survival
April Bleske-Rechekaand Robert O. Deanerb
a
Department of Psychology, University of Wisconsin-Eau Claire, Eau Claire, WI
54720, USA and
b
Department of Psychology, Grand Valley State University,
Allendale, MI 49401-9403, USA
bleskeal@uwec.edu
robert.deaner@gmail.com
https://bleske-rechek.com
http://faculty.gvsu.edu/deanerr
doi:10.1017/S0140525X22000528, e131
Abstract
We extend Benenson et al.’s hypothesis from the individual level
to the societal level. Because women have highly limited repro-
ductive rates, societies have generally prioritized female survival
and regarded males as expendable. We describe various lines of
evidence that are consistent with this hypothesis, and we offer
additional predictions about differential attitudes toward male
versus female endangerment.
In support of the general proposal that staying alive has histori-
cally been more important for females’reproductive success
than for males’(Campbell, 1999), Benenson et al. provide exten-
sive evidence that females respond to a variety of threats with
greater self-protectiveness than do males. We propose that the
logic of Benenson et al.’s analysis extends to the societal level.
In particular, because women, but not men, set the upper limit
on reproduction, societies have generally prioritized female sur-
vival and protection from harm.
We suggest that societies prioritize women because groups
with few men and many women produce more offspring, and
ultimately achieve greater success, than groups with few women
and many men (Baumeister, 2010; Felson, 2000). This idea is sup-
ported by historical and ethnographic data from both hunter
gatherers and large-scale societies (Glowacki, Wilson, &
Wrangham, 2020). A prioritization of female survival predicts
the existence of individual thought and behavioral patterns, as
well as group-wide norms, that promote the survival of women
over men. We note that the prioritization of female survival
does not imply a prioritization of female autonomy and sexual
choice.
Much evidence supports the hypothesis that societies prioritize
female survival. First, people’s self-reported attitudes reflect more
concern about preserving women’s survival than men’s. For
example, when asked who should be saved first on a sinking
ship, people are far more likely to say women than men
(FeldmanHall et al., 2016; see also Burnstein, Crandall, &
Kitayama, 1994). This attitude manifested on the sinking
Titanic, where men prioritized the survival of women and chil-
dren above their own, so much so that men traveling first class
were more likely to perish than were women traveling third
class (80% of men perished in all, compared to 25% of women;
Browne, 2007). This behavior has been observed on other sinking
ships, and the norm is indicated by written statutes and captains’
orders; in cases where men failed to prioritize women and chil-
dren, they were publicly shamed (Browne, 2007).
Warfare and military norms and attitudes prioritize female
survival. Worldwide, warfare has been pursued almost exclu-
sively by groups of men against other groups of men
(Chagnon, 1988;Keeley,1996). Historically, women have been
barred from military combat positions (in the United States,
women were banned from direct ground combat military posi-
tions until 2013), and in rare cases where industrialized states
have used women in combat, it has been done as a last resort
(Browne, 2007). The exclusion of women from combat reflects,
at least in part, concerns about their survival: Female combat
casualties cause greater societal despair than male casualties;
and male soldiers reported that if women were in their combat
units, they would feel more protective of them than of their
male comrades (Browne, 2007).
The workforce reveals trends consistent with a prioritization of
women’s survival. In the United States, men are massively over-
represented in the most dangerous jobs and they represent over
90% of occupational fatalities (Bureau of Labor Statistics, 2020,
2022). When emergencies pose grave risks to workers (e.g.,
Fukushima, Chernobyl), nearly all of the rescue workers are
men (ABC News, n.d.; Belyakov, Steinhäusler, & Trott, 2000).
Physically dangerous sports also do not generally include
women (Deaner & Smith, 2013). Although this may be due to
both informal social norms and sex differences in risk-taking, for-
mal policies exist: In both ice hockey and lacrosse, men but not
women are permitted to initiate physical contact against (i.e.,
check) their opponents.
Cognitive biases in perceptions of women are also consistent
with a prioritization of female survival. Males and females alike
are more likely to automatically categorize a “victim”as female
rather than male, to perceive the same offense as causing more
harm to females than to males, and to desire harsher punishment
to perpetrators who target female versus male victims (Reynolds
et al., 2020). Relatedly, people view an act of physical aggression
perpetrated against a woman as more serious than the same act
of aggression perpetrated against a man (Felson, 2000; Harris &
Knight-Bohnhoff, 1996), and offenders who commit violent
crimes against women receive longer sentences than do those
who commit crimes against men (Curry, Lee, & Rodriguez,
2004; Glaeser & Sacerdote, 2003).
Commentary/Benenson et al.: Self‐protection as an adaptive female strategy 29
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
The norm of (many) societies prioritizing the survival of
women could reflect cultural group selection (Richerson et al.,
2016; Turchin, Currie, Turner, & Gavrilets, 2013). However, it
could also reflect men protecting unrelated women and children
(“chivalry”) in order to signal their genetic quality, parenting abil-
ity, and general pro-sociality; this hypothesis is consistent with
data from nonhuman primates (van Schaik, Bshary, Wagner, &
Cunha, 2022).
One strength of the hypothesis that societies prioritize female
survival is that developmental mechanisms that operate at the
societal level may partly explain greater female self-protectiveness
at the individual level. For example, as summarized by Benenson
et al., girls and women generally experience greater fear than their
male counterparts; this difference likely has several causes, but
one may be societal messages that promote male, but not female,
bravery, pain tolerance, and risk taking, particularly if there is an
audience. These messages may be transmitted by family members,
other adults, and social narratives.
The hypothesis that women’s survival is prioritized generates
additional predictions about attitudes toward males and females,
including the following: (1) people should be more concerned
about women serving in direct combat positions than about
women serving in military command positions; (2) parents
should be less supportive of daughters’than sons’participation
in dangerous sports such as mixed martial arts and cliff-jumping;
(3) men and women should be less inclined to encourage females
than males to consider high-risk occupations, such as law enforce-
ment and truck driving; and (4) the degree to which people har-
bor negative feelings about female participation in direct ground
combat military roles and high-risk sports and occupations
should be mediated by their perceptions of how physically dan-
gerous those choices are as opposed to their perceptions of how
stereotypically male-oriented or unpopular those activities are.
Financial support. This research received no specific grant from any fund-
ing agency, commercial, or not-for-profit sectors.
Conflict of interest. None.
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Sex-dependent selection, ageing, and
implications for “staying alive”
Robert C. Brooksaand Khandis R. Blakeb
a
Evolution & Ecology Research Centre, School of Biological, Earth and
Environmental Sciences, The University of New South Wales, Sydney 2052, NSW,
Australia and
b
Melbourne School of Psychological Sciences, University of
Melbourne, Parkville 3010, VIC, Australia
rob.brooks@unsw.edu.au
khandis.blake@unimelb.edu.au
https://www.bees.unsw.edu.au/our-people/robert-brooks
https://findanexpert.unimelb.edu.au/profile/359342-khandis-blake
doi:10.1017/S0140525X2200053X, e132
Abstract
Incorporating theoretic insights from ageing biology could
advance the “staying alive”hypothesis. Higher male extrinsic
mortality can weaken selection against ageing-related diseases
and self-preservation, leading to high male intrinsic mortality.
This may incidentally result in female-biased longevity-promot-
ing traits, a possibility that will require rigorous testing in order
to disentangle from the adaptive self-preservation hypothesis
presented in the target article.
The authors, and the originator of the “staying alive”hypothesis
(Campbell, 1999), identify that sex differences in the timing of
male and female contributions to fitness can result in the
30 Commentary/Benenson et al.: Self‐protection as an adaptive female strategy
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
evolution of sex differences in survival and the mechanisms that
prolong life. The hypothesis seeks to explain women’s greater lon-
gevity as the result of female-specific longevity-promoting adapta-
tions. Those adaptations are thought to have evolved because,
relative to men, women have historically gained greater marginal
fitness from post-partum contributions to offspring and grand-
offspring fitness. This proposal complements the more commonly
articulated argument that stronger selection among men to suc-
ceed in pre-copulatory sexual competition leads them to take
more risks, be more violent, and thus die younger than women.
Our commentary points to some areas where “staying alive”
might be more thoroughly integrated with theory and empirical
research on ageing and life histories. Such integration would
allow both critical testing of “staying alive”and other human-
centric hypotheses and enrich the evolutionary study of sex-
dependent human ageing. Many of the background references
in the target article are from research on ageing, and many of
the traits discussed –including cancers, dementia, cardiovascular
diseases, autoimmune diseases, and age-dependent immune
responses –are related to ageing. Placing “staying alive”into
the theoretic context of ageing biology would constitute an
important next step for the hypothesis.
Ageing research has found value in distinguishing extrinsic
mortality due to age-independent hazards such as accidents and
general predation from intrinsic mortality due to age-dependent
decreases in performance (Kirkwood & Austad, 2000; Williams,
1957). While the distinction can often be artificial, it remains use-
ful in thinking about the evolution of mechanisms that slow or
prevent ageing, including immune and behavioural self-
protection. The fact that some extrinsic mortality is unavoidable
means that mechanisms of somatic repair are always going to
be under weaker selection in older cohorts than in younger ones.
This distinction is important because the reasons presented for
greater female lifespan in humans and in other animals are often
tied to greater extrinsic mortality in males. Higher predation due
to male ornamentation, accidents due to risk-taking, and male–
male aggression all have the potential to weaken the selection
against both diseases of ageing and self-preservation behaviours
in males relative to females (Austad & Bartke, 2016;
Bonduriansky, Maklakov, Zajitschek, & Brooks, 2008). High
male extrinsic mortality can thus lead on to higher intrinsic
mortality.
Observations across a variety of taxa suggest that such a pat-
tern may commonly pertain (see Bonduriansky et al., 2008 for a
review; Promislow & Harvey, 1990). In many taxa, males are
more likely than females to “live fast and die young”due to differ-
ences in the intensity of sexual competition (Promislow,
Montgomerie, & Martin, 1992). In humans, evidence suggests
that young men are particularly prone to discount the future
and risk their lives in the pursuit of status, wealth, and, ultimately,
matings (Wilson & Daly, 1985), and that women’s fitness is more
likely to benefit from long-term investment in children and
grandchildren (Hawkes, 2004).
Humans are, by any comparison, a long-lived species with
extended contributions from mothers, fathers, and alloparents
to offspring. Viewed in the context of other species, both
women and men have extraordinary self-preservation and anti-
ageing traits that drive very long mean and maximum lifespans.
Nonetheless, sex-differences in extrinsic mortality may be respon-
sible for sex-dependent patterns of intrinsic mortality, including
many of the traits reviewed in the target article. These traits
may be over-represented in women both because staying alive
enhances female fitness and because higher male extrinsic mortal-
ity has weakened selection in favour of these traits among men.
The claim that women’s fitness benefits more from self-
preservation than men’s fitness, while consistent with the major-
ity of evidence presented in the target article, is thus an empirical
claim that needs critical testing. Theoreticians and comparative
biologists have pointed out that in animal species in which
small numbers of males live long enough to grow large, develop
large weapons, or achieve high social rank, selection may promote
male lifespan and suppress male ageing more strongly than female
(Clinton & Le Boeuf, 1993; Graves, 2007). In humans, the impor-
tance of social status to men’s mating success may have a similar
effect, and has been suggested to be at least partly responsible for
the evolution of extended human lifespans (Tuljapurkar,
Puleston, & Gurven, 2007).
Further, although women’s life expectancy currently exceeds
men’s in most countries, that has not always been the case.
Throughout history, extraordinary numbers of women have
died in childbirth, and higher parities and costs of reproduction
are, in some places and at some times, associated with men living
longer than women (Bolund, Lummaa, Smith, Hanson, &
Maklakov, 2016; Maklakov, 2008).
Sex-differences in lifespan, age-dependent reproduction, and
thus selection are variegated, complex, and often environmentally
contingent. To add further complication, changes in the timing
of reproductive effort and in ageing-related traits can both pre-
cede and follow changes in survival (Austad & Bartke, 2016;
Bonduriansky et al., 2008). As a result, relationships between
selection on lifespan and the traits that result are often more com-
plex and confusing than the target article concedes. This is not a
criticism of a target article and the choices made under publishing
constraints, but rather a call for further theoretic development and
hypothesis testing.
In conclusion, the authors of the target article are to be
congratulated on assembling such a varied and thorough set of
published observations which, together, appear to weigh heavily
in favour of the “staying alive”hypothesis. Greater integration
with life history theories of ageing, and with the genomics of sex-
dependent variation in fitness traits (Bonduriansky et al., 2008),
together with a commitment to critically testing the adaptive intu-
ition behind the hypothesis will likely broaden its relevance and
spur a flurry of exciting research.
Financial support. The authors are supported by the Australian Research
Council, grants DP220101023 and DE210100800.
Conflict of interest. No conflicting interests declared.
References
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Staying alive includes adaptations
for catalyzing cooperation
Alessandra Cassara,b,c
a
University of San Francisco, San Francisco, CA 94117, USA;
b
Economic Science
Institute, Chapman University, Orange, CA 92866, USA and
c
Center for Effective
Global Action (CEGA), University of California at Berkeley, Berkeley, CA 94720, USA
acassar@usfca.edu
http://www.alessandracassar.net
doi:10.1017/S0140525X22000565, e133
Abstract
The target article interprets women’s lower competitiveness than
men’s as evidence of adaptation to help women avoid physical
conflicts and stay alive. This commentary advances the addi-
tional hypothesis that strategically suppressing competitiveness,
thus signaling egalitarian intentions, could be an adaptation to
catalyze cooperative behavior from males and females, turning
natural competitors (other women) into allies and men into sup-
portive partners.
Benenson, Webb, and Wrangham’s(2022) article interprets wom-
en’s lower competitiveness compared to men’s as evidence of an
adaptation that would permit females to avoid physical conflicts,
thereby helping them with staying alive (Campbell, 1999). Among
other strategies –such as smiling, politeness, and emotion identi-
fication –avoidance of confrontations is posited as having the
potential to reduce hostile interactions. Specifically, the argument
focuses on the results of competitiveness experiments in which
women are systematically determined less likely than men to
compete against others (Klege, Visser, Barron, & Clarke, 2021;
Niederle & Vesterlund, 2011; Sutter, Zoller, & Glatzle-Rutzler,
2019). It concludes that such behavior should reduce interper-
sonal conflicts and decrease social tensions. Recent economic evi-
dence suggests that we could take Benenson, Webb, and
Wrangham’s hypothesis one step further, and venture that
women not only avoid direct competition to reduce interpersonal
conflicts, but also to actively pursue strategies that increase the
opportunities to cooperate with others, both males (as mates or
potential romantic partners) and other females (as allomaternal
helpers). Such proactive prosocial strategy should be included as
another behavioral pillar of staying alive theory. Some evidence
in support of this hypothesis is as follows.
First, the competitiveness elicited by economics games is rem-
iniscent of labor markets, where confrontations rarely escalate to
the level of physical attacks. Individuals competing for CEO posi-
tions do not usually resort to eliminating contenders. Gaining
prestige, rather than physical violence, may be a more frequent
way to climb rank in the economic sphere (Cheng, Tracy,
Foulsham, Kingstone, & Henrich, 2013). This suggests an alterna-
tive hypothesis for why women shy away from competitive envi-
ronments: Such systematic preference could actually derive from
an evolved avoidance of situations with unequal distributions of
resources. Inasmuch as it produces non-egalitarian outcomes,
competitions may put further cooperation between winners and
losers at risk (Bartling, Fehr, Maréchal, & Schunk, 2009). Data
from a wide variety of experiments indicate that women are not
necessarily always more generous than men (Croson & Gneezy,
2009; Eckel & Grossman, 1998), but they do systematically prefer
equal distributions of resources and power more strongly than
men (Andreoni & Vesterlund, 2001; Dufwenberg & Muren,
2006; Fehr, Glätzle-Rützler, & Sutter, 2013; Selten & Ockenfels,
1998). Inequalities of resource, power, and status may erode coop-
eration based on reciprocity and mutual altruism, while egalitar-
ianism could be a critical factor for the evolution of strong
reciprocity and cooperation (Andreoni, Harbaugh, &
Vesterlund, 2003; Boehm, 1999; Bowles, 2006; Dawes, Fowler,
Johnson, McElreath, & Smirnov, 2007; Fehr, Fischbacher, &
Gächter, 2002; Hooper, Kaplan, & Jaeggi, 2021). Cooperation
based on reciprocity may have been especially relevant for
women who, for large part of human history, had to leave their
family, reside with their husbands’kin, and rely on non-kin and
strangers for help (Kaplan, Hill, Lancaster, & Hurtado, 2000;
Seielstad, Minch, & Cavalli-Sforza, 1998). So, rather than compet-
itiveness per se, women may be particularly susceptible to non-
egalitarian distributions of resources. If egalitarianism is a catalyst
for sustained cooperation, as both theory and experimental evi-
dence suggest, and cooperation based on reciprocity is more
attuned to women than to men, women may actively try to pro-
tect its potential by avoiding environments that create inequalities.
Second, the lower female competitiveness reported in eco-
nomic experiments is mainly observed when women compete
against men or in mixed groups (e.g., Geraldes, 2020).
Importantly, recent research shows emerging evidence of the
costs borne by women who compete and succeed in the economic
and political arenas, penalties felt both on the household front
and with same-sex individuals. Women who obtain high status
in society by reaching high-executive and political positions
appear not to gain commensurate advantages in attracting higher
quality men (Fisher, 2013; Fisman, Iyengar, Kamenica, &
Simonson, 2006), are more likely to get divorced than men
(Folke & Rickne, 2016), are subject to adverse reactions from
their partners, and report lower marital satisfaction (Bertrand,
Kamenica, & Pan, 2015). Furthermore, for women, having more
status, power and resources may alienate the support from other
women (Benenson, 2013; Benenson & Markovitz, 2014). Yet, the
benefits to securing the continued support of resource-holding
mates and the assistance of other women are far-reaching for the
women’s own outcomes and their offspring’s(Geary,2000;Hrdy,
2009;Rucas,2017). Hence, strategically downplaying one’scompet-
itiveness may be a fundamental strategy –likely unconscious or the
32 Commentary/Benenson et al.: Self‐protection as an adaptive female strategy
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
result of self-deception (Von Hippel & Trivers, 2011)–for attract-
ing and maintaining mates, securing same-sex allies, and sustaining
their cooperation.
Third, lower female competitiveness is not a universal find (for
a review of this literature, see Cassar & Rigdon, 2021a). Even in
cultures and samples in which a competitiveness sex gap exists,
it responds to incentives and a change in the game rewards can
greatly reduce it. Namely, in a first series of experiments across
different cultures, substituting cash rewards with prizes that ben-
efit the children of the participants eliminates the difference in
competitiveness between mothers and fathers (Cassar, Wordofa,
& Zhang, 2016; Cassar & Zhang, 2021). In a second series of
experiments, adding a prosocial option (where the winners can
send some of their rewards to the losers) increases women’s com-
petitiveness to the men’s levels (Cassar & Rigdon, 2021a,2021b).
These findings suggest that it is not competitiveness per se that
women lack, but, rather, that women more than men are partic-
ularly interested and responsive to the social aspects of
competitions.
In conclusion, this body of evidence suggests that women may
strategically downplay their competitiveness not just to reduce
potentially dangerous interpersonal conflicts but, primarily, to
actively elicit cooperative behavior from both males and females.
In intra-sex competitions, by signaling egalitarian intentions,
women may turn natural competitors into supportive allies
based on reciprocity. In inter-sex competitions, the suppression
of competitiveness when facing a male (whose higher competi-
tiveness, on the contrary, may signal good male mate value)
would be an adaptation for catalyzing women–male cooperation
for “the formation of alliances to raise children.”Staying alive
requires the strategic reduction of competitiveness as an adapta-
tion for eliciting cooperation for the benefit of offspring.
Financial support. The research of mine discussed in this article received
funding from the National Science Foundation (SES#1919535) and the
University of San Francisco.
Conflict of interest. None.
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Toward a more domain-specific
conceptualization of female traits:
A commentary on Benenson et al.
(2022)
Courtney L. Crosby, Rebecka K. Hahnel-Peeters
and David M. Buss
Department of Psychology, The University of Texas at Austin, Austin, TX 78712, USA
clcrosby@utexas.edu,rhahnel@utexas.edu,dbuss@austin.utexas.edu
http://davidbuss.com
doi:10.1017/S0140525X22000450, e134
Commentary/Benenson et al.: Self‐protection as an adaptive female strategy 33
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
Abstract
Benenson et al. (2022) amass impressive evidence of robust sex
differences as support for expanding “staying alive”theory. We
argue for a broader and more domain-specific conceptualization
focusing on life history tradeoffs between survival and mating
success. Using three examples –women’s disgust, fear of rape,
and cultivation of bodyguards –we illustrate these tradeoffs
and suggest a broader theoretical framework.
Benenson, Webb, and Wrangham’s(2022) expansion of “staying
alive”theory (SAT; see Campbell, 1999) posits that females have
evolved an array of specific adaptations as defenses against sur-
vival threats that differ from those of men. They correctly, and
expertly, assemble an impressive suite of sex-differentiated phe-
nomena directly or plausibly linked to female survival. We suggest
that an adequate explanatory account must have life history trade-
offs between components tributary to reproductive success at its
core, which include both survival and mating success. We discuss
three examples of documented sex differences important for
women’s reproductive effort and survival: sexual disgust, fear of
rape, and the cultivation of social bodyguards.
Sexual disgust
Women experience robustly higher levels of sexual disgust than
men (Al-Shawaf, Lewis, & Buss, 2018; Crosby, Durkee, Meston,
& Buss, 2020; Tybur, Lieberman, & Griskevicius, 2009). The tar-
get article attributes women’s higher general disgust –which dif-
fers from more specific classes of disgust such as pathogen
disgust, sexual disgust, or moral disgust –to their greater need
to promote survival and avoid danger. One hypothesized function
of sexual disgust, however, is mate avoidance. Importantly, this
avoidance does not center around the avoidance of general danger
or threats. Rather, sexual disgust motivates the avoidance of
potentially harmful or sub-optimal mates (e.g., mates of lower
mate value or mates unlikely to invest in a woman and her chil-
dren), as well as mates who might be disease vectors (Crosby
et al., 2020; Tybur et al., 2009). Sexual disgust may, therefore, pro-
tect women against death by avoiding these specific categories of
mates. However, sexual disgust likely also protects women against
reproductive costs including the accumulation of sexually trans-
mitted infections or reputational damage, thus increasing her abil-
ity to secure high-quality mates in the future (e.g., Al-Shawaf
et al., 2018). Together, this suggests that women’s sexual disgust
adaptations are at least somewhat domain-specific and contribute
to components of both survival and mating success. It also high-
lights that a simultaneously broader and more domain-specific
conceptualization –beyond the more general formulation of
SAT –is needed for an adequate explanatory account of sex dif-
ferences in disgust.
Fear of rape
Women face dramatically higher risks of sexual coercion and its
accompanying hazards to survival and reproduction than men.
Sexual conflict theory predicts that sex-specific adaptive problems
create sex-specific selection pressures producing co-evolved
defenses (Buss, 2017; Parker, 2009). Women’s fear of rape is
one hypothesized defense against sexual coercion costs.
Women’s fear of rape protects against hazards associated with
sexual exploitation including the circumvention of mate choice
and physical damage incurred during rape (reproductive and sur-
vival costs, respectively; Perilloux, Duntley, and Buss, 2012).
Women’s fear of rape tracks the age at which victimization is
most likely. For example, women between the ages of 19 and 35
express more rape fear than older women (Warr, 1985).
Conversely, older women are more fearful of being mugged
than being raped (Buss, 2021). Formidability mediates women’s
fear of rape such that women who perceive they could successfully
escape an attack display less rape fear (Gordon & Riger, 1989;
Pryor & Hughes, 2013).
While women’s rape fear was not discussed in the target arti-
cle, the authors reviewed several findings on women’s greater lev-
els of fear responding to social threats compared to men –a
domain-general conceptualization. The specificity of findings of
women’s greater rape fear, such as predictable age gradients and
female formidability findings, suggest that explanatory frame-
works for women’s fear require (1) their contribution to both sur-
vival and mating components of reproductive success, and (2) a
more domain-specific conceptualization of fear beyond that
offered by SAT.
Cultivation of social bodyguards
As a final example, consider the findings that women prioritize
the cultivation of bodyguards in mate and friend selection.
Women, more than men, prefer social alliances who are physically
formidable (Meskelyte & Lyons, 2022; Snyder et al., 2011)–asex
difference not mentioned in the target article. Bodyguards, we
suggest, have been and continue to be critical for women’s sur-
vival and mating success. They offer unique functions including
deterring physical and sexual assaults and reducing damage fol-
lowing assaults. These protections buffer against the survival
and reproductive costs of sexual coercion (Buss, 2021)–again
suggesting that explanatory accounts should consider the specific
ways in which women’s adaptations contribute to the multiple
components of fitness, and tradeoffs therein, beyond the domain-
general invocation of survival.
Conclusion
The target article describes an impressive array of documented sex
differences in physiological, psychological, and emotional
responses that are plausibly tributary to survival over human evo-
lutionary history. We applaud the authors for expanding SAT to
explain the evolution of these sex differences. We suggest that
many important adaptive problems recurrently faced by women
over evolutionary history contain fitness consequences for both
survival success and mating success, and tradeoffs therein, and
thus argue for a broader and more domain-specific conceptualiza-
tion of these adaptations.
Financial support. No funding was received for this commentary.
Conflict of interest. We have no conflicts of interest to disclose.
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Women take risks to help others to
stay alive
Alice H. Eagly
Department of Psychology, Northwestern University, Evanston, IL 60208, USA
eagly@northwestern.edu
https://psychology.northwestern.edu/people/faculty/emeritus/profiles/alice-
eagly.html
doi:10.1017/S0140525X22000437, e135
Abstract
Evidence that women voluntarily expose themselves to some
threats more than men do challenges the generalizability of
the claim that women exceed men in self-protective responses.
Examples include women’s higher rates of living organ donation
and rescuing Jews during the holocaust. In general, women’s
efforts to keep other people alive can take precedence over
their efforts to protect themselves.
The principle that women, more than men, engage in self-
protective reactions to threats is impressively documented by
Benenson, Webb, and Wrangham, but their analysis is incom-
plete. They fail to acknowledge that women, sometimes more
than men, put themselves in danger to preserve the lives of others
or reduce their suffering. To contribute to a more complete
account of the psychology of gender, I note and analyze some
examples of women endangering themselves to protect others
from suffering or death.
The first example derives from the excellent records for living
organ donation, which consists primarily of kidney donation
(Prasad, 2018; U.S. Organ Procurement and Transplantation
Network, 2021). Medical considerations favor greater male
donation, given men’s higher rate of end-stage renal disease
(Hsu, Iribarren, McCulloch, Darbinian, & Go, 2009) combined
with the greater transplant success when donor and recipient
sex are the same (e.g., Mudalige, Brown, & Marks, 2022).
Nevertheless, since U.S. record keeping began in 1988, living kid-
ney donations have been more common among women than men
(60%), as are living donations of all organs (61%). This disparity
has gradually increased in the United States, with 2020 data show-
ing 65% women among living donors for kidneys and for organ
donations overall. In addition, Kurnikowski et al. (2021) reported
a 16-nation average of 55% female donors with considerable var-
iation across these nations.
Donating an organ while alive presents nontrivial risks to
donors. Even though death or major postoperative problems
are rare (Choi et al., 2021), less serious complications, such as
gastrointestinal discomfort, bleeding, respiratory difficulties,
and surgical or anesthesia-related injuries are more common
(e.g., 17% of donors in a U.S. study; Lentine, Lam, & Segev,
2019). Concerning long-term outcomes, living kidney donation
is associated with glomerular hyperfiltration, predisposing
donors for the development of chronic kidney disease, resulting
in greater risk for end-stage renal disease (O’Keeffe et al., 2018).
Specific to women, kidney donation is also associated with
increased risk of preeclampsia, gestational hypertension, and
preterm birth (Bellos & Pergialiotis, 2022). Finally, economic
consequences can include lost wages, child care expenses, and
out-of-pocket medical costs (Fu, Sekercioglu, Hishida, &
Coyte, 2021). In summary, living organ donation can threatens
donors’health and well-being beyond the immediate stresses
of surgery.
Women placing themselves in danger to help others is also evi-
dent in the rescue of Jews in the occupied countries of Europe
during World War II, actions often punishable by death or confi-
nement in concentration camps (Becker & Eagly, 2004). The res-
cued Jews were often coworkers or friends of the rescuers, but
some were strangers (e.g., Gilbert, 2003; Oliner & Oliner, 1988).
Some rescuers gave short-term help, but many formed long-term
relationships by hiding Jews within their own dwellings.
Records of such rescues exist in the Yad Vashem archive of
data on non-Jews who rescued Jews. Becker and Eagly’s(2004)
analysis of these records suggested that women and men partici-
pated approximately equally overall. However, after excluding
married couples from the rescuer samples because the relative
responsibility of husbands and wives is unknown, significantly
more women than men served as holocaust rescuers in the
three occupied nations with the largest number of rescuers:
Poland, the Netherlands, and France.
Volunteer activities typically attract more women than men and
can present threats to volunteers, although these are rarely life-
threatening. Notably, women are the majority of volunteers both
in the United States (Turner, Klein, & Sorrentino, 2020)andworld-
wide (United Nations, 2018). The U.S. Peace Corps provides one
example: Women constitute 65% of its volunteers (Peace Corps,
2021). This service is associated with health risks such as malaria
and exposure to violence, which can include physical and sexual
assault (Peace Corps, 2022). Infectious gastroenteritis was the
most common illness among volunteers, followed by respiratory
and pulmonary conditions, and behavioral health problems such
as stress and anxiety (Peace Corps, 2018). Such humanitarian volun-
teering, which is disproportionately undertaken by women, thus can
present threats to health and wellbeing (see also Dahlgren, DeRoo,
Avril, Bise, & Loutan, 2009).
Commentary/Benenson et al.: Self‐protection as an adaptive female strategy 35
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
In summary, women are more likely than men to take risks in
some settings in which their voluntary actions put them in some
danger but directly benefit one or more other persons.
Nevertheless, men are far more likely than women to risk their
lives in extremely dangerous acts of rescue that are widely recog-
nized as heroic (e.g., rescues in fires and serious accidents; Becker
& Eagly, 2004). Causes may include not only men’s greater phys-
ical prowess, but also their lower fearfulness in dangerous real-
world settings and their greater tendency toward risky impulsivity
(see review by Archer, 2019). Such actions can bring public recog-
nition and even major accolades such as the Carnegie Medal for
Heroism or the Canadian Medal of Bravery, which are received
mainly by men (Eagly, 2009).
Other causes of sex/gender disparities in prosocial actions may
reflect the greater tendency of women than men to exhibit empa-
thy (see review by Archer, 2019), given that holocaust rescuing
and humanitarian aid generally involve serving people who differ
from oneself in characteristics such as religion and nationality.
Such service may reflect universalistic themes of shared humanity
that are common in religious and ethical systems (Post, 2002). If
so, women’s greater participation would be consistent with their
greater religiosity (Beit-Hallahmi, 2003) and commitment to uni-
versalistic values (Schwartz & Rubel, 2005). Exploration of such
influences and their possible links to evolutionary processes will
contribute to understanding how women and men balance pro-
tecting themselves and taking risks that benefit others.
These demonstrated sex/gender differences in the types of risks
undertaken disproportionately by women or men call for theories
that encompass both nature and nurture. Accounting for sex and
gender effects that vary across situations, cultures, and historical
time benefits from regarding female and male behavior as regu-
lated by nurture (e.g., gender roles and social expectations) and
nature (hormonal and other biological processes) (Eagly &
Wood, 2012,2013). Such an integrative perspective could shed
light on the question of why sex/gender differences in putting
oneself in danger versus avoiding danger depend on the setting
and the purpose of risky actions as well as well as the cultural con-
text including its gender norms (Eagly, 2009).
Financial support. This research received no specific grant from any fund-
ing agency, commercial, or not-for-profit sectors.
Conflict of interest. None.
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An expanded “staying alive”theory
(SAT) underplays complexity in
Homo sapiens
Agustín Fuentes
Department of Anthropology, Princeton University, Princeton, NJ 08540, USA
afuentes2@princeton.edu
https://anthropology.princeton.edu/people/faculty/agustin-fuentes
doi:10.1017/S0140525X22000449, e136
Abstract
The target article takes myriad human female patterns and
aligns them as a unit emerging from an expanded version of
“staying alive”theory (SAT). Females and males do differ, how-
ever, to treat the complexity of human response to threats as an
36 Commentary/Benenson et al.: Self‐protection as an adaptive female strategy
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
explicit, evolved sexually dimorphic package is not reflective of
current knowledge regarding health, sex/gender, and behavior
in Homo sapiens.
Campbell’s“staying alive”theory (SAT) argues human females
produce stronger self-protective reactions to aggressive threats
because self-protection has higher fitness value for females. The
SAT’s core assumption is that female and male humans are
under such distinct evolutionary pressures that selection struc-
tures females’bodies and minds producing “unique”adaptations
relative to males. The target article takes myriad patterns (behav-
ioral, physiological, social, cultural) in human females and aligns
them as a unit emerging from an expanded version of the SAT.
Human females and males do respond in overlapping but differ-
ent distributions to threats, pathogens, and related health chal-
lenges, but why this is the case is extremely complex and
influenced by multiple and diverse social, historical, biological,
and contextual variables.
There are patterned differences between males and females in
many species. For example, most mammalian females live longer
than males and there are a number of processes that affect female
longevity including sex chromosome heterogamy/homogamy and
telomere length (Xirocostas, Everingham, & Moles, 2020) and
diversity and complexity in female life histories and behavior
(e.g., Cooke, 2022; Morbeck, Galloway, & Zihlman, 1996).
However, this article seeks not to complexify understandings of
human behavioral variation, but to simplify them. And therein
lies my first critique. Benenson et al.’s core assertion, and the
assumptions of the SAT, rest heavily on the classic arguments
by Bateman, Trivers, Hamilton, and others, about the relative
costs of reproduction and their effects on parental investment
and life histories. While these assumptions about evolutionary
“costs”of being female and male remain common in biology text-
books, there are serious challenges to their precision and univer-
sality. Bateman’s thesis, and work, is flawed and the realities of
measuring and assessing relative costs of investment in reproduc-
tion and the implications/consequences for male and female
behavior are complex (Drea, 2005; Gowaty, Kim, & Anderson,
2012; Tang-Martinez & Ryder, 2005). This complexity of patterns
is especially true for humans (Borgerhoff-Mulder, 2004) given our
complex neurobiologies (Eliot, Ahmed, Khan, & Patel, 2021), and
distinctive sex/gender (Hyde, Bigler, Joel, Tate, & van Anders,
2018), life history (Sear, 2020), and morphological (Dunsworth,
2020) processes. Specifically, parental investment in humans is
more complex than the authors of this article acknowledge, and
the potential evolutionary implication of this reality is not taken
into account in their assessments. While noting complexity in
human reproductive processes the authors’still frame their
argument around assumptions of costs/benefits arising from a
nuclear family/two-adult-plus-offspring core reproductive unit,
which is not the basal form of residence, social organization, or
childcare in humans (Gettler, 2016; Rosenberg, 2021; Sear,
2021). They do acknowledge “grandmothering”and “cooperative
care,”but emphasize that females do most childcare in contempo-
rary societies, and leave it at that. However, these assessments
(from the HRAF and contemporary forager/horticulturalist
groups) might not reflect the range and structures of human evo-
lutionary, and contemporary, processes related to reproduction
and energetic investments and their integration into the broader
range of human social behavior (Borgerhoff-Mulder & Rauch,
2009; Fuentes, 2016; Fuentes & Wiessner, 2016; Spikins, 2015).
There are other, equally valid, modes of explanation for human
social organization and behavioral processes not solely grounded
in assumptions of radically different evolutionary trajectories for
females and males. The bottom line is that given current under-
standings of human evolution, physiology, and behavior one
should question, and unpack, the basal framework of the SAT
more extensively before building an entire thesis on it.
My secondary critique involves the evidence offered in sup-
port of the authors’argument. For example, the causes of mor-
tality in Figure 2 are all prevalent with substantive impact
primarily in the recent evolutionary moment (post-last demo-
graphic transition and post-industrial revolution). The WHO
data suggest that on average females die later or less from cer-
tain diseases, but to understand morbidity and mortality of can-
cers or cardiovascular disease (CVD) or hepatitis A solely, or
even primarily, as the outcome of evolved differences between
male and female biology is to elide decades of research and
scholarship on the myriad interconnecting social, economic,
historical, and biological processes at play (Krieger, 2020).
Similarly, coronavirus disease-2019 (COVID-19) is a particu-
larly bad example as social structures and inequities are central
in structuring outcomes of morbidity/mortality in pandemics/
syndemics (Gravlee, 2020). Patterns of race, sex/gender, geogra-
phy, region, and so on mortality from COVID are not the best
locale to investigate female/male biological differences.
Obviously, biological factors related to reproduction can be
involved, but their relative contributions to the patterns and
processes of the outcomes in the face of the societal/structural
determinants of health are often relatively small, and often non-
linear. I do not have the space to engage the psychological and
social behavior differences the authors review (e.g., smiling,
politeness, sadness, anger, avoidance of confrontation, etc.).
But, to see these as direct outcomes, and measures, of selection
for behavioral differences in females and males due to differen-
tial patterns of reproductive investment is to ignore vast
amounts of social scientific and ethnographic data/analyses on
why/how humans smile, get mad, avoid specific kinds of social
contexts, and so on. Of course, evolutionary histories affect
these behaviors, but it stretches credulity to assume gender/
sex differences in these behaviors are best represented as specific
outcomes of targeted selection.
The authors are not ignorant of these critiques. In sections
7.2 and 7.3 they acknowledge complexity and state “we cannot
specify which characteristics of sex/gender relate to self-
protection.”But if this is the case, isn’tthatallthemorereason
to avoid simple and strictly targeted selection models such as the
SAT? It is likely that many of the processes highlighted, includ-
ing aspects of SAT, are at play in contemporary humans. But to
compartmentalize them as a unit and focus on only one selec-
tion model, as if its explanatory power is more meaningful, is
to oversimplify and misrepresent the dynamics of the human
processes being explored. In sum, to treat the complexity of
human response to threats as an explicit, sexually dimorphic
package being driven by a relatively simple selection hypothesis,
the SAT, is not reflective of the immense body of knowledge
regarding health, sex/gender, reproduction, and behavior in
Homo sapiens.
Financial support. This research received no specific grant from any
funding agency, commercial, or not-for-profit sectors.
Conflict of interest. None.
Commentary/Benenson et al.: Self‐protection as an adaptive female strategy 37
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
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Staying alive enhances both
women’s and men’s fitness
Renée V. Hagen, Delaney A. Knorr, Sally Li,
Ashley Mensing and Brooke A. Scelza
Department of Anthropology, University of California, Los Angeles, Los Angeles,
CA 90095, USA
reneehagen@ucla.edu;d.knorr@ucla.edu;sallyli@g.ucla.edu;anm2186@g.ucla.
edu;bscelza@anthro.ucla.edu
doi:10.1017/S0140525X22000553, e137
Abstract
We argue that Benenson et al. need to consider not only sex dif-
ferences in the effects of care on offspring survival but also in
age-specific fertility when predicting how longevity affects fit-
ness. We review evidence that staying alive has important effects
on both women’s and men’s fitness, and encourage consider-
ation of alternative explanations for observed sex differences in
threat responses.
In their target article, Benenson, Webb, and Wrangham (2021)
expand upon Campbell’s(1999)“staying alive”hypothesis,
which reasons that because offspring survival is more tightly
linked to maternal than paternal care, women should place a
higher value on survival, and therefore exhibit stronger self-
protective responses to threat. Core to this argument is the idea
that, “survival is more fitness enhancing for females than
males”(Benenson et al., 2021, p. 5). However, the original
Campbell hypothesis, and in turn Benenson et al.’s use of it
here, is not supported by our current understanding of human
life histories. We therefore argue that the staying alive hypothesis
is an insufficient explanation for their findings.
The staying alive hypothesis assumes that a reduction in life-
span is more damaging to women’s fitness than to men’s.
Importantly, this requires not only (1) a differential effect of
women’s and men’s mortality on the survival of existing offspring,
but also (2) that this difference is not outweighed by a sex differ-
ence in the effect of longer lifespan on having additional off-
spring. Only when both of these assumptions hold is it possible
that a gender-difference in the fitness value of longevity could
drive differences between women and men in survival-promoting
behaviors. Campbell’s hypothesis focuses exclusively on the first
assumption, ignoring the second. Here we use demographic
data to examine the effects of survival on both the well-being of
existing offspring and the prospects for future offspring.
First, we agree with Benenson et al. (2021) that mothers’care is
more strongly correlated with offspring survival than is fathers’.
Cross-culturally, maternal death has a much stronger negative
effect on child survival than paternal death (Hill & Hurtado,
2009; Sear & Mace, 2008). The involvement of fathers in their
children’s upbringing varies across populations and paternal
care can more easily be replaced by the care of another alloparent,
such as a grandparent or other kin, than maternal care (Boyette,
Lew-Levy, Sarma, Valchy, & Gettler, 2019; Meehan, Helfrecht, &
Quinlan, 2014; Sear & Mace, 2008). Combined with the uncer-
tainty men have of their genetic relatedness to alleged offspring,
which can be a disincentive for investment, it follows that wom-
en’s survival has greater effects on offspring well-being than
men’s, especially for young children. However, this fact alone is
not enough to conclude that women’s fitness is more strongly
dependent on their survival than men’s. For this, we need to
assess the second assumption by considering sex differences in
fertility across the life course.
In most human populations, men’s fertility peaks later and
declines more slowly with age than women’s. Demographic data
collected by Blurton Jones (2016) and further analyzed by
Muller et al. (2020) indicate that among Hadza hunter–gatherers
in Tanzania, men’s age-specific fertility (ASF) is highest at 33,
compared to 26 for women. Women’s reproductive careers start
early but halt with the onset of menopause around age 50,
while men’s begin later but are characterized by an extended fer-
tile period lasting into their seventies (Muller et al., 2020).
Demographic samples across a variety of subsistence modes
show the same pattern, with men’s ASF peaking later and declin-
ing more slowly than women’s (Marlowe, 2000; Nisén,
Martikainen, Silventoinen, & Myrskylä, 2014; Tuljapurkar,
38 Commentary/Benenson et al.: Self‐protection as an adaptive female strategy
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
Puleston, & Gurven, 2007). This amounts to a substantial effect of
later-life fertility on men’s fitness. Furthermore, Tuljapurkar et al.
(2007) show that these differences in men’s and women’s fertility
curves impact senescence. Their model shows the human aging
pattern reflects selection for survival for as long as men reproduce.
These differences in ASF curves reflect a variety of cultural and
demographic processes: Men tend to be older than women at
marriage, men are more likely to remarry than women, and in
some societies polygyny allows older men to monopolize
women of reproductive age. Furthermore, the same processes of
sexual selection that Benenson et al. (2021) emphasize, where
male competition for resources drives mating access, can lead to
these age differences. It takes time to accrue wealth and status,
shifting mens’reproductive careers later and enhancing prospects
for later-life fertility when men are often in the best position to
compete.
These data show that survival has different but important con-
sequences for men’s reproductive success. The potential for older-
age fertility strongly increases the value of staying alive for men.
How this weighs against women’s payoffs for continued reproduc-
tion and childcare is an empirical question that cannot be
answered easily with the currently available data. However, we
posit that while for women longevity is critical for helping existing
offspring to survive, for men staying alive longer can have impor-
tant effects on the total number of offspring they father. Both fac-
tors need to be considered when determining whether survival is
more fitness-enhancing for one sex than the other.
We encourage serious consideration of the alternative explana-
tions offered by Benenson et al. (2021) when aiming to under-
stand the drivers of the observed sex differences in
self-protective behavior, including women’s increased vulnerabil-
ity to physical threats due to their smaller body size and lower sta-
tus. Additional factors that we expect to play a role are cultural
notions of masculinity and femininity that may shape how
women and men respond to threatening situations as well as
how they self-report behavioral and emotional responses to
threats.
Financial support. The authors received no external funding specific to this
research.
Conflict of interest. All authors declare that they have no conflicts of
interest.
References
Benenson, J. F., Webb, C. E., & Wrangham, R. W. (2021). Self-protection as an adaptive
female strategy. Behavioral and Brain Sciences, Accepted manuscript, 1–86. https://doi.
org/10.1017/S0140525X21002417
Blurton Jones, N. G. (2016). Demography and evolutionary ecology Hadza hunter gather-
ers. University of California, Los Angeles.
Boyette, A. H., Lew-Levy, S., Sarma, M. S., Valchy, M., & Gettler, L. T. (2019).
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Republic of the Congo. American Journal of Human Biology,32(4), e23342. https://
doi.org/10.1002/ajhb.23342
Campbell, A. (1999). Staying alive: Evolution, culture, and women’s intrasexual aggres-
sion. The Behavioral and Brain Sciences,22(2), 203–214.
Hill, K., & Hurtado, A. M. (2009). Cooperative breeding in South American
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Feldblum, J. T., …Pusey, A. E. (2020). Sexual dimorphism in chimpanzee (Pan
troglodytes schweinfurthii) and human age-specific fertility. Journal of Human
Evolution,144, 102795. https://doi.org/10.1016/j.jhevol.2020.102795
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10.1371/journal.pone.0000785
Somatic maintenance/reproduction
tradeoffs and human evolution
Kristen Hawkes
Department of Anthropology, University of Utah, Salt Lake City, UT 84112, USA
hawkes@anthro.utah.edu
doi:10.1017/S0140525X22000474, e138
Abstract
The authors propose that many morbidities higher in women
than men are adaptations protecting survival, selected because
survival has been especially crucial to mothers’reproductive suc-
cess. Following their lead, I pursue variation in tradeoffs between
reproduction and survival recognized by Darwin that were likely
central to the evolution of many traits that distinguish us from
our great ape cousins.
Benenson, Webb, and Wrangham’s (BWW) extension of
Campbell’s(1999) staying alive theory (SAT) is a welcome elabo-
ration of likely sex differences in fitness-related tradeoffs. Both the
Origin (1859) and Descent (1871) show Darwin’s own recognition
of variation in tradeoffs that account for astonishing diversity in
the living world. He lacked tools to understand how inheritance
works but still saw enormous phenotypic consequences of sexual
reproduction’s“one mother, one father for each offspring”foun-
dation. That foundation is now usually called the Fisher condi-
tion, as Fisher (1930) combined Mendelian inheritance with
natural selection to show that each sex contributes half the ances-
try of future generations. Although it is fertile females –not males
–limiting the number of babies, offspring sex ratios are usually
near even because two haploid gametes, ovum and sperm, form
each diploid zygote. If males are rare, the average reproductive
success of rare males is higher than the female average. Then
mothers tending to produce more males average more grandchil-
dren, erasing the male rarity.
The Fisher condition also explains why sex ratios in the fertile
ages determine which strategies dominate mating competition.
Campbell (1999) countered textbook claims that with typical
sex roles males compete while females care: males are ardent,
females coy. She cited Hrdy (1979,1981,1986), Smuts (1987,
1995), and Wrangham (1980) for evidence of libidinous and com-
petitive female primates, with different resources limiting fitness
for each sex: food and safety for females, paternities for males.
Those differences contributed to Campbell’s SAT and BWW’s
extension here.
Commentary/Benenson et al.: Self‐protection as an adaptive female strategy 39
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
Variations in tradeoffs between reproduction and survival were
taken up by Williams’(1957) field-defining paper that explained
why natural selection results in differing rates of aging across the
living world. Williams (1966) later modeled costs to survival
imposed by current reproduction showing selection favors a “nor-
mal reaction”adjusted to the actor’s age and sex by fitness gains
expected from additional allocation to current reproduction or to
survival instead. Williams called the likely fitness value of the lat-
ter residual reproductive value (more on reproductive value in
Hawkes, 2020a).
These tradeoffs are important for all sexual reproducers but
their distinctive importance in human evolution is the topic
here. Darwin saw phenotypic evidence of our phylogenetic close-
ness to great apes, now confirmed by genetics placing us all in the
same hominid family. In all living hominids female fertility usu-
ally ends before age 50 –but great ape females age faster than
women and usually die while still cycling. Humans differ in our
postmenopausal longevity, later maturity, yet faster rate of baby
production. A grandmother hypothesis to explain those distinc-
tive traits uses ethnographic observations of grandmothers’forag-
ing subsidies (Blurton Jones, 2016; Hawkes, O’Connell, & Blurton
Jones, 1997,2018) and theory developed to explain the broad var-
iation in female mammal life histories (Charnov, 1991,1993;
Hawkes, O’Connell, Blurton Jones, Alvarez, & Charnov, 1998;
O’Connell, Hawkes, & Blurton Jones, 1999). In two-sex agent-
based models of that hypothesis, grandmothers’subsidies propel
the evolution of a great ape-like life history to a human-like one
(Kim, Coxworth, & Hawkes, 2012,2014,2019). Increased longev-
ity also shifts the sex ratio in the fertile ages from the female-bias
typical of mammals to the male-bias in humans as proportions of
both post-fertile women and older still-fertile men expand
(Coxworth, Kim, McQueen, & Hawkes, 2015). When mating
sex ratios are female-biased, males pursuing multiple mates gain
more paternities; with the bias reversed, claiming and guarding
a mate against other males wins more paternities (Loo, Chan,
Hawkes, & Kim, 2017a; Loo, Hawkes, & Kim, 2017b; Loo,
Weight, Hawkes, & Kim, 2020; Loo, Rose, Hawkes, & Kim,
2021; Rose, Hawkes, & Kim, 2019; Schacht & Bell, 2016).
All of this follows ancestral grandmothers’subsidies adjusting
the fitness maximizing tradeoffs between somatic maintenance
and current reproduction. More somatic allocation results in
more grandmothering subsidies, shortening birth intervals.
Ancestral mothers’bearing next babies sooner poses survival chal-
lenges for their previous infants recognized by Hrdy (2009; see also
Hawkes, 2014). She saw the precocious social responsiveness that
makes human babies so engaging as an adaptive consequence of
those challenges. Added to the maturity delaying effects of lower
adult mortality, slower neural maturation expands final brain size
and also proportion neocortex across the mammals (Finlay &
Darlington, 1995; Workman, Charvet, Clancy, Darlington, &
Finlay, 2013). The combination of earlier weaning with slower neu-
ral maturation would have wired distinctive priorities for shared
understanding in ancestral infancy (Finlay, 2019; Finlay &
Uchiyama, 2017;Hawkes,2020b; Hawkes & Finlay, 2018).
BWW suggest their SAT’s relevance to the male–female
health-survival paradox: Where data are available, women’s lon-
gevity is almost always greater than men’s even though morbidi-
ties are higher in women than men (Alberts et al., 2014). If the
morbidities BWW explore are actually protective that could
resolve the paradox. If increased longevity was favored in our lin-
eage as ancestral grandmothering displaced the independent
mothering of other great apes, our postmenopausal life stage
also had consequences for sexual selection (O’Connell, Hawkes,
Lupo, & Blurton Jones, 2002). More fertile old men competed
for paternities (Coxworth et al., 2015) with preferences for mating
younger females that distinguish men from chimpanzees (Muller,
Emery Thompson, & Wrangham, 2006,2020). Ethnography
shows older men usually hold substantial advantages over youn-
ger ones (Collier & Rosaldo, 1981; Hawkes, 2000; Marlowe &
Berbesque, 2012; Rodseth, 2013). That alters males’fitness trade-
offs between current reproduction and somatic maintenance.
Formal two-sex models of the grandmother hypothesis expose
sexual conflict over longevity (Chan, Hawkes, & Kim, 2016,
2017; Kim et al., 2012,2014) with male advantages for greater
longevity pushing the compromise longevity higher than an equi-
librium without males (Hawkes, 2020a).
If BWW’s expansion of SAT brings more attention to the evo-
lution of human postmenopausal longevity, more attention to con-
sequences for paternity competition might follow. Yet the topic of
sexual selection in human evolution can seem unwelcome where
broader gender identities are now celebrated. Expanded apprecia-
tion of sexual fluidity can make Darwin’s recognition of “competi-
tion among the males for possession of the females”seem to glorify
toxic masculinity and obscure gender diversity. Yet Darwin’stheory
of natural selection including sexual selection is central to under-
standing human evolution. It helps explain pervasive conflicts of
interest –and our distinct appetite for shared understanding, an
appetite that inflates antagonisms –but can also defuse them.
Acknowledgments. I’m grateful to Megan Mullineaux and Jim O’Connell
for insights and editorial advice.
Financial support. No special funding supported preparation of this
comment.
Conflict of interest. I have no conflict of interest.
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“Staying alive”in the context of
intimate partner abuse
Courtney Humeny
Institute of Cognitive Science, Carleton University, Ottawa, Ontario K1S 5B6,
Canada
Courtney_humeny@carleton.ca
doi:10.1017/S0140525X22000504, e139
Abstract
Females are disproportionately affected by intimate partner
abuse that can result in severe physical and mental harm.
Benenson et al. provide little exploration of how female-evolved
traits enhance females’survival in abusive relationships.
Discussion centres on “why”females do not “just leave”an abu-
sive relationship and the effectiveness of female-evolved traits in
navigating intimate partner abuse over time.
Benenson et al. provide a compelling case that corroborates
Campbell’s“staying alive”theory. Substantial evidence was over-
viewed to support Benenson et al.’s claim that females invest more
resources in reducing social conflict and protecting social bonds
through various strategies (e.g., politeness, emotion identification)
that enhance their survival. While I generally agree with Benenson
et al.’s conclusions, I would like to extend them to the context of inti-
mate partner abuse.
Benenson et al. acknowledge that females are disproportion-
ately affected by gendered violence, particularly intimate partner
abuse (Conroy, 2021). Yet it is unclear how female-evolved traits
enhance their survival in abusive intimate relationships and if this
is associated with “why”females do not “just leave”a relationship
once it becomes abusive. Evidence suggests that the risk for vio-
lence is heightened when females leave or attempt to leave an abu-
sive intimate relationship, with more than half of femicide being
committed by a current or former intimate partner (Conroy,
2021; Petrosky et al., 2017). Femicide is found to be the leading
cause of death of females in the pregnancy and post-partum
period in the United States (Wallace, Gillispie-Bell, Cruz, Davis,
& Vilda, 2021). Further, Johnson, Eriksson, Mazerolle, and
Wortley (2019) found, in a sample of males incarcerated for femi-
cide, that 50% did not perpetrate physical abuse in the year lead-
ing up to the femicide but exhibited coercively controlling
Commentary/Benenson et al.: Self‐protection as an adaptive female strategy 41
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
behaviours (e.g., jealousy, stalking). Thus, severe violence and
even femicide can occur even when escalating injuries from phys-
ical assaults are absent.
It could be argued that females do not immediately leave an
abusive relationship as it could be safer to stay and wait for a
less dangerous time for separation (e.g., once they have developed
good coping skills, secured transportation/shelter/finances;
Walker, 2009). During this time, they may use female-evolved
traits to adapt to their environment. These include their enhanced
sensitivity and reactivity for threat-related cues (e.g., abuser’s
expressions of anger) and proficiency for emotion identification
that may aid them in learning their abuser’s triggers to navigate
the cycle of abuse and mitigate confrontation. While these strate-
gies could diminish the severity of abuse episodes, they may not
be self-protective over the long term. Particularly because females
can be in an abusive relationship for extended periods (with stud-
ies reporting relationships lasting over 20 years; Eckstein, 2011;
Humeny, Forth, & Logan, 2021), which heightens the risk for
severe forms of abuse and detrimental consequences for females’
mental and physical health (Mechanic, Weaver, & Resick, 2008).
This includes acute and chronic pain from injuries (e.g., traumatic
brain injury, maxillofacial injuries; de Macedo Bernardino et al.,
2018; Smirl et al., 2019).
Even if abusers do not perpetuate physical abuse, chronic
stress from the cycle of abuse and abusers’coercively controlling
behaviours increase females’isolation (Walker, 2009) and sus-
ceptibility for mental health disorders, including post-traumatic
stress disorder and depression (Karakurt, Patel, Whiting, &
Koyutürk, 2017). Substantial evidence suggests post-traumatic
stress disorder and depression impedes facial affect recognition
(Cotter et al., 2018; Moser et al., 2015) and emotion regulation
(Plana, Lavoie, Battaglia, & Achim, 2014; Vanderlind, Millgram,
Baskin-Sommers, Clark, & Joormann, 2020), contributes to cog-
nitive impairments (e.g., attention, working memory) and social
withdrawal (Cotter et al., 2018; DePierro, D’andrea, & Pole,
2013; Schweizer & Dalgleish, 2011), and impairs the processing
of “safe environments”(i.e., hinders processing of socially affirm-
ing information, reduces approach behaviours; Nawijn et al.,
2015). Karakurt et al. (2017) found intimate partner abuse
survivors demonstrated elevated rates of gynaecological and
pregnancy-related problems, including injuries from sexual
assault, sexually transmitted diseases, low birth rates, and late
entry and/or inconsistent pre-natal care. Intimate partner abuse
also contributes to reduced immune system functioning
(Karakurt et al., 2017), decreased sleep quality (Lalley-
Chareczko et al., 2017), and enhanced risk of cardiovascular dis-
ease and all-cause mortality (Chandan et al., 2020).
Since intimate partner abuse is associated with a heightened risk
of all-cause mortality, staying in an abusive intimate relationship
impedes survival and reproductive success. This is further evident
via the effects of chronic stress and injury on mental and physical
health, which appear to hinder the effectiveness of female-evolved
traits (e.g., emotion identification proficiency) that may aid in nav-
igating the cycle of abuse. Given the prevalence of intimate partner
abuse and the effects it has on females’survival and reproductive
success, Benenson et al.’s argument would benefit from including
a discussion of how Campbell’s“staying alive”theory applies to
intimate partner abuse. One avenue would be to explore the asso-
ciation between female-evolved traits and their social networks that
were established prior to the abusive relationship.
Benenson et al.’s findings parallel research that shows females
have more intimate and reciprocal interpersonal relationships
(Pearce, Machin, & Dunbar, 2021) and rely on a wider array of
family and friends for mutual support than males (Conrad &
White, 2010; Einolf, 2011). Females are also found to have
more positive help-seeking attitudes than males (Mackenzie,
Gekoski, & Knox, 2006). Males’adherence to traditionally mascu-
line norms (e.g., risk taking, self-reliance, dominance) is associ-
ated with less help-seeking behaviours and declines in mental
health (Wong, Ho, Wang, & Miller, 2017). Sylaska and Edwards
(2014) found females had a higher rate of disclosing intimate
partner abuse than males and tended to disclose to friends and
female family members. Disclosure, coupled with the reception
of social support (e.g., emotional or tangible forms, such as shel-
ter, childcare, and/or financial resources), was predictive of
improved mental health (Sylaska & Edwards, 2014). It has also
been found to mitigate the isolation caused by intimate partner
abuse and serve as a protective mechanism against continued
abuse (Bybee & Sullivan, 2005). While females may have a wide
social network and a willingness to disclose and seek help it is
important that their support network is equipped with the appro-
priate resources to assist them in safely navigating and/or exiting
an abusive relationship. Thus, continued education and commu-
nity outreach, complete with community and institutional
resources (e.g., risk assessments, reducing stigmatization, ensuring
housing and employment stability), is necessary. These factors
could provide survivors a safe environment for disclosure and
help-seeking that may aid in mitigating the severe negative out-
comes that can result from intimate partner abuse.
Financial support. This research received no specific grant from any fund-
ing agency, commercial, or not-for-profit sectors
Conflict of interest. None.
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Only as a last resort: Sociocultural
differences between women and
men explain women’s heightened
reaction to threat, not
evolutionary principles
Jeffrey R. Huntsinger and Akila Raoul
Department of Psychology, Loyola University Chicago, Chicago, IL 60660, USA
jhuntsinger@luc.edu
araoul@luc.edu
http://jeffreyhuntsinger.weebly.com/index.html
doi:10.1017/S0140525X22000516, e140
Abstract
The target article proposed that women display greater self-pro-
tectiveness than men to major physical and social threats
because such self-protective responses have higher fitness value
for women than men. Rather than having evolutionary roots,
we suggest the various physiological, behavioral, and emotional
responses to social and physical threats exhibited more by
women than men are instead rooted in sociocultural forces.
“This biological principle [adaptation] should be used only as a last resort.
It should not be used when less onerous principles …are sufficient for a
complete explanation”(p. 11; George Williams, 1966,Adaptation and
Natural Selection)
In their target article, Benenson, Webb, and Wrangham introduce
an impressively broad model that emphasizes the evolutionary
origins of gender differences in self-protective responses to major
physical and social threats. Here we offer another way of under-
standing such differences. We propose the various physiological,
behavioral, and emotional responses to social and physical threats
exhibited more by women than men are instead rooted in status
and power differences as well as gender stereotypes, roles, and
norms.
Social role theory provides the theoretical scaffolding for our
argument and suggests that gender differences arise through gen-
der socialization and the placement of men and women in differ-
ent roles in society (Wood & Eagly, 2002). According to the
theory, basic biological differences between women and men,
including differences in childbearing, physical strength, and size,
led to a historical and contemporary division of labor (i.e., differ-
ent social roles) in society. Social structural features, particularly
power and status differences associated with the different social
roles women and men occupy, are the primary cause of observed
differences between the sexes. This division of labor accounts for
why women are more communal and men are more agentic.
Women are primarily responsible for domestic labor and child-
care, even when employed, leading them to be more communal.
Men are primarily responsible for work, leading them to be
more agentic. This division of labor leads to different beliefs
about women and men (e.g., stereotypes) and how they should
behave (e.g., gender roles and norms). From this view, women’s
self-protective responses to social and physical threat result
from sociocultural forces, including women’s lower status and
power in society, gender stereotypes, and gender roles and rules.
In what follows we briefly review evidence consistent with this
view. Before continuing, however, it is important to point out
what we are not saying. We are not disputing that the human
brain is a product of evolution. That is trivially true. Social role
theory is a “biosocial constructionist theory”that proposes that
cultural processes interact with evolutionary forces (Eagly &
Wood, 2013; Wood & Eagly, 2002). The question is how and in
what ways evolutionary forces shaped women and men, not
about whether such forces had an influence.
The authors of the target article cite research showing that
women report greater pain, both when experimentally induced
in the laboratory and clinically. The authors suggest that this is
an evolved self-protective response to physical threat on the
part of women, however, research demonstrates such differences
are mediated, in part, by gender roles (Sanford, Kersh, Thorn,
Rich, & Ward, 2002). In this case, gender differences in femininity
predicted pain tolerance and perception. A similar role for gender
Commentary/Benenson et al.: Self‐protection as an adaptive female strategy 43
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
roles in pain can be found across many studies (Fillingim, King,
Ribeiro-Dasilva, Rahim-Williams, & Riley, 2009). Further, both
women and men have the stereotype that women are more sensi-
tive to pain and more willing to report pain. Such stereotypes pre-
dict sex differences in pain tolerance and perception (Fillingim
et al., 2009).
The authors cite research showing that women tend to smile
more, they are more polite, and they are better able to identify oth-
er’s emotions during social interaction than men. The authors sug-
gest these differences are an evolved self-protective response to
social threats on the part of women. However, research shows
that such differences are shaped by sociocultural forces. There are
strong sex-based norms for smiling, with smiling being more
acceptable for women because women are supposed to be commu-
nal and expressive (LaFrance, Hecht, & Paluck, 2003). Women also
smile more than men due to their social roles within society. Sex dif-
ferences in smiling are reduced when men and women occupy the
same social role (LaFrance et al., 2003). Research demonstrates that
gender roles and rules can explain women’s greater ability to decode
the emotional expressions of others (Brody & Hall, 2008), and their
greater use of tentative speech (Kalbfleisch & Herold, 2006).
The authors argue that greater self-reports of negative emotion
by women reflect a greater reaction to threat, however great cau-
tion should be taken when interpreting sex differences in self-
reported emotion. Many studies show that on retrospective self-
reports women report greater general emotionality as well as
experiencing specific emotions with greater frequency. These dif-
ferences disappear when emotional experiences are measured in
the moment (i.e., online emotion reports; Robinson & Clore,
2002). Daily diary studies that capture emotion dynamics in
real time, for example, find no differences in the emotional lives
of women and men (Barrett, Robin, Pietromonaco, & Eyssell,
1998). In other research, women and men in the laboratory played
a word game competition where some participants were asked
their emotional reactions immediately after the game, and others
reported them a week later. Results showed no gender differences
in immediate online emotional reports, but a stereotypic pattern
of emotional report was evident at 2 weeks (Robinson, Johnson,
& Shields, 1998). These and other studies suggest that the emo-
tional lives of women and men are nearly identical.
Many of the various other self-protective reactions mentioned
in the target article have also been explained via mechanisms
other than evolutionary ones. Women’s lack of social power and
gender roles makes them more vulnerable to depression
(Nolen-Hoeksema, 2001). Due to their lower status and gender
roles, they face more chronic strains and stressors in their lives
than men, making them more likely to develop depression since
the experience of stressful life events strongly contributes to
depression. Gender roles and rules also play a role in gender dif-
ferences in anxiety disorders (McLean & Anderson, 2009).
Increased stress can also have detrimental impacts on immunity,
contributing to differences between women’s and men’s stress
responses (Verma, Balhara, & Gupta, 2011).
We conclude by suggesting the authors may have prematurely
jumped to evolutionary conclusions when other sufficiently com-
plete explanations, in this case gender differences in status and
power, gender roles and rules, are readily available.
Financial support. This research received no specific grant from any fund-
ing agency, commercial, or not-for-profit sectors.
Conflict of interest. None.
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699–727.
Harm or protection? Two-sided
consequences of females’
susceptible responses to
multiple threats
Jingyuan Lina,b,c , Pim Cuijpersc, Hong Lia, b
and Yi Leib,d
a
Centre for Studies of Psychological Applications; Guangdong Key Laboratory of
Mental Health and Cognitive Science; Key Laboratory of Brain Cognition and
Educational Science, Ministry of Education; School of Psychology, South China
Normal University, Guangzhou Guangdong, China;
b
Institute for Brain and
Psychological Sciences, Sichuan Normal University, Chengdu, Sichuan, China;
c
Department of Clinical, Neuro and Developmental Psychology, Amsterdam
Public Health Research Institute, Vrije Universiteit Amsterdam, The Netherlands
and
d
Center for Language and Brain, Shenzhen Institute of Neuroscience,
Shenzhen, China
linjingyuan921@126.com
p.cuijpers@vu.nl
lihong_psych@m.scnu.edu.cn (Hong Li, corresponding author)
leiyi821@vip.sina.com (Yi Lei, corresponding author)
https://scholar.google.com/citations?user=ImW-nwoAAAAJ
https://www.pimcuijpers.com/blog/
https://www.researchgate.net/profile/Hong-Li-67
https://www.researchgate.net/profile/Yi-Lei-7
doi:10.1017/S0140525X22000607, e141
44 Commentary/Benenson et al.: Self‐protection as an adaptive female strategy
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
Abstract
The target article presented a plausible argument that females’
susceptibility to threats might be self-protection for staying
alive, but some evidence requires scrutiny. We need to consider
(1) the biases of narrative reviews, (2) subjective life quality, and
(3) the shadow side of extreme reactions to threats before con-
cluding that females’threat-based response is a self-protection
mechanism that promotes survival.
We want to congratulate Benenson, Webb, and Wrangham (2021)
with their important Campbell’s(1999)“staying alive”theory and
why this may explain the gender/sex gap in psychopathology.
However, we also have some concerns about this approach.
Although the narrative approach these authors used is often used to
summarize a research field, the criteria for selection of studies to
include are not explicit (Cuijpers, 2016). More detailed criteria for
which studies were included and which not would be a helpful addi-
tion for readers to get an overall impression of this research field.
It is well-known that the sex/gender binary has been exten-
sively questioned and studied (Morgenroth & Ryan, 2021) by neu-
roscientists, psychologists, and researchers in behavior and
neuroendocrinology (Li, Yuan, & Lin, 2008; Yuan, Luo, Yan,
Meng, Yu, 2009; Hyde, Bigler, Joel, Tate, & van Anders, 2019;
Lin et al., 2021). Hence, to minimize bias from the sex/gender
binary, it is also important to consider multiple genders’
responses to threats and their associations with life-related prop-
erties instead of focusing on sex/gender comparisons between
females versus males only. Moreover, we propose reconsidering
the structure of “staying alive”beyond survival or life expectancy
to get a more comprehensive relevant premise and evidence base
of a field for further research. Some relevant evidence on these
issues exists that we briefly review below.
As the target article reviewed, accumulated evidence has shown
that women live longer than men as measured by life expectancy,
but they were more likely to experience negative emotions and ill-
ness. For life expectancy, it is predicted that the female advantage
will shrink by 2030 in at least 30 countries (Kontis et al., 2017).
Furthermore, there is another authoritative health index, the
so-called “healthy life expectancy”(Salomon, Mathers, Murray,
& Ferguson, 2001), focusing on the quality of life spent in a
healthy state (Robine, Michel, & Branch, 1992). This index indi-
cates a gender gap at just a 0.9-year difference in favor of
women, which is considerably smaller in terms of healthy life
years than overall life expectancy (OECD, 2013). Therefore, one
reservation is that longer life expectancy is a quantified form of,
but may not be synonymous with, staying alive. It is also essential
to consider the associations of qualitative facets of staying alive
(e.g., life satisfaction, quality of life, subjective well-being, etc.)
with susceptible responses to threats.
The target article also reviewed convincing evidence on female
protective responses (e.g., smiling, politeness, identification of
others’emotions) to social threats, contributing to psychological
well-being and quality of life. Smiling, politeness, and compassion
are indeed positive signs of prosocial intentions and increase
socially perceived attractiveness (Gangestad & Scheyd, 2005),
which helps gain more social support in most aspects of life
(Becker & Srinivasan, 2014; DeYoung, Quilty, & Peterson,
2007). Support from friends has been found to be positively
linked with maternal life satisfaction (Luthar & Ciciolla, 2015).
Perceived social support benefits single mothers’well-being, and
is linked with positive development outcomes in the child
(Taylor & Conger, 2017). In contrast, lower maternal life satisfac-
tion leads to a high risk of child behavior problems in the future
(Totsika et al., 2013). These pieces of evidence also support female
responses to threats as a self-protective consequence for them-
selves and their children.
However, the evidence does not comprehensively support the
protective role of female reactions to some socioeconomic threats.
For example, in the medical workplace, burnout affects nearly half
of US physicians and disproportionately affects women who
report lower satisfaction with the pressure of work–life integration
than men (Cunningham, 2008). Women are more likely to expe-
rience unemployment than men, inhibiting subjective well-being
and leading to physical and mental diseases (Iacovides, Avidon,
Bentley, & Baker, 2014).
Several clinical conditions (e.g., depression and anxiety) occur
more frequently in women than men. How does the staying alive
theory explain the reproductive significance of mood and anxiety
disorders caused by extreme responses to threats? Perinatal depres-
sion, a depressive episode during pregnancy and after the birth of a
child is a good example (Drury, Scaramella, & Zeanah, 2016). It is
estimated that around one in seven women in high-income coun-
tries and one in 10 women in low-income countries are affected
by perinatal depression (Woody, Ferrari, Siskind, Whiteford, &
Harris, 2017). Perinatal depression has clear negative effects on
the infant and child development in cognitive, emotional, behavio-
ral, and physical outcomes and leads to a considerable reduction in
maternal quality of life (Cuijpers et al., 2021). Complications of
untreated perinatal depression include maternal suicide (Slomian,
Honvo, Emonts, Reginster, & Bruyère, 2019). Therefore, it appears
to threaten instead of protecting new female parents and their off-
spring’s survival and fitness.
In summary, it is easy to find counterexamples to dispute the
viewpoint that females’reactions to threats are adaptive self-
protection. Meanwhile, the limitations of the staying alive theory
for interpreting the clinical consequences of extreme reactions to
threats should be identified with caution. It seems that susceptible
responses to threats have both protective and harmful impacts on
female life expectancy and life quality. We would like to acknowl-
edge the authors have outlined the abundant essential evidence
that serves important roles for future studies to explore, identify,
and manipulate the potential moderators for promoting self-
protective aspects and reducing negative impacts.
Financial support. The commentary is supported by the following: Ministry
of Education Key Projects of Philosophy and Social Sciences Research [grant
number 21JZD063]; Guangdong Key Project in “Development of new tools
for diagnosis and treatment of Autism”[2018B030335001]; National Natural
Science Foundation of China [NSFC31871130]; the National Science and
Technology Innovation 2030 –Major program of “Brain Science and Brain-
Like Research”[2021ZD0200520 and 2021ZD0200531]; Shenzhen Science
and Technology Research Funding Program [JCYJ20200109144801736].
Conflict of interest. None.
References
Becker, D. V., & Srinivasan, N. (2014). The vividness of the happy face. Current
Directions in Psychological Science,23(3), 189–194. doi: 10.1177/0963721414533702
Benenson, J. F., Webb, C. E., & Wrangham, R. W. (2021). Self-protection as an adaptive
female strategy. Behavioral and Brain Sciences,1–86. doi: 10.1017/S0140525X21002417
Campbell, A. (1999). Staying alive: Evolution, culture, and women’s intrasexual aggres-
sion. Behavioral and Brain Sciences,22(2), 203–214. doi: 10.1017/S0140525X99001818
Cuijpers, P. (2016). Meta-analyses in mental health research: A practical guide.
Commentary/Benenson et al.: Self‐protection as an adaptive female strategy 45
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
Cuijpers, P., Franco, P., Ciharova, M., Miguel, C., Segre, L., Quero, S., & Karyotaki, E.
(2021). Psychological treatment of perinatal depression: A meta-analysis.
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Female advantage in threat
avoidance manifests in threat
reaction but not threat detection
David S. Marchaand Lowell Gaertnerb
a
Department of Psychology, Florida State University, Tallahassee, FL 32306-
4301, USA and
b
Department of Psychology, University of Tennessee, Knoxville,
TN 37996-0900, USA
march@psy.fsu.edu,gaertner@utk.edu
https://psy.fsu.edu/faculty/marchd/march.dp.php
https://psychology.utk.edu/faculty/gaertner.php
doi:10.1017/S0140525X22000462, e142
Abstract
Threat avoidance involves both detection of a threatening stim-
ulus and reaction to it. We demonstrate with empirically vali-
dated stimuli (that are threatening, nonthreatening-negative,
neutral, or positive) that threat detection is more pronounced
among males, whereas threat reactivity is more pronounced
among females. Why women are less efficient detectors of threat
challenges Benenson et al.’s conceptual analysis.
Benenson et al. suggest that females have a stronger self-protective
capacity to avoid survival threats than do males. A more general
threat-superiority literature suggests that humans inherited a neu-
ral architecture that preferentially processes and responds to
immediate survival threats (of phylogenetic or ontogenetic origin;
Blanchette, 2006; March, Gaertner, & Olson, 2018a,2018b;
LeDoux, 2012; Öhman & Mineka, 2001). Such threat-superiority
manifests as earlier detection and stronger responses to threaten-
ing than non-threatening stimuli. For example, March, Gaertner,
and Olson (2017) empirically validated four categories of stimulus
images –threatening (e.g., snarling predators, gunmen),
nonthreatening-negative (herein “negative,”e.g., bugs, wounded
animals), positive (e.g., puppies, babies), and neutral (e.g., door-
knobs, mugs) –and found that the threatening stimuli were iden-
tified faster, more frequent targets of initial eye-gaze, and elicited
stronger startle-eyeblinks. Conceptually similar patterns occur
when threat superiority is isolated from the opposing effect of
conscious attention by presenting stimuli outside conscious per-
ception (i.e., by using masked presentations at 14–21 ms;
March, Gaertner, & Olson, 2022). Not considered by the threat-
superiority literature, however, is the possibility of a sex difference
favoring females.
Benenson et al. focused primarily on reaction to, rather than the
detection of, threat. Accordingly, we reanalyzed data from four of
our studies: two that assessed stimulus detection and two that assessed
stimulus reaction. As a caveat, we powered our studies to test within-
subject effects of the stimuli not between-subject effects such as sex.
Moreover, sex imbalances among our college-student samples com-
promise inferential tests of sex differences. Consequently, we focus
on the effect size of the sex difference (Table 1).
The stimulus detection studies in the top half of Table 1 used
visual search and eye-tracking tasks. Each trial of visual-search
presented a 3 × 3 matrix containing a central “X”surrounded
by eight stimuli. On congruent trials, stimuli were all threatening,
all negative, all neutral, or all positive. On the critical incongruent
trials, either one threatening or negative stimulus was embedded
among seven positive or seven neutral stimuli. Participants
pressed one of two keys to indicate whether the stimuli were all
the same or not. Males were faster than females to detect the
incongruent threatening stimulus and the incongruent negative
stimulus. Each trial of the eye-tracking task presented a pair of
stimuli from different categories (e.g., threat and negative) and
assessed at which stimulus the participant first gazed. Males
were more likely than females to first gaze at a threatening than
negative or neutral stimulus, and to first gaze at a negative than
positive stimulus, with negligible differences on the remaining
46 Commentary/Benenson et al.: Self‐protection as an adaptive female strategy
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
pairings. These data suggest that males have an advantage over
females in the detection of threatening stimuli.
The stimulus reaction studies in the bottom half of Table 1
assessed startle eyeblink –a reflexive response measured by elec-
tromyography of the orbicularis oculi muscle (Blumenthal et al.,
2005). Each trial presented an image from one of the four stimu-
lus categories for 6,000 ms (in the first study) or 21 ms (in the sec-
ond). On critical trials, a 100 dB noise blast was presented via
headphones 2,000–4,000 ms after stimulus image onset to trigger
a startle-eyeblink. Females responded with a larger
startle-eyeblink than did males when the noise blast was paired
with threatening stimuli in the first and second studies and
with negative stimuli in the second study. Alternatively, males
responded with a larger startle-eyeblink than did females when
the noise blast was paired with neutral stimuli in the first and sec-
ond studies, with negative stimuli in the first study, and with pos-
itive stimuli in the second study. The only consistent pattern
across studies favoring females was in response to threat, which
supports Benenson et al.’s argument. That a consistently stronger
female response did not occur to other stimuli rules out the alter-
native of an invariantly stronger female response. The stronger
female response appears cued to immediate survival threats.
Our data support Benenson et al.’s argument in regard to reac-
tion to threat but not in regard to threat detection. The only
evidence Benenson et al. considered that could be construed as
threat detection was their section on pain tolerance. A sex differ-
ence in self-reported pain, however, could be compromised by
gender role expectations that differentially influence male versus
female reports (Robinson, Gagnon, Riley, & Price, 2003). Of
course, Benenson et al. did not buttress their argument solely
with self-report. Nonetheless, gender expectations could compro-
mise much of the self-report data they used (e.g., such as emo-
tions, sleep disruption, and picture aversion; Grossman &
Wood, 1993; Wong, Pituch, & Rochlen, 2006). Fortunately, the
threat detection and reaction tasks that we employed are not easily
compromised by gender role expectations. Reanalysis of our data
reveals a stronger female self-protective capacity to avoid survival
threats in regard to stimulus reaction but not stimulus detection.
Why males are more efficient than females at detecting immediate
survival threats requires further consideration by Benenson et al.
Financial support. This research received no specific grant from any fund-
ing agency, commercial, or not-for-profit sectors.
Conflict of interest. None.
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Women need to stay alive and
protect reproductive choice
Melissa M. McDonald and Rachel M. James
Department of Psychology, Oakland University, Rochester, MI 48309-4482, USA
mmmcdonald@oakland.edu
rmjames@oakland.edu
https://www.mcdonaldpeplab.com/
doi:10.1017/S0140525X22000486, e143
Table 1 (March and Gaertner). Sex differences in stimulus detection and
reaction
Source Task F
n
M
n
Stimulus d
Stimulus detection
Study 1
a
Visual
search
35 55 Thr −0.59
Neg −0.54
Study 2
a
Eye
tracking
29 34 Thr vs. Neg −0.18
Thr vs. Neu −0.16
Thr vs. Pos −0.03
Neg vs. Pos −0.15
Neg vs. Neu −0.09
Pos vs. Neu 0.08
Stimulus reaction
Study 3
a
Startle
eyeblink
94 28 Thr 0.35
Neg −0.20
Neu −0.18
Pos 0.08
Study 2
b
Startle
eyeblink
70 30 Thr 0.40
Neg 0.27
Neu −0.17
Pos −0.38
Note. F
n
= female sample size; M
n
= male sample size; Thr = threat; Neg = negative; Neu =
neutral; Pos = positive. Effect size dis scored so positive values reflect a stronger female
than male response and is the difference of the female mean minus the male mean divided
by their pooled standard deviation with the exception of the eye-tracking data for which we
converted the odds ratio of the sex difference in the tendency to first gaze at the stimulus
listed first vs. second to das ln(OR)/1.65 (Sánchez-Meca, Chacón-Moscoso, & Marín-Martínez,
2003). Sample size discrepancies from the source are because of currently excluding
participants who did not specify their sex and the reversed labeling of sex frequencies in
study 1 of March et al. (2017).
a
March et al. (2017).
b
March et al. (2022).
Commentary/Benenson et al.: Self‐protection as an adaptive female strategy 47
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
Abstract
Defense of reproductive choice is an important motivation in
women’s self-protection psychology for which the “staying
alive theory”cannot fully account. Evidence indicates that
some elements of women’s self-protection psychology function
to protect reproductive choice rather than survival, or may be
equally well explained by either motivation. Integrating perspec-
tives will result in greater explanatory breadth and precision in
theory testing.
Benenson et al. propose an extension of Campbell’s(1999) staying
alive theory (i.e., SAT), and marshal an impressive array of empir-
ical data to support their claims. We agree with the authors’the-
oretical premise, but suggest that in order to fully capture females’
self-protection psychology, the SAT must also address the impor-
tance of protecting reproductive choice. A key means by which
females increase reproductive fitness is through strong mate pref-
erences (Trivers, 1972). Yet, female choice is often thwarted by
males through sexual coercion and aggression (e.g., Brown,
1952; Chagnon, 1988; Minturn, Grosse, & Haider, 1969; Palmer,
1989; Rozée, 1993;Sanday,1981). Converging lines of evidence
suggest that this intersexual competition has generated selection
pressure for a psychological system in women designed to protect
reproductive choice (reviewed in McDonald, James, & Roberto,
2021). This is an important extension of the ideas proposed by
Benenson et al. for each of the reasons outlined below.
Not all self-protection functions to promote survival
Women express greater fear of personal crimes (e.g., murder,
assault, rape, burglary) than men (e.g., Ferraro, 1996; Franklin
& Franklin, 2009), despite the fact that women are victimized
less frequently for most such crimes, outside of rape (Craven,
1997; Rennison & Rand, 2003). Although these data align with
the SAT, women’s greater fear of personal crimes appears to be
driven more by the desire to protect reproductive choice than
to stay alive. Indeed, sex differences in fear of personal crimes
are eliminated or reversed when fear of rape is statistically con-
trolled, but not fear of murder (Ferraro, 1996; but see Lane &
Meeker, 2003). Described as the “shadow of sexual assault,”wom-
en’s greater fear of personal crimes is largely driven by a fear that
those crimes will co-occur with rape (Ferraro, 1995,1996; Fisher
& Sloan, 2003;May,2001; Warr, 1984,1985). Moreover, women’s
fear of rape often matches or exceeds their fear of murder
(Ferraro, 1995,1996; Warr, 1984). In short, the SAT is not suffi-
cient to fully explain the sex difference observed in fear of per-
sonal crimes.
Women’s fear of rape and their history of sexual assault are
also associated with self-protection behaviors aimed at reducing
the likelihood of becoming the victim of violent crime. For exam-
ple, women consume true crime media with greater frequency
than men, particularly when it has high information value for
self-protection (e.g., when it features female victims, describes
the perpetrator’s motives, and provides tips for escape; Vicary &
Fraley, 2010). This desire for self-protective information appears
to be rooted in women’s fear of rape. Indeed, women who express
a stronger fear of rape consume true crime media with greater fre-
quency, and do so with the explicit motivation to learn strategies
for defensive vigilance (McDonald et al., 2021). Although con-
sumption of true crime media may cause elevated rape fear, it is
plausible that the causal pathway is bidirectional. To that point,
women’s sexual assault history (unlikely to be the causal outcome
of true crime consumption) is positively associated with women’s
frequency of true crime media consumption and the motivation
to consume it for the purpose of defensive vigilance. In total,
there is good evidence to suggest that women who are particularly
fearful of rape engage in behaviors to protect their reproductive
choice.
A number of studies have also documented that women’s self-
protection behavior varies as a function of conception risk across
the menstrual cycle, a key factor that exacerbates the reproductive
cost of sexual assault. For example, studies have shown that
women at high risk of conception, relative to women at low
risk, are less likely to engage in sexually risky activities (Bröder
& Hohmann, 2003; Chavanne & Gallup, 1998), infer greater
threat from male strangers (Fessler, Holbrook, & Fleischman,
2014; Garver-Apgar, Gangestad, & Simpson, 2007), exert greater
handgrip strength in response to sexually threatening contexts
(Petralia & Gallup, 2002), and express greater bias against out-
group males (McDonald, Asher, Kerr, & Navarrete, 2011,2015;
Navarrete, Fessler, Fleischman, & Geyer, 2009). While a general
motivation for self-protection should be constant across the men-
strual cycle, the motivation to protect reproductive choice is most
pertinent on days when conception risk is elevated, indicating that
these findings are better explained by the motivation to protect
reproductive choice than the SAT.
The functions of self-protection behaviors may not be mutually
exclusive
Some of the data presented by Benenson et al. cannot be
easily explained by a motivation to protect reproductive choice
(e.g., women’s heightened immune response and lower pain thresh-
old), but others are somewhat ambiguous. For example, the higher
rate of nighttime awakenings among girls versus boys, and the
onset of this sex difference during puberty, suggests that such awak-
enings could also be explained by the protection of reproductive
choice. Given social and legal sanctions against rape, it is a behavior
often hidden at night (Waterhouse, Reynolds, & Egan, 2016).
Indeed, “nightcrawling”is a common form of rape in small-scale
societies in which men trespass into women’s homes to sexually
coerce, rape, and abduct women (Rozée, 1993;Sanday,1981).
Many of the findings highlighting women’s tendency to engage
in behaviors that reduce the risk of interpersonal conflict, such as
smiling, politeness, recognizing negative emotions, avoiding con-
frontation, and experiencing more threat-responsive negative
emotions, may also be seen as attempts to reduce the risk of sexual
aggression –particularly given the overlap in women’s fear of
crime and rape. Similarly, the tendency for women to score
more highly on measures of neuroticism may simultaneously
function to protect reproductive choice, given research showing
positive associations between neuroticism and women’s fear of
rape (McDonald, Coleman, & Brindley, 2019).
Conclusion
The expansion of the SAT is both a useful and powerful means of
explaining women’s self-protective psychology. However, a pure
emphasis on survival without the integration of the importance
of protecting reproductive choice, leaves some aspects of women’s
self-protection unexplained. Moreover, integrating reproductive
choice as an additional motivation for self-protection would
48 Commentary/Benenson et al.: Self‐protection as an adaptive female strategy
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
encourage research to engage in more precise theory testing to
determine whether the pattern of data is better aligned with gene-
ral self-protection motives or domain-specific self-protection
attuned to threats against reproductive choice.
Financial support. This research received no specific grant from any fund-
ing agency, commercial, or not-for-profit sectors.
Conflict of interest. None.
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Biological sex, by-products, and
other continuous variables
John G. Neuhoff
Department of Psychology, The College of Wooster, Wooster, OH 44001, USA
jneuhoff@wooster.edu
http://jneuhoff.com
doi:10.1017/S0140525X22000425, e144
Abstract
Sex/gender is a continuous variable that researchers frequently
treat as dichotomous. This practice can mask continuous under-
lying adaptive traits and yield spurious dichotomous “sex differ-
ences.”As such, many sex differences in self-protection may be
evolutionary by-products of underlying adaptations rather than
adaptations themselves. Binary analysis of continuous sex/gen-
der is ill-considered science that can contribute to inequality
and counterproductive public policy.
It’s a convenient shorthand to treat sex/gender as dichotomous,
and Benenson et al. necessarily rely on studies that use this short-
hand exclusively. However, it’s important to emphasize that sex/
gender is, in fact, a multifaceted bimodal continuous variable.
The authors have done outstanding work synthesizing copious
cross-cultural data, unequivocally demonstrating stronger self-
protective reactions in females. However, whether these differ-
ences are truly a “series of evolved female adaptations”that con-
stitute an adaptive survival strategy, or a collection of adaptations
and evolutionary by-products remains in question.
Are all sex differences adaptations? Sex differences in a psycho-
logical trait can serve as supporting evidence for an evolved psycho-
logical mechanism. However, sex differences are neither necessary
nor sufficient to identify a psychological adaptation or differentiate
a purported adaptation from an evolutionary by-product (an evolved
trait inexorably linked with an adaptation). It’slikelythatsomeof
Benenson et al.’s proposed female self-protection adaptations have
continuous factors other than sex underlying the “sex differences”
and that some of these differences are (either functionless or
fitness-enhancing) evolutionary by-products of these underlying
factors.
For example, Benenson et al. note that women “overestimate
the speed of incoming stimuli”more than men (sect. 7.1).
Commentary/Benenson et al.: Self‐protection as an adaptive female strategy 49
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
Auditory perception research shows that both sexes perceive
incoming sound sources as faster and closer than equivalent
receding sounds and as arriving sooner than they actually do
(Neuhoff, 2001,2016; Neuhoff, Planisek, & Seifritz, 2009). This
“auditory looming bias”is an adaptation that provides a margin
of safety and affords more time than expected to prepare for a
threat’s arrival (Neuhoff, 1998). Women exhibit a larger bias
than men and are therefore afforded greater self-protection
(Neuhoff, Hamilton, Gittleson, & Mejia, 2014; Neuhoff et al.,
2009; Schiff & Oldak, 1990). If we stop there, we have a story
that fits nicely with “self-protection as an adaptive female
strategy.”
However, subsequent work showed that physical strength is
correlated with the looming bias. The more formidable one is,
the smaller the bias (Neuhoff, Long, & Worthington, 2012).
Importantly, this relationship persists even when within-sex cor-
relations are calculated. Thus, strength is more important than
biological sex in explaining reactions to looming sounds. The
sex difference is simply a by-product of a mean sex difference
in strength, indicating vulnerability to threat. Sample sizes in
these looming studies are not as large as those in the work
reviewed by Benenson et al., and this sex difference was not
included in their analysis. Nonetheless, other sex differences in
self-protection may also be by-products of a more explanatory
continuous variable.
For example, Benenson et al. identify sex differences in pain as
a female self-protective adaptation. However, men and women
also differ in sex hormone levels. Although the effects of estrogen
and testosterone on pain perception are complex, there is ample
evidence showing that under many conditions, testosterone
decreases responses to pain, while estrogen increases it (Craft,
2007; Flake, Hermanstyne, & Gold, 2006; Ji, Hu, Li, & Traub,
2018; Ji, Tang, & Traub, 2008; Lesnak, Inoue, Lima, Rasmussen,
& Sluka, 2020; Schertzinger, Wesson-Sides, Parkitny, &
Younger, 2018). In animal models, ablation of estrogen receptors
eliminates sex differences in pain entirely (Li et al., 2009). In
humans, testosterone therapy successfully relieves fibromyalgia
pain (Dubick, Ravin, Michel, & Morrisette, 2015; White et al.,
2015).
Thus, reproductive hormones (whose main evolutionary job is
facilitating reproduction) can plausibly explain sex differences in
pain perception. This hypothesis is buttressed by data showing lit-
tle evidence of sex differences in pain among children (Boerner,
Birnie, Caes, Schinkel, & Chambers, 2014). Importantly, these
pain–hormone relationships are robust within-sex (Ivkovic, Racic,
Lecic, Bozovic, & Kulic, 2018;Katoetal.,2020). The dichotomous
shorthand that we use for “sex”obscures the bimodal yet continuous
underlying potential cause of the “sex difference.”
Rather than an adaptation, sex differences in pain may be an
exaptation of the effects of reproductive hormones. Variability
in sex hormones may indeed currently enhance female fitness
in response to pain. However, the main adaptive problem sex hor-
mones solved was facilitating sexual reproduction. This reasoning
applies to many of Benenson et al.’s other proposed female self-
protection adaptations that are influenced by hormones, includ-
ing immune function, fear, stress, autoimmune disorders,
responses to vaccines, depression, anxiety, and emotion recogni-
tion (Amiaz & Seidman, 2008; Dirlikov, Lavoie, & Shem, 2019;
Glover et al., 2013; Hermans, Putman, Baas, Koppeschaar, &
van Honk, 2006; Maeng & Milad, 2015; Rehbein et al., 2021;
Rosen, Ham, & Mogil, 2017; Ruggieri, Anticoli, D’Ambrosio,
Giordani, & Viora, 2016). Underlying continuous factors might
also explain responses to some social threats. For example, sex dif-
ferences in smiling may be explained by variability in dominance
and affiliation, as even within-sex variability in smiling predicts
physical dominance (Hess, Adams, & Kleck, 2005; Ketelaar
et al., 2012; Kraus & Chen, 2013).
Abraham Maslow famously said, “If all you have is a hammer,
everything looks like a nail.”This quote perfectly encapsulates the
current state of research on sex differences. Benenson et al.
acknowledge the dubious wisdom of treating sex/gender as binary,
but it was the only type of data available for their synthesis.
Historically, researchers (myself included) have failed to treat sex/
gender as continuous. Thus, the only analysis tool currently avail-
able is a “binary hammer”that destroys the nuance of the contin-
uum and masks other potentially more explanatory constructs.
As scientists, we need to do better to examine sex/gender as a
multifaceted continuous variable because it’s good science and it
has critical implications for equality and public policy.
Dichotomizing continuous variables obscures individual differ-
ences and nonlinear relationships, underestimates effect size,
reduces statistical power, and decreases reliability (MacCallum,
Zhang, Preacher, & Rucker, 2002). This mismeasurement leads
to poor policy recommendations and greater inequality. For
example, in a startling commentary on Campbell’s(1999) original
“staying alive”target article, which posited greater female self-
protective behaviors in risk-taking and aggression, Browne
(1999) concluded that perhaps women were not fit to serve in
military combat or as business executives. Clearly, looking at con-
tinuous data through a dichotomous lens misses a richer explana-
tion of the phenomena (Cameron & Stinson, 2019).
Acknowledgments. I am grateful to Bryan Karazsia and Laura Sirot for their
cogent comments.
Financial support. This research received no specific grant from any fund-
ing agency, commercial, or not-for-profit sectors.
Conflict of interest. None.
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The pregnancy compensation
hypothesis, not the staying alive
theory, accounts for
disparate autoimmune functioning of
women around the world
Erin M. O’Mara Kunza, Jackson A. Goodnighta
and Melissa A. Wilsonb
a
Department of Psychology, University of Dayton, Dayton, OH 45469, USA and
b
School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA
ekunz1@udayton.edu
jgoodnight1@udayton.edu
mwilsons@asu.edu
https://sites.google.com/udayton.edu/erinomarakunz
www.sexchrlab.org
doi:10.1017/S0140525X22000589, e145
Abstract
The pregnancy compensation hypothesis provides a mechanistic
explanation for the evolution of sex differences in immune sys-
tem functioning, the excess of women experiencing autoimmune
disease, and why this is observed only in industrialized nations;
none of which can be explained by the staying alive theory, as
proposed by the authors of the target article.
In the target article, self-protection as an adaptive female strategy
(Benenson et al., this issue), the authors extend the staying alive
theory (SAT; Campbell, 1999) to be a global theory explaining
sex differences in physiology and genetics, and gender differences
in culture, without describing mechanisms for how each of these
could have evolved under the SAT, nor whether these observa-
tions are also consistent with other theories. In particular, we
take issue with the supposition that sex differences in immune
function are explained by the SAT. In contrast, the pregnancy
compensation hypothesis (Natri, Garcia, Buetow, Trumble, &
Wilson, 2019) provides mechanistic explanations for the evolution
of sex differences in immune function and differences in industrial-
ized and non-industrialized nations. We explain our critiques below.
First, sex differences in immune function are rampant in
industrialized populations, with approximately 80% of autoim-
mune diseases occurring in women. In general, women are nine
times more likely than men to develop autoimmune diseases
(Ngo, 2014). For example, women have a higher rate than men
for rheumatoid arthritis with a 7:1 female to male ratio
(National Institute of Arthritis and Musculoskeletal and Skin
Disease, 2019) and Alzheimer’s disease with a 2.3:1 female to
male ratio (Mouton et al., 2018). While there are autoimmune
diseases in which men have a higher incidence rate than
women (e.g., ankylosing spondylitis; Jørgensen, Pedersen,
Commentary/Benenson et al.: Self‐protection as an adaptive female strategy 51
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
Nielsen, Jacobsen, & Frisch, 2012), these are less common in the
population. Thus, there are many more autoimmune diseases
with a higher incidence in women and there are many more
women affected by these diseases than men.
Importantly, the sex difference in autoimmune disease has
not been observed in non-industrialized populations, which
are more likely to represent an ancestral disease condition. In
fact, autoimmune diseases, in general, are less prevalent in non-
industrialized countries (Adebajo, 1997;Clark,Al-Yaman,
Cowden, & Rockett, 1996; Strachan, 1989). The SAT cannot
explain why autoimmune diseases are present (and show a
female bias) in industrialized populations but not non-
industrialized populations. Unlike the SAT, the pregnancy com-
pensation hypothesis (Natri et al., 2019) can explain the differ-
ences in the incidence of autoimmune diseases for women in
industrial versus non-industrialized nations. The pregnancy
compensation hypothesis (Natri et al., 2019) suggests that differ-
ences in the prevalence of autoimmune diseases between indus-
trialized and non-industrialized populations are because of
ancestral women’s immune system evolving to expect to fre-
quently, and shortly after puberty, host a genetically distinct pla-
centa and fetus during pregnancy without rejecting it, while
simultaneously protecting the mother from pathogens and par-
asites. In the absence of frequent pregnancy, or by postponing
pregnancy well beyond puberty, women’simmunesystemsare
proposed to experience dysregulation, with the resources that
would be directed at tolerating a placenta and fetus redirected
such that the immune system attacks healthy tissue.
Ancestral women were more likely to give birth closer to the
onset of puberty than women are today, but even today women
in industrialized nations have a longer delay between menarche
and first pregnancy than women in non-industrialized nations.
In 2019, the adolescent fertility rate in the United States and
the United Kingdom was 17 and 12 per 1,000 women, respectively
(United Nations Population Division, 2021), whereas it was 155
per 1,000 in Chad, 180 in Niger, and 165 in Mali (The World
Bank, 2022), three of the least developed countries in the world
(United Nations Conference on Trade and Development, 2022).
Further, in the United States, the average age of a women’s first
pregnancy in 2014 was 26 years old, up from 21 years old in
1972 (Mathews & Hamilton, 2016), which is older than women
in non-industrialized nations, like Bangladesh (Bongaarts &
Blanc, 2015), and Niger (Pariona, 2017) where the average age
of first pregnancy is about 18 years old, and among the
Tsimane Amerindians of Bolivia, where the average age of first
pregnancy is 18 (Gurven, 2012).
Second, counter to the SAT, in industrialized populations
where there is evidence of a higher immune response in women
than men, autoimmune disease results in significantly higher
morbidity in women with autoimmune diseases, and even higher
mortality in women than men (as in the case of Alzheimer’s dis-
ease). The authors argue that heightened risk for autoimmune
disorders observed among women is consistent with SAT, in
that this is one expression of women’s heightened reaction to
physical threats. This argument is aligned with the health-survival
paradox, also described in the paper, which states that the greater
incidence of illness and severity of physical symptoms is offset by
the survival enhancing benefits of a strengthened (if overly active)
immune response. However, the argument that a greater preva-
lence of autoimmune disorders supports greater reproductive
fitness among women rests on the assumption that autoimmune
disorders do not reduce women’s fertility. Yet, it is widely
acknowledged that autoimmune disorders are associated with
an increased risk for miscarriage (Gleicher, Weghofer, &
Barad, 2012), and there is also evidence to suggest that autoim-
mune disorders reduce fecundity among women, two outcomes
that would reduce reproductive fitness. Moreover, autoimmunity
is associated with elevated risk for numerous infertility-linked
disorders, including endometriosis, premature ovarian failure,
and polycystic ovary syndrome, among other conditions (as
reviewed by Haller-Kikkatalo, Salumets, & Uibo, 2012). Thus,
while it may be true that enhanced survival after reproductive
age could increase reproductive fitness by providing opportuni-
ties for caregiving investments to be made in older adulthood,
reductions in reproductive fitness owing to increased suscepti-
bility to autoimmune disorders would likely outweigh these
benefits.
In sum, if the SAT was an evolved process for women, as
explained and extended in the target article, it would not differen-
tially impact women based on whether they are in an industrialized
versus non-industrialized nation and it would not negatively impact
the reproductive success of women through the increased incidence
of autoimmune diseases. The sex differences in immune function,
the significant increase in autoimmune diseases in women in
industrialized populations, and the unique evolution of the sex
chromosomes, instead, can all be explained by the pregnancy com-
pensation hypothesis (Natri et al., 2019).
Financial support. Melissa A. Wilson was supported by R35GM124827.
Conflict of interest. None.
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The “staying alive”theory reinforces
stereotypes and shows women’s
lower quality of life
Konrad Szocika,b
a
Interdisciplinary Center for Bioethics, Institution for Social and Policy Studies,
Yale University, New Haven, CT 06511, USA and
b
Department of Social Sciences,
University of Information Technology and Management in Rzeszow, 35–225
Rzeszow, Poland
konrad.szocik@yale.edu
doi:10.1017/S0140525X22000395, e146
Abstract
Staying alive theory explains why women have more effective
self-protective mechanisms in terms of woman’s role as a
mother and caregiver. This theory reinforces stereotypes and
the relationship of oppression and submission to men.
Somewhat paradoxically, it also points to women’s lower quality
of life, which may be explained by their greater fear of threats
caused by men’s power.
The “staying alive”theory (SAT) has the potential to reinforce ste-
reotypes, not erase them, contrary to what the authors suggest. It
preserves old-fashioned notions about women and ties them to
their supposed subordination to raising children. If we take the
perspective of a feminist philosophy that assumes that certain psy-
chological and behavioral traits that we more often attribute to
women have social rather than biological roots (Mikkola, 2017),
the SAT then becomes an example of essentialist thinking about
women that we should move away from. After all, it may be
that women exhibit certain behaviors more frequently solely
because they have been forced to do so as a result of centuries
of oppression and domination by men (women as victims of vio-
lence, rape, exploitation, abuse by men [the problem of power,
oppression, and discrimination in feminist ethics, see
Lindemann, 2019]). Thus, an unjust social arrangement has gen-
erated the regularities described by SAT. The SAT excludes this
possibility by equating the woman with the mother at the starting
point.
Needless to say, this theory completely excludes not only the
dynamics of homosexual couples –if we already want to remain
in these exclusionary structures based on the category of relation-
ship –but all persons other than men and women. The SAT rein-
forces the stereotypical role of women as caretaker mothers,
emphasizing the importance of a woman’s survival rate for raising
offspring. This supposed biological regularity is the reason for the
exploitation of millions of women around the world not only in
the domestic and family circle, but also as caregivers in various
areas of social life. Gender is reinforced and constituted through
the repetition of gender-coded acts (Butler, 1990).
Essentialism is also evident in the philosophy of biology
adopted here, which seems to assume sex differences between
men and women as fundamental, fixed differences that determine
the described patterns of behavior different for both sexes
(Weaver & Fehr, 2017). The association of men with risky and
aggressive behaviors and women with caring, aloof, and cautious
behaviors may promote the reinforcement of stereotypes. An
example of a stereotypical attitude is the very fact that the research
and analysis are directed at inter-gender differences and the very
identification of “woman”as a special, separate research category,
as if it were implicitly assumed that the category “woman”is sep-
arate from the category “man”and as such, must lead to separate
conclusions, because it is probably also governed by separate laws
inherent only in this category. And what is the reason for the dis-
tinctiveness of these categories and the differences in the laws
governing them? From differences in biology.
Although the authors cite the so-called “trauma hypothesis”as
a potential alternative explanation, they reject it because, in their
view, the veracity of this hypothesis should suggest the existence
of stronger self-protective mechanisms in men than in women.
Feminist ethics, however, points out that while men may indeed
be at greater risk of death and injury from risky behavior or par-
ticipation in conflict, it was men, not women, who for centuries
created and developed the model of dominance and power that
prevails to this day and which favors men over women. The start-
ing point for drawing conclusions should therefore not be lethal
threats, but the exploitation and subordination of women to
men as the real source of self-defense mechanisms. These are
incomparable types of risks.
The women’s research methodology assumed by the SAT
assumes a dominance relationship, or at least creates the illusion
that women function within an environment that is the result of
structures based on a dominance relationship (Weaver & Fehr,
2017).
It is also worth noting another SAT conclusion that is as par-
adoxical as it is alarming. Women have greater chances of survival
and longer life expectancy, but lower quality of life by more often
experiencing fear and pain, as well as more often finding them-
selves in social roles that cause discomfort. This conclusion,
while arguably correct from a biological, medical, and psycholog-
ical perspective, surprisingly conflicts with a philosophical tradi-
tion that emphasizes the importance of well-being, the so-called
life worth living. The SAT shows that women inherently have
lives less worth living than men, a paradoxical adaptation as
long as we value quality of life rather than existence itself. This
seemingly more advantageous situation for men as measured by
a higher degree of well-being can be compared to Parfit’s
(1984) famous thought experiment about hypothetical future
humans who live a life worth living for 40 years, then die as a
result of radioactive waste stored by an earlier generation. But
before they die, they do quite well.
It can be assumed that women’s lower quality of life (living in
constant stress and fear of men’s aggression, threat of rape, exploi-
tation, exclusion that makes it difficult to obtain satisfying social
roles, hence more frequent depression and suicide attempts)
results precisely from centuries of oppression and domination
Commentary/Benenson et al.: Self‐protection as an adaptive female strategy 53
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
by men, and thus from a pathological social system. From this point
of view, longer survival becomes a dubious advantage, further rein-
forcing the dominant position of men, who are freed from the pos-
sible “duty”of caring for offspring by longer-lived women who live
longer precisely to care for offspring. This reinforces the feminist
diagnosis of social relations in which men, even if they live shorter
lives, simply enjoy life more than women who are constantly con-
cerned about themselves and their offspring. The authors do not
explain causation, but references to similar regularities in other spe-
cies suggest that they recognize a biological, rather than environ-
mental, determination of regularities such as greater concern for
offspring in females than in males.
In sum, the SAT contains too many references to biological
determinants, overemphasizes a woman’s biological role as
mother, and exposes a woman’s greater responsibility and con-
cern for her offspring. All of these are precisely the contexts in
which women have traditionally been entangled and which are
often used to justify the exploitation and subordination of
women in their traditional roles as mothers and caregivers.
Financial support. The work on this text was written under the Bekker
Fellowship (3rd edition) funded by the National Agency for Academic
Exchange (Decision No. PPN/BEK/2020/1/00012/DEC/1) for a research stay
at Yale University (USA) in the academic year 2021/2022.
Conflict of interest. None.
References
Butler, J. (1990). Gender trouble: Feminism and the subversion of identity. Routledge.
Lindemann, H. (2019). An invitation to feminist ethics. Oxford University Press.
Mikkola, M. (2017). Gender essentialism and anti-essentialism. In A. Garry, S. J. Khader
& A. Stone (Eds.), The Routledge companion to feminist philosophy ( pp. 168–179).
Routledge, Taylor & Francis Group.
Parfit, D. (1984). Reasons and persons. Clarendon Press.
Weaver, S., and Fehr, C. (2017). Values, practices, and metaphysical assumptions
in the biological sciences. In A. Garry, S. J. Khader & A. Stone (Eds.), The
Routledge companion to feminist philosophy (pp. 314–327). Routledge, Taylor &
Francis Group.
Psychological and behavioral
implications of self-protection and
self-enhancement
Dianne M. Ticea, Roy F. Baumeisterb
and Constantine Sedikidesc
a
Department of Psychology, Brigham Young University, Provo, UT 84602, USA;
b
School of Psychology, University of Queensland, St. Lucia, Brisbane, QLD 4072,
Australia and
c
Department of Psychology, University of Southampton,
Southampton SO17 1BJ, UK
diannetice@byu.edu
r.baumeister@uq.edu.au
c.sedikides@soton.ac.uk
doi:10.1017/S0140525X22000632, e147
Abstract
Self-protection can have psychological and behavioral implications.
We contrast them with the implications of a self-enhancement
strategy. Both self-enhancement and self-protection have costs and
benefits as survival strategies, and we identify some of the
emotional, cognitive, and behavioral tradeoffs associated with the
differential preferences for each strategy. New analyses on a large
existing data set confirm the target article’s hypothesis that
women are more attuned than men to potential negative
consequences of innovations.
Benenson et al. (this issue) did a commendable job of establishing
self-protection as a general biological strategy that women adopt
and of elucidating the strategy’s health benefits (and occasional
costs). They had less space for discussing behavioral implications.
We assume the behavioral benefits are easy to understand, but are
there hidden costs? These could indicate vulnerabilities or prob-
lems that could afflict women.
Some of our own work has explored tradeoffs between self-
protection and self-enhancement (Alicke & Sedikides, 2009;
Baumeister, Tice, & Hutton, 1989; Tice, 1991). Self-protection is
centrally about avoiding risk. But great achievements often require
risk, indeed sometimes substantial risks. A self-protective orienta-
tion can prevent disastrous failures –but may well also prevent
breakthrough successes. Arguably, throughout the history of civ-
ilization, men have been responsible for the majority of both,
likely driven in part by the male quest for self-enhancement.
The self-protective element of female psychology may be a reason
for this gender disparity.
Self-enhancement, on the other hand, is centrally about taking
risks. Self-enhancement facilitates achievement (Sedikides, 2020).
It is positively related to or increases the pursuit and attainment of
personally important goals, while augmenting creativity. And it is
linked to seeking leadership positions and being elected as a
leader.
By coincidence, one of us recently participated in an investiga-
tion in which participants predicted the consequences of various
hypothetical innovations (e.g., a robot to chop down trees, a pro-
cedure for cloning house pets) on a scale from −100 (mostly neg-
ative) to +100 (mostly positive) (Reece, Eubanks, Liebscher, &
Baumeister, 2022). Gender was not in the study design, but demo-
graphic data were collected, thereby enabling exploratory post hoc
reanalyses. Across all studies and conditions (N= 1,567), the male
mean of 25.0 was much more positive than the female mean of
0.75. The male confidence interval was far above the neutral mid-
point (zero) whereas the female confidence interval included it.
Put another way, exploratory reanalyses of an existing data set
found that men predicted more positive than negative conse-
quences whereas women predicted equal amounts of both.
Thus, consistent with Benenson et al.’s (this issue) theory, the
potential downside of various innovations was more salient to
the women than the men.
Self-enhancement has also implications for psychological
health. It is associated with, predicts, and increases self-esteem
(Sedikides, Gaertner, & Cai, 2015). In addition, it is positively
associated with, and predicts, high levels of life satisfaction or pos-
itive affect, and low levels of negative affect or depression (Dufner,
Gebauer, Sedikides, & Denissen, 2019). Moreover, self-
enhancement increases life satisfaction and subjective well-being,
and decreases depression, anxiety, and stress (O’Mara, Gaertner,
Sedikides, Zhou, & Liu, 2012). These benefits of self-enhancement
are observed across cultures.
54 Commentary/Benenson et al.: Self‐protection as an adaptive female strategy
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
Women report lower levels of self-enhancement (Grijalva
et al., 2015) and self-esteem (Kling, Hyde, Showers, & Buswell,
1999). Further, women report lower life satisfaction and more
negative affect than men, while the evidence on positive affect is
inconclusive (Batz-Barbarich, Tay, Kuykendall, & Cheung,
2018). Average happiness levels across female populations are
likely reduced by their considerably higher incidence of depres-
sion (Salk, Hyde, & Abramson, 2017). Benenson et al. (this
issue) note the link between female self-protection and depression
but do not offer much explanation other than the heightened sen-
sitivity to pain. There may be multiple links, including the lesser
use of self-enhancement.
Another traditional theme of gender theory is the tradeoff
between agency and communion (Bakan, 1966), with women
being less agentic but more communal than men (Hsu, Badura,
Newman, & Speach, 2021). This too fits well into the self-
protection analysis. Agency means taking initiative, which brings
risk. Communion means connecting with others, which is vital
for safety. The female self-protective orientation would plausibly
contribute to a shift in their psychology toward greater commu-
nion rather than agency. Again, the benefits from such a shift
are clear, but the lesser agency might carry costs such as lesser
achievement or innovation.
A related pattern emerges from clinical observations. People
adopt self-protective patterns or schemas during difficult child-
hood or adolescent periods, and then sometimes maintain these
in adult relationships. These schemas have high predictive value
by repeating the same feelings or experiences over and over
again. If men engage in this practice, women engage in it more
(Shorey et al., 2012). These schemas generate high levels of nega-
tive affect and self-defeating consequences, and go against self-
enhancement (Young, Klosko, & Weishaar, 2003).
In closing, we concur with Benenson et al.’s (this issue) power-
fully integrative idea that women tend to adopt self-protection as
a general strategy. This strategy has certain advantages, which
could be complemented by a trade-off with a self-enhancement
strategy.
Financial support. The authors declare the received no outside financial
support for this work.
Conflict of interest. The authors declare no financial interest.
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Women amid the COVID-19
pandemic: Self-protection through
the behavioral immune system
Alfonso Troisi
Department of Systems Medicine, University of Rome Tor Vergata, 00133 Rome,
Italy
alfonso.troisi@uniroma2.it
http://medschool.uniroma2.it/2016/05/31/alfonso-troisi/
doi:10.1017/S0140525X22000413, e148
Abstract
Studies of the activation of the behavioral immune system trig-
gered by the coronavirus disease-2019 pandemic have demon-
strated that evolutionary explanations of individual differences
in self-protection should not be based only on parental invest-
ment and sexual selection theory. An evolutionary model must
also incorporate individual differences that arise within each
sex as a result of life history strategies and attachment patterns.
The coronavirus disease-2019 pandemic presents a unique oppor-
tunity to test the evolutionary hypothesis that women show stron-
ger self-protective reactions than men to environmental threats. In
their target article, Benenson et al. focus mainly on sex differences
in COVID-19 mortality rates and the activation of the physiolog-
ical immune system. Their argument can be expanded by analyz-
ing sex differences in the activation of the behavioral immune
system and women’s emotional reactions to the risk of
COVID-19 infection.
The physiological immune defense is merely reactive because it
is triggered only after the infection has occurred within the body.
Schaller (2011) has convincingly demonstrated that selection
Commentary/Benenson et al.: Self‐protection as an adaptive female strategy 55
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
pressures have reinforced our defenses against infections by caus-
ing the evolution of a behavioral immune system that is separate
from, and complementary to, the physiological immune system.
The behavioral immune system includes a set of proactive mech-
anisms that inhibit contact with pathogens in the first place. These
mechanisms offer a sort of psychological and behavioral prophy-
laxis against infection. The two emotional and interrelated reac-
tions associated with the activation of the behavioral immune
system are fear of infection and pathogen disgust sensitivity
(Troisi, 2020). Based on the evolutionary hypothesis of sex differ-
ences in self-protection, the COVID-19 pandemic is expected to
have caused more intense fear of infection and pathogen disgust
sensitivity in women than in men.
Data on fear of infection support the evolutionary hypothe-
sis. A recent scoping review based on 14 studies conducted in
different populations showed that female gender was the most
consistent predictor of fear of COVID-19 (Quadros, Garg,
Ranjan, Vijayasarathi, & Mamun, 2021). Compared to studies
focusing on fear of infection, reports on sex differences in dis-
gust sensitivity are fewer but their findings are anyway consis-
tent with evolutionary predictions. Using a large nationwide
Chinesesample,Ding,Yang,Ji,andGuo(2021)foundthat
the COVID-19 outbreak increased levels of pathogen disgust
sensitivity more in women than in men. In a large sample of
Australian university students, Stevenson, Saluja, and Case
(2021) found that the increase in disgust sensitivity observed
during the COVID-19 pandemic was significantly greater in
women than in men.
The COVID-19 outbreak is a natural experiment that not only
confirms the existence of sex differences in self-protective reac-
tions to environmental threats but also enriches our understand-
ing of their evolutionary-developmental origin. Studies of the
activation of the behavioral immune system triggered by the
COVID-19 pandemic have demonstrated that evolutionary expla-
nations of individual differences in self-protection should not be
based only on parental investment and sexual selection theory, as
Benenson et al. have done in their target article. A comprehensive
evolutionary model of greater or lower levels of self-protection
must also incorporate the individual differences that arise within
each sex as a result of life history strategies and attachment
patterns.
Life history theory is a mid-level evolutionary framework
that explains individual differences in a variety of interrelated
phenotypic traits including physiology, psychology, and behav-
ior. At the core of the life history theory is the appreciation for
the long-lasting influence of ecological information acquired in
early development being utilized as a forecast in service of
meeting the environmental demands of later development.
Individual variation in life history strategies (i.e., different pat-
terns of allocation of finite time and energy budgets
between competing activities) can be arranged along a contin-
uum, from “fast”to “slow”(Del Giudice, 2009). In terms of psy-
chological attitudes and behaviors related to self-protection,
slow strategists are characterized by higher levels of harm avoid-
ance and risk averseness. Fast strategists are characterized by the
opposite pattern, showing higher propensity toward impulsiv-
ity, short-term planning, and risk taking. Using an online sur-
veytool,Corpuz,D’Alessandro, Adeyemo, Jankowski, and
Kandalaft (2020) found that, among 209 U.S. adult participants
interviewed during the first wave of the COVID-19 pandemic,
life history orientation predicted endorsement of precautionary
measures. Compared to fast strategists, slow strategists endorsed
higher levels of self-protection (e.g., wearing a mask or to
stay-at-home).
The attachment system is an important psychological mecha-
nism that bridges the gap between early exposure to environ-
mental harshness and/or unpredictability and life-history
strategies enacted in adulthood (Szepsenwol & Simpson, 2019).
Different attachment patterns (secure, preoccupied, fearful, avoi-
dant) exert major effects on emotion regulation and, therefore,
they are likely to impact individual attitudes toward self-
protection. In line with such a prediction, in a sample of 101
Italian healthcare workers employed in a COVID-19 university
hospital, Troisi, Croce Nanni, Riconi, Carola, and Di Cave
(2021) found that participants with higher levels of fearful attach-
ment reported more intense fear of infection.
Interestingly, neither the study by Corpuz et al. (2020) nor the
study by Troisi et al. (2021) found significant relationships
between sex and the dependent variables reflecting individual atti-
tudes toward self-protection. These findings do not necessarily
mean that the evolutionary hypothesis advanced by Benenson
et al. in their target article is invalid. Rather, they suggest the
necessity of integrating the predictions derived by asymmetrical
parental investment and sexual selection theory with those
based on life history theory and attachment models. Given its
importance for survival and biological adaptation, the evolution
of the behavioral immune system is likely to have been shaped
by multiple selection pressures. A comprehensive understanding
of the psychological and behavioral defenses against infection
requires a conceptual framework that integrates different evolu-
tionary subtheories: parental investment, sexual selection, life his-
tory strategies, and attachment orientations. The COVID-19
outbreak offers a unique opportunity to apply such an integrated
framework to the study of self-protective behavior.
Financial support. This research received no specific grant from any fund-
ing agency, commercial, or not-for-profit sectors.
Conflict of interest. None.
References
Corpuz, R., D’Alessandro, S., Adeyemo, J., Jankowski, N., & Kandalaft, K. (2020). Life his-
tory orientation predicts COVID-19 precautions and projected behaviors. Frontiers in
Psychology,11, 1857. https://doi.org/10.3389/fpsyg.2020.01857
Del Giudice M. (2009). Sex, attachment, and the development of reproductive strategies.
The Behavioral and Brain Sciences,32(1), 1–67. https://doi.org/10.1017/
S0140525X09000016
Ding, Y., Yang, J., Ji, T., & Guo, Y. (2021). Women suffered more emotional and life
distress than men during the COVID-19 pandemic: The role of pathogen disgust
sensitivity. International Journal of Environmental Research and Public Health,
18(16), 8539. https://doi.org/10.3390/ijerph18168539
Quadros, S., Garg, S., Ranjan, R., Vijayasarathi, G., & Mamun, M. A. (2021). Fear of
COVID 19 infection across different cohorts: A scoping review. Frontiers in
Psychiatry,12, 708430. https://doi.org/10.3389/fpsyt.2021.708430
Schaller M. (2011). The behavioural immune system and the psychology of human social-
ity. Philosophical transactions of the Royal Society of London. Series B, Biological
Sciences,366(1583), 3418–3426. https://doi.org/10.1098/rstb.2011.0029
Stevenson, R. J., Saluja, S., & Case, T. I. (2021). The impact of the COVID-19 pandemic
on disgust sensitivity. Frontiers in Psychology,11, 600761. https://doi.org/10.3389/
fpsyg.2020.600761
Szepsenwol, O., & Simpson, J. A. (2019). Attachment within life history theory: An evo-
lutionary perspective on individual differences in attachment. Current Opinion in
Psychology,25,65–70. https://doi.org/10.1016/j.copsyc.2018.03.005
Troisi A. (2020). Fear of COVID-19: Insights from evolutionary behavioral science.
Clinical Neuropsychiatry,17(2), 72–75. https://doi.org/10.36131/CN20200207
Troisi, A., Croce Nanni, R., Riconi, A., Carola, V., & Di Cave, D. (2021). Fear of
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56 Commentary/Benenson et al.: Self‐protection as an adaptive female strategy
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
Pathological complexity and the
evolution of sex differences
Walter Veitaand Heather Browningb
a
School of History and Philosophy of Science, The University of Sydney, Sydney,
NSW 2006, Australia and
b
London School of Economics and Political Science,
Centre for Philosophy of Natural and Social Science, London WC2A 2AE, UK
wrwveit@gmail.com
DrHeatherBrowning@gmail.com
https://walterveit.com/
https://www.heatherbrowning.net/
doi:10.1017/S0140525X22000498, e149
Abstract
Benenson et al. provide a compelling case for treating greater
investment into self-protection among females as an adaptive
strategy. Here, we wish to expand their proposed adaptive expla-
nation by placing it squarely in modern state-based and behav-
ioural life-history theory, drawing on Veit’spathological
complexity framework. This allows us to make sense of alterna-
tive “lifestyle”strategies, rather than pathologizing them.
Benenson, Webb, and Wrangham (2022) provide an excellent
empirical synthesis of data from different fields to support the
idea that a greater investment into self-protection has evolved as
a unique adaptive strategy in females. They draw on data that pro-
vide varying levels of support for the hypothesis that human
females do produce stronger self-protective reactions than
males, to a range of threats, which then suggests the presence of
a general female self-protection strategy that may be adaptive
rather than pathological. Nevertheless, the question then remains
as to how best explain the results, and identify the adaptive func-
tion of domain-general self-protective behaviour. The authors
locate this within Campbell’s“staying alive”theory: That
human females have a higher fitness value arising from self-
protection than males do.
Here, we wish to expand their proposal by placing it squarely
in modern state-based and behavioural life-history theory, which
–despite a brief mention –was surprisingly not discussed within
the target article. Life-history theory originated in simple models
representing the necessity of a trade-off between longevity and the
number of offspring created in a particular breeding period to
maximize fitness (Stearns, 1992). Even this restricted approach
to modelling life histories has demonstrated that greater offspring
care leads to an investment into survival, rather than reproductive
output (Hamilton, 1966; Williams, 1966). While Benenson et al.
mention this part of the literature, they do not draw on the sub-
sequent extension of this early work, which proceeded through
the inclusion of behaviour and varying bodily states, to eventually
lead to state-based behavioural and life-history theory
(McNamara & Houston, 1996). This theory is not only important
to understand the ecological lifestyles of different species, but also
to assess the teleonomic complexity of different organisms in
achieving their goal of reproduction –or rather, fitness-
maximization –as it is only within such an ecological theory of
the organism that we can distinguish pathological traits and
behaviours from adaptive ones.
It is for this reason that one of us has used the term “patholog-
ical complexity”to refer to the complexity of this set of trade-offs,
that is, the number of parameters and constraints in the teleo-
nomic optimization problem, studied by modern state-based
behavioural and life-history theory (see Veit, 2022a,2022b).
The term “pathological”here is not meant to imply that life-
history complexity is inherently pathological; but rather that it
is only in assessing this complexity of optimizing trade-offs to
maximize fitness that we can determine which behaviours are
pathological. This can be done by calculating the trade-offs inher-
ent to different life-history strategies, with fitness serving as the
common currency of organismal design, which a common exam-
ple within life-history theory will help to illustrate. In Australian
marsupials of the genus Antechinus, males typically die after a sin-
gle breeding season. While such behaviour in males may be seen
as strikingly pathological, through life-history theory we can see
that it is not. Their best response to their species-specific patho-
logical complexity is to invest all their resources into reproduction
in a single breeding season, and hence this is not pathological.
Some life-history strategies will have higher pathological
complexity than others, due to the higher number of parameters
and constraints in their environment and evolutionary design.
Again, this does not make their responses pathological, but it
makes their design a more complex trade-off problem to be
solved. If a life-history strategy puts all efforts into reproduction
in a single period, there will inevitably be fewer complex trade-
offs to be solved. Indeed, pathological complexity can be
increased through external factors (e.g., the presence of preda-
tors) or internal ones (e.g., the need for a greater variety of
nutrients), as well as the availability of more degrees of freedom
of behaviour, which can greatly increase the computational
problem of maximizing fitness both for the organism and for
those modelling their life-history strategies. If we fail to account
for one of those factors in our models, we will inevitably come
to re-examine mistaken evaluations of some behaviours as path-
ological when we gain a greater understanding of species- and
sex-specific life-history strategies.
It is thus hardly surprising that we urge the use of life-history
theory in answering the question of whether females have a dif-
ferent optimal design solution to deal with their particular
pathological complexity arising from the trade-off between
survival and reproduction. It is the framework to assess the
adaptive nature of diverse female traits and to challenge
prevailing ideas about the pathological nature of differences
between the sexes. In order to evaluate whether self-protection
is sex-specific, life-history strategy requires investigation into
the different social and ecological niches faced by human
males and females, both currently and throughout our adaptive
history, to identify possible factors –or sets of factors –that
could serve to explain the observed difference in behaviour.
For instance, it is possible that females face a greater range of
potential threats to survival and reproduction, and hence
require a more complex adaptive behavioural phenotype in
response. If survival is more important for females than it is
for human males, this may well suggest that their life-history
complexity is higher with more threats to keep track of –
demanding unique and more risk-averse adaptations, just as
the authors suggest.
Finally, we applaud the application of this work, in demon-
strating that the distinctive female responses to threat are an
adaptive reaction to their differential niche, and should thus
not be pathologized. For too long, deviations from the male
Commentary/Benenson et al.: Self‐protection as an adaptive female strategy 57
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
“norm”have been seen as problematic, rather than simply dif-
ferent acceptable strategies. As the authors suggest, this can
enhance understanding of female health and well-being with
reference to what is normal for this group. Experiences and
conditions that are more common in females –such as pain
disorders, anxiety, and autoimmune diseases –can be exam-
ined and treated accordingly. A deeper understanding of the
environmental challenges that have shaped these sex differ-
ences, and where they currently still do or do not apply,
could also assist in determining when there is a normal reac-
tion or a pathological maladaptation to modern social and liv-
ing conditions.
Financial support. WV’s research was supported under Australian Research
Council’s Discovery Projects funding scheme (project number FL170100160).
Conflict of interest. The authors have no conflicts of interest to report.
References
Benenson, J. F., Webb, C. E., & Wrangham, R. W. (2022). Self-protection as an adaptive
female strategy. Behavioral and Brain Sciences,1–86. https://doi.org/10.1017/
S0140525X21002417
Hamilton, W. D. (1966). The moulding of senescence by natural selection. Journal of
Theoretical Biology,12(1), 12–45.
McNamara, J. M., & Houston, A. I. (1996). State-dependent life histories. Nature 380
(6571), 215–221.
Stearns, S. C. (1992). The evolution of life histories. Oxford University Press.
Veit, W. (2022a). Consciousness, complexity, and evolution. Behavioral and Brain
Sciences,45(E61), 47–49.
Veit, W. (2022b). Health, Agency, and the Evolution of Consciousness. Ph.D. thesis,
University of Sydney. Manuscript in preparation.
Williams, G. C. (1966). Natural selection, the costs of reproduction, and a refinement of
Lack’s principle. The American Naturalist,100(916), 687–690.
Sex differences in longevity are
relative, not independent
Mikkel Wallentin
Department of Linguistics, Cognitive Science and Semiotics, Aarhus University,
8000 Aarhus C, Denmark
mikkel@cc.au.dk
https://pure.au.dk/portal/en/persons/mikkel-wallentin(abf0a704-afc4-4576-
9df7-3d84420bc2fc).html
doi:10.1017/S0140525X22000401, e150
Abstract
I ask three questions related to the claims made within the stay-
ing alive theory (SAT): Is survival more fitness-enhancing for
females than for males? Does the historical record on sex differ-
ences in mortality support the SAT? Is it possible to talk about
“independent selective pressures on both male and female traits”
when all we have are sex/gender comparisons?
A central tenet of the target paper is that “survival is more
fitness-enhancing for females than for males.”There is something
odd about this claim, since survival is a necessary condition for
reproductive fitness. Without survival there is no reproduction.
Without further specification it thus becomes meaningless to
talk about sex-differences in fitness linked to survival. A favorable
reading of the paper says that the authors are really aiming not at
survival but longevity. In other words: survival beyond a certain
point. One crucial time point is obviously mating. Before mating
survival is infinitely fitness-enhancing for both sexes.
Beyond mating, the mother’s reproductive fitness relies on her
survival during pregnancy as well and this is where the paths of
the two sexes diverge. The fitness of the father no longer depends
on his own survival, but solely on the survival of the mother and
the fetus. One may therefore argue that after this time point there
is a stronger evolutionary pressure on the survival of the mother
than on the father. After the child is born, the reproductive fitness
of both parents depends on the survival of the child. The authors
convincingly argue that mothers spend more time than fathers
looking after their children and that her survival thus may be
more important for the survival of the child than that of the
father. This seems to be the evolutionary account behind females’
longer life expectancies, according to the staying alive theory
(SAT). However, it misses one crucial point. Males are fertile
throughout their lives, and their fitness is not tied to one individ-
ual pregnancy. It is therefore difficult to see why longevity would
not also increase male fitness equally, given that longer life would
provide opportunities for additional mating. Data exist to support
a correlation between parity (i.e., reproductive fitness) and lon-
gevity in both sexes (Barclay & Kolk, 2019; McArdle et al.,
2006). Within this naive evolutionary framework for human
reproduction, which disregards culture, family, and parental col-
laboration, longevity thus appears to be an advantage for both
sexes. More effort is needed to flesh out why the evolutionary
advantage of longevity would be greater for females than for
males.
Does the historical record on sex differences in mortality sup-
port the SAT? Following the link to parental care, the authors pre-
dict “increased magnitudes of sex differences following puberty.”
However, when making a detailed investigation of differences in
mortality, the picture is not clear. Excess male deaths in reproduc-
tive years (between 15 and 40), where the evolutionary pressure
would occur according to the SAT, account for less than 25% of
the life expectancy gap, both presently and historically (Zarulli,
Kashnitsky, & Vaupel, 2021). The sex difference in life expectancy
is also to some extent a recent phenomenon (Beltrán-Sánchez,
Finch, & Crimmins, 2015; Thorslund, Wastesson, Agahi,
Lagergren, & Parker, 2013; Wilmoth, 2007). The growth of the
gap in mortality in the twentieth century (Fig. 1) can to a large
extent be explained by differences in smoking habits (Preston &
Wang, 2006) and lung cancer is still one of the most significant
predictors of sex differences in age of death (main article,
Fig. 2). However, historically, most excess male death occurred
during the pre-mating stage of life (0–14 years) (Zarulli et al.,
2021), with infant deaths carrying the majority of the burden
(Fig. 1). Doesn’t both the historical variability of sex/gender differ-
ences in life expectancy and the changing distribution of excess
deaths in males across age-spans yield an explanatory challenge
for the SAT which proposes that the difference is due to an inde-
pendently adapted female trait linked to “parental investment”?
Furthermore, is it possible to talk about “Independent selec-
tive pressures on both male and female traits”when all we have
are sex/gender comparisons? The claim in SAT that lower levels
of aggression forms “a positive female adaptation driven by the
critical importance of the mother’ssurvivalforherownrepro-
ductive success”(Campbell, 1999) has an important flaw. If less
is more, then having nothing may be even better. One could
argue that not having antlers or peacock feathers are positive
58 Commentary/Benenson et al.: Self‐protection as an adaptive female strategy
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
female adaptations. There is an infinite list of such adaptive lack
of properties within this type of logic. It is therefore vital to
focus on actual positive attributes and behaviors. This, however,
rests on the assumption of independence. In the conclusion, the
authors state that “independent consideration of each sex, along
separate dimensions, is necessary for understanding the ways in
which each sex’s traits are optimized.”Specific male traits are
argued to include: “direct competition, physical aggression,
risk-taking, showing off, impulsivity, sensation-seeking, and
resource accumulation.”The SAT, on the other hand, advocates
that “females more than males evolved to avoid physical aggres-
sion.”It is not difficult to see that this is just a reversal of what is
reported as a male adaptation. The critical claim “that lower
rates of aggression by women reflect not just the absence of
male risk-taking but are part of a positive female adaptation”
remains untested and perhaps untestable in a binary compari-
son between males and females with only one effective degree
of freedom. Thus, in the conclusion the authors state that
“Had the evidence existed, we would have compared the repro-
ductive success of females who varied in their degree of reac-
tions to threats, and not included males at all.”Are the
authors willing to stick their neck out and hypothesize that
females who adhere to the description in their paper, that is,
are more pain sensitive, who wake up at night, are more fearful
and neurotic, also live longer and have greater reproductive suc-
cess than females who do not? If so, would one end of the spec-
trum be less female than the other? Would that make the
outcome independent?
Financial support. This study was supported by Independent Research Fund
Denmark grant 0132-00081B.
Conflict of interest. The author has no conflicts of interest to declare.
References
Barclay, K., & Kolk, M. (2019). Parity and mortality: An examination of different explan-
atory mechanisms using data on biological and adoptive parents. European Journal of
Population,35(1), 63–85. doi: 10.1007/s10680-018-9469-1
Beltrán-Sánchez, H., Finch, C. E., & Crimmins, E. M. (2015). Twentieth century surge of
excess adult male mortality. Proceedings of the National Academy of Sciences,112(29),
8993. doi: 10.1073/pnas.1421942112
Campbell, A. (1999). Staying alive: Evolution, culture, and women’s intrasexual aggres-
sion. Behavioral and Brain Sciences,22(2), 203–214. doi: 10.1017/S0140525X99001818
McArdle, P. F., Pollin, T. I., O’Connell, J. R., Sorkin, J. D., Agarwala, R., Schäffer, A. A., …
Mitchell, B. D. (2006). Does having children extend life span? A genealogical study of
parity and longevity in the Amish. Journals of Gerontology. Series A: Biological Sciences
and Medical Sciences,61(2), 190–195. doi: 10.1093/gerona/61.2.190
mortality.org. Human Mortality Database. Retrieved 2021/12/21, from University of
California, Berkeley (USA), and Max Planck Institute for Demographic Research
(Germany).
Preston, S. H., & Wang, H. (2006). Sex mortality differences in The United States: The
role of cohort smoking patterns. Demography,43(4), 631–646. doi: 10.1353/dem.
2006.0037
Thorslund, M., Wastesson, J. W., Agahi, N., Lagergren, M., & Parker, M. G. (2013). The
rise and fall of women’s advantage: A comparison of national trends in life expectancy
at age 65 years. European Journal of Ageing,10(4), 271–277. doi: 10.1007/
s10433-013-0274-8
Wilmoth, J. R. (2007). Human longevity in a historical perspective. In P. S. Timiras (Ed.),
Physiological basis of aging and geriatrics (4th ed., pp. 11–22). Informa.
Zarulli, V., Kashnitsky, I., & Vaupel, J. W. (2021). Death rates at specific life stages mold
the sex gap in life expectancy. Proceedings of the National Academy of Sciences,118
(20), e2010588118. doi: 10.1073/pnas.2010588118
Authors’Response
Females undergo selection too
Joyce F. Benenson , Christine E. Webb
and Richard W. Wrangham
Department of Human Evolutionary Biology, Harvard University, Cambridge,
MA 02138, USA
Joyce.Benenson@gmail.com
doi:10.1017/S0140525X22000644, e151
Abstract
Extending Campbell’s (1999) staying alive theory (SAT) beyond
aggression, we reviewed evidence that females are more self-pro-
tective than males. Many commentators provided additional
supporting data. Sex differences in life-history adaptations, in
the optimal relation between survival and reproduction, and in
the mechanisms underlying trade-offs involved with self-protec-
tion remain important topics with numerous opportunities for
improved understanding.
Figure 1 (Wallentin). Differences in average age of death
across time (moving average 5 years) when including or dis-
counting infant deaths. The difference in life expectancy has
varied through history, and much can been explained by dif-
ferences in infant mortality. Data from Sweden, adapted
from the Human Mortality Database (mortality.org).
Response/Benenson et al.: Self‐protection as an adaptive female strategy 59
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
We very much appreciate the thoughtfulness and insights of the
commentators. A number of commentators contributed novel
evidence and ideas that expanded staying alive theory (SAT)
and provided new directions for future research. Others ques-
tioned whether sex differences exist in the value of survival for fit-
ness. A third group believes that the evolution of male mate
competition rather than any female adaptations for longevity
explain sex differences in self-protectiveness. Finally, a few ques-
tioned whether a biological/evolutionary basis for sex differences
is a viable or useful consideration in analyses of human beings.
We consider each of these in turn.
R1. Additional evidence and future directions
Both Hawkes and Veit and Browning expand SAT by using life-
history theory to understand whether females approach the trade-
off between survival and reproduction differently than males do.
Much of Campbell’s SAT and our extension of it is derived from
or consistent with Hawkes’research demonstrating that women
enhance the reproductive success of both their offspring and
their grandchildren. While a former idea that only males can ben-
efit by extending their reproductive careers into old age is there-
fore wrong, Hawkes nevertheless emphasizes that precisely how
the reproductive strategies of each sex are expected to differ
remains a complex problem. Her analyses of the trade-offs
between survival and reproductive success for each sex provide
avenues for future research, including in terms of understanding
residual reproductive value, mating sex ratios, birth spacing, and
grandmothering.
We appreciate Veit and Browning’s focus on the importance
of carefully weighing whether commonly occurring, cross-
culturally present patterns of behavior, such as those we have
identified in girls and women, should be dubbed “pathological.”
What looks pathological from one perspective may be adaptive
from another. Veit and Browning suggest that further research
is needed to investigate whether compared to males, females
face more threats, find modern life more difficult, or need to
live longer to be reproductively successful. We have focused on
the latter as a reason for females’greater reactions to threat.
Nonetheless, we fully concur that more focus on the details of
females’and males’life histories and the components that may
maximize reproductive success (RS) for each sex are necessary
in order to distinguish pathology from normality.
Bleske-Rechek and Deaner add the important insight that cul-
tures often prioritize the survival of females over males. Their evi-
dence is compelling that in times of disasters, in the military, or in
dangerous jobs more generally, females’lives are prized over
males’lives at least in many western, educated, industrialized,
rich, and democratic (WEIRD) societies. Furthermore, women
are more likely than men to be perceived as victims and female
victims generate more sympathy than male victims. Their evi-
dence added to the SAT suggests that a biological basis for
females’greater self-protectiveness is complemented by wide-
spread social norms stipulating that females merit greater protec-
tion than males. Further investigation across non-WEIRD
cultures could help verify the universality of this norm.
The coronavirus disease-2019 (COVID-19) data presented by
Troisi perfectly fit the predictions of SAT. Referring to the impor-
tance of the behavioral immune system, Troisi presents evidence
that women are more fearful than men of contracting
COVID-19 and exhibit a larger increase than men in disgust sen-
sitivity to pathogens. Nevertheless, he argues, and we agree, that
many other factors besides sex are important in determining
how the behavioral immune system functions. Two factors in par-
ticular, slow versus fast life histories and fearful versus not fearful
attachment patterns, were shown by Troisi to affect the behavioral
immune system’s reactions to COVID-19. Although those factors
were unrelated to sex, it would be interesting to investigate
whether more males than females opt for a faster life history
(Del Giudice, 2009) or begin life with disorganized/fearful attach-
ments (Carlson, Cicchetti, Barnett, & Braunwald, 1989) as some
have suggested, which could influence the interaction between
sex and these variables.
We appreciate the evidence that Tice, Baumeister, and
Sedikides (Tice et al.) provide from a re-analysis of their data
that elegantly fits predictions from SAT. Their results show that
females are much less enthusiastic than males about potentially
dangerous hypothetical new inventions, such as a tree-chopping
robot or a pet cloner. They concur that females are more self-
protective than males, but they add that this can entail costs.
Specifically, they hypothesize that greater self-protectiveness
reduces self-enhancement, which is associated with greater life
satisfaction, higher self-esteem, more positive affect, and lower
levels of anxiety and depression. Thus, they postulate that anxiety
and depression in particular can be multi-determined, caused by
both extreme forms of self-protection and/or reduced levels of
self-enhancement. Worldwide however, no evidence shows that
females exhibit lower life-satisfaction or less positive affect than
males, and if anything females appear more positive (Bem,
1974; Lucas & Gohm, 2000). Furthermore, cross-culturally sex
differences in anxiety and depression along with many of the
other self-protective characteristics we have described, such as
insomnia, smiling, or neuroticism, emerge or are accentuated
in puberty. It seems unlikely that sex differences in self-
enhancement suddenly emerge in puberty. Nonetheless, we con-
cur that self-protection likely inflicts costs as Tice et al. propose,
which may be related to reduced self-enhancement depending
on its definition in a particular culture. SAT posits that for
females the costs of self-protection are outweighed by the benefits
of enhanced survival of themselves and their descendants.
March and Gaertner distinguish between detection of and
reaction to visual threat. We appreciate their re-analysis of their
data to show that females exhibit stronger reactions than males
specifically to threatening stimuli as would be predicted by SAT.
What females do not exhibit however is faster detection of threat
which also would be expected by SAT. This disparity is intriguing
and warrants further investigation. One possibility is that it
depends on sex differences in visual acuity. Although the cause
is not genetic, myopia is twice as prevalent in white and East
Asian females as males by late adolescence according to a large
meta-analysis (Rudnicka et al., 2016). In contrast, much evidence
supports the lower threshold of females than males for detecting
varied types of auditory, olfactory, and tactile stimuli (Velle,
1987). Further research is necessary to examine whether females
would detect threatening stimuli more rapidly than males using
other sensory modalities.
Cassar adds to our conceptualization of the social relations
that would be predicted by SAT. She suggests that reducing com-
petition benefits females not only through harm avoidance and
protection of relationships but also by facilitating future coopera-
tion. Her thesis is that cross-culturally females tend to display
more egalitarian behavior than males in order to buttress recipro-
cal relationships with unrelated females and asymmetrical
relations with higher-ranked mates. By insisting on equality,
60 Response/Benenson et al.: Self‐protection as an adaptive female strategy
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
females signal that they are not planning to compete directly
against another female or a mate. Nonetheless, as Cassar has
shown, females will compete under some contexts, such as in sup-
port of their own children or on others’behalf, ways of competi-
tion that may be acceptable to unrelated females and a mate.
Emphasizing equality or competition for acceptable outcomes
therefore reduces threat, which would be in line with SAT.
Crosby, Hahnel-Peeters, and Buss (Crosby et al.) and
McDonald and James note that we omitted processes directly
related to females’and males’unique concerns about reproduc-
tion. Thus, morbidity or mortality related to childbirth, gestation,
and lactation; female or male reproductive organs; and sexuality
were excluded. Our purpose was to compare processes that
could threaten females and males to the same extent.
As Crosby et al. highlight, sex differences in self-protective
behavior would be even greater if some of these were included.
The examples they provide demonstrate this convincingly. For
instance, one of the largest sex differences occurs for sexual dis-
gust (see also Sparks, Fessler, Chan, Ashokkumar, & Holbrook,
2018). Crosby et al. make the compelling argument that this pro-
tects women from sub-optimal mates and sexually transmitted
diseases. Likewise, both McDonald and James and Crosby et al.
emphasize that fear of rape is one major reason for women’s self-
protective behaviors. McDonald and James go even further and
suggest that threats to survival and to reproductive choice are con-
flated for women and should be distinguished, especially for the
social behaviors we describe. We are unsure how they could be
disentangled as they are not necessarily mutually exclusive. For
instance, rape can co-occur with murder. Furthermore, if fear of
rape were the sole reason for the greater self-protective social
behaviors exhibited by females than males, then self-protective
social behaviors and neuroticism would be unnecessary with
other women. This is not the case. Several of the self-protective
behaviors we described, including smiling, politeness, or identifi-
cation of emotions, are even stronger when girls and women
interact with same-sex peers than with their male counterparts.
Nevertheless, had we included all sex-biased concerns about
reproduction and sexuality, then some unique aspects of male
reproductive success, such as public displays of wealth, degree
of sexual motivation, or erectile function, would be more threat-
ening to males than females, unless these threatened females’
lives personally.
Archer and Fuentes suggest that SAT would be improved by
examining how self-protective characteristics co-vary and whether
they form a package. As Archer recommends, using multivariate
statistical analyses such as Mahalanobis’sDpermits examination
of covariation between the characteristics we identify. We expect
that covariance will be strong in human females, as many studies
already demonstrate positive associations between two or more of
the self-protective behaviors we have described including among
immune functioning, pain, sleep, social behaviors, neuroticism,
and emotional reactions to threat. If the disparate self-protective
reactions form a single package, this could motivate useful ideas
about underlying mechanisms.
Archer further asks how sexual selection theory and SAT fit
together. We accept that sexual selection theory, which typically
refers to male mate competition, is usefully redefined as natural
selection that includes each sex’s reproductive strategies
(Carranza, 2009). This permits male mating competition, female
self-protective behaviors, as well as many other sex-differentiated
strategies for survival and reproductive success to be categorized
under one overarching rubric (Clutton-Brock & Huchard, 2013;
Stockley & Bro-Jørgensen, 2011). As Aung, Baek, and Puts
(Aung et al.),Wallentin, and others recommend,
understanding of the ultimate and proximate mechanisms that
produce specific traits will be better illuminated after the differen-
tial forces that shape particular adaptations or groups of adapta-
tions are identified. Some of these will differ by sex.
R2. Is longevity more important to females’than males’
reproductive success?
Several commentators question our postulation that longevity is
more important to reproductive success for females than males,
including Brooks and Blake,Hagen, Knorr, Li, Mensing, and
Scelza (Hagen et al.), and Wallentin. Because theoretically only
males can reproduce until death, common wisdom holds that sur-
vival at late ages is less important for females than males. SAT is
constructed on the opposite premise, that extended survival is
more important for the reproductive success of females than
males. This analysis relies heavily on Hawkes and others’research
on the importance of grandmothering (Campbell, 1999;Hawkes
et al., 1997; Sear & Mace, 2008). Lacking the input for a mathe-
matical or game theoretic model, we present several assumptions
that support our premise.
First, all women benefit reproductively from staying alive long
enough to invest in both children (especially daughters) and
grandchildren (Daly & Perry, 2021; Hawkes et al., 1997; Sear &
Mace, 2008). Second, men’s fighting power (Daly & Wilson,
1988), fluid cognitive abilities (Salthouse, 1996), and fertility
decline with age (Matsumoto, 2002; Santiago, Silva, Alves,
Oliveira, & Fardilha, 2019), thereby reducing many elements
that contribute to male mating success. Thus, in a contemporary
study of over 330 million births across 17 rich European nations,
where men live longer than in poorer areas, “age-specific fertility
rates of men quickly decline to very low levels above age 45”
(Dudel & Klüsener, 2021, p. 424). Ages 20–45 years were men’s
maximum reproductive years and at most 0.2% of men became
fathers after age 59 years. Therefore, despite the extended repro-
ductive success of a few famous men (Betzig, 1986), relatively
few older men can amass enough resources to both outcompete
younger, stronger men and be attractive to younger, fertile
women. In contrast, despite large variation across 25 contempo-
rary Western nations in when grandparenthood begins (ages
47–60), a first grandchild is born when a grandmother is on aver-
age 51 years and a grandfather is 54 years (Leopold & Skopek,
2015). Mortality in this sample is 83 years for women and 78
years for men, so that grandparenting can in theory extend for
decades following the end of fertility. In a separate analysis of
12 contemporary European nations with over 36,000 grandpar-
ents older than 50 years and a grandchild younger than 13
years, grandmothers were more than twice as likely as grandfa-
thers to provide frequent care to their biological grandchildren
(Daly & Perry, 2021). Furthermore, when they helped, grandfa-
thers invested as much in non-biological children as biological
children. The mean age of grandmothers was 63 years (range
50–96 years) and grandfathers 65 years (range 50–100 years).
Thus, while a few older men, particularly in polygynous societies,
greatly increase their reproductive success until the end of their
lives at the expense of younger men’s reproductive success,
most men in monogamous societies follow a similar reproductive
age trajectory as women albeit beginning and ending a few years
later. Furthermore, it seems unlikely that this should differ in sub-
sistence societies where lifespan tends to be shorter.
Response/Benenson et al.: Self‐protection as an adaptive female strategy 61
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
Brooks and Blake provide several important theoretical rea-
sons why more research is necessary to understand the relation
between survival and reproductive success, especially for human
females and males. They cite the aphorism that applies to many
taxa that males “live fast and die young”and elaborate on how
greater extrinsic mortality can act then to enhance mortality
from intrinsic causes. They then make an exception for humans
by suggesting that the greater survival of women over men may
be incidental. As examples, because women’s survival is traded
off against childbirth and childcare, which increase mortality,
reduced fertility in contemporary society may artificially increase
women’s survival. Alternatively, because amassing resources and
status takes time and increases reproductive success for men as
Hagen et al. also argue, selection for longevity may have
increased for males: Increased longevity in females would then
be a by-product. These are important questions, and we await
further evidence. Nonetheless, worldwide across natural fertility
populations in small scale societies, females live longer than
males (Ember & Ember, 2003). Precise supporting data exist
from Sweden from the 1700s (Allman, Rosin, Kumar, &
Hasenstaub, 1998) quantifying the sex difference as Wallentin
partially depicts in the graph he includes.
Hagen et al. concur that a mother is more important than a
father to a child’s survival. This might well explain what
Bleske-Rechek and Deaner emphasize: Cultures routinely prior-
itize survival of women over men. Nonetheless, paternal invest-
ment can enhance RS especially when women live with their
husbands’families or lack the support of female kin. Therefore,
women should select husbands who will provide extended assis-
tance or resources. Hagen et al. and Brooks and Blake argue
that men need time to acquire lots of resources to attract
women and outcompete same-age and younger men. Whether
this occurs routinely in primarily monogamous societies however
seems unlikely based on contemporary evidence, where women
prefer mates 2–3 years older than they are (Walter et al., 2020).
Thus, even though the average age of first reproduction has always
been higher for males than females across primate species (Bogin,
1999) and human females undergo menopause, we postulate that
on average, longevity is more important for females’than males’
reproductive success.
Nevertheless, we fully acknowledge that more empirical
research is required to examine the relation between longevity
and reproductive success for each sex as Brooks and Blake
recommend. A life history approach as endorsed by Hawkes,
Brooks and Blake, and Veit and Browning will help clarify the
trade-offs between reproduction and survival for females and
mating competition and survival for males. All other things
being equal, both women and men gain reproductive success
from living longer, but we suggest that the marginal value is
higher for women than men because of women’s greater invest-
ment in children and grandchildren.
R3. Females’greater longevity: Selection for survival or
incidental to males’mate competition?
Relatedly, another group of commentators argue that the sex dif-
ference in self-protectiveness results solely from a trade-off with
risk-taking. Aung et al. and Wallentin are explicit that females
are more self-protective than males only because males’greater
mate competition prevents males from being maximally self-
protective, not because of any specialized evolutionary adapta-
tions unique to or extended in females. Likewise, in a paper of
which we were formerly unaware that presents a theory and evi-
dence that resembles our target article in many ways by Sparks
et al. (2018), males’risk-taking is presented as the reason why
females are more self-protective.
Campbell argued specifically against this proposition, and we
quoted her statement in our target article “that lower rates of
aggression by women reflect not just the absence of male risk-
taking but are part of a positive female adaptation driven by the
critical importance of the mother’s survival for her own reproduc-
tive success”(p. 204). We extended Campbell’s(1999)SATto
examine further evidence that females exhibit many adaptations
that protect them from threats. Our primary point is that
women who have stronger immune systems, faster withdrawal
responses to potentially injurious stimuli, more awareness of
nighttime and general environmental adverse forces, greater
avoidance of social threats, and a healthy degree of worry and
sense of vulnerability would live longer than those women who
did not have these reactions, and that this would be beneficial
in terms of fitness. As we described, evidence exists for
female nonhumans and humans that self-protectiveness, includ-
ing immunological, pain threshold, sleep cycles, and behavioral
conflict avoidance, is regulated by estrogens. More generally,
those individuals who respond more self-protectively to any
threat will generally survive longer, and females do so more
than males. If these reactions become too extreme, they become
maladaptive, and they may carry costs as Tice et al. point out,
but on balance, self-protective reactions prolong life. Critically,
SAT emphasizes that females’self-protectiveness does not arise
as an incidental result of males’risky mating strategies. Instead,
females have evolved mechanisms that have allowed them to pro-
long their lives. As previously emphasized, sex differences in mor-
tality at all ages are well-supported by the graph Wallentin
includes from the Human Mortality Database. Infant deaths per-
fectly track deaths that do not include infants. Sex differences also
clearly vary over time, but they are always present even in Sweden
in the 1700s (Allman et al., 1998).
Wallentin further wonders what evidence indicates that it is
caregiving that accounts for the benefits of greater self-
protectiveness in females. Across eight species of nonhuman pri-
mates, the ratio of female to male care of offspring is positively
associated with the ratio of female:male lifespan to the point
that in the callitrichid Callimico, which has particularly extensive
care by males, lifespans show no detectable sex difference (Allman
et al., 1998). This example illustrates the wider point about sex
differences in adaptation that we take from Campbell (1999). In
species in which male–male competition is relatively worthwhile,
investment in adaptations for competition is more beneficial for
males than investment in longevity. Males’longevity is therefore
reduced. For the females of those species, however, investment
in longevity yields positive adaptive benefits. The relatively
extended lifespans of females thus reflect both the absence of
the trade-off faced by males and the high value of long-term sur-
vival for females.
R4. Sex is not a useful construct for understanding
self-protectiveness
A final group of commentators do not believe sex contributes to
understanding self-protective behaviors. In the first sub-group,
Lin, Cuijpers, and Li (Lin et al.),Humeny, and Eagly suggest
that in some cases women are not more self-protective than
men, thereby challenging the validity of SAT.
62 Response/Benenson et al.: Self‐protection as an adaptive female strategy
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
Lin et al. raise two important examples of women’s appearing
less self-protective than men: Burnout in response to difficulties
with work–life balance and depression surrounding the birth of
a child. We suggest that these challenges are more specific to or
pronounced in women than in men, as with concerns raised by
Crosby et al. and McDonald and James. Consequently, compar-
isons with men are not equivalent. Lin et al.’s examples depend on
women’s taking primary responsibility for raising children and
thus being more affected by burnout and childbirth. For example,
in a meta-analysis of reasons for female and male physicians’
burnout, amount of workload, number of hours required, night-
time shifts, schedule inflexibility, and lack of supportive relation-
ships were some of the primary reasons for burnout (Azam,
Khan, & Alam, 2017). Too many work demands obviously are
more detrimental to primary than secondary caregivers. In
turn, the causes of perinatal depression have not been well iden-
tified, with both physiological responses to pregnancy and lack of
social support commonly cited (Eastwood, Kemp, & Jalaludin,
2015). Nonetheless, bearing primary responsibility for the sur-
vival of oneself and a newborn and possibly other children and
family members, especially when difficulties arise, would seem
to necessitate strong responses. Newer theories view these types
of strong responses as ways of social bargaining (Hagen &
Thornhill, 2017; Syme, Garfield, & Hagen, 2016). Recent evidence
suggests that when single fathers assume full responsibility for
childcare, they are three times more likely to die than partnered
fathers or single mothers (Chiu et al., 2018). SAT would predict
that women would respond more rapidly than men to reduce
threats whether by leaving an overwhelming job faster or procur-
ing assistance with child-rearing under difficult circumstances.
Humeny describes women who are victims of intimate partner
violence as not being self-protective. Again, this predicament is
not equivalent for the two sexes. Being a victim of intimate part-
ner violence is more common and more lethal for women because
they are less physically strong as we noted in our target article. As
Humeny adds however, being isolated from others and alone with
an abusive partner can make it very difficult for a woman to be
self-protective. In particular, attempts to leave a violent partner
may be less self-protective than remaining with him. Thus,
women may be choosing the most self-protective behavior avail-
able by staying with an abusive partner, especially if no one else
will protect them. We find it difficult to view severe victimization
from which there is little escape as evidence against women’s
motivation to protect themselves, despite the fact that abuse
inflicts serious physical and emotional damage.
Eagly provides three further important examples in which
women are less likely than men to protect themselves. First,
women more than men donate their kidneys, which incurs risk.
Second, more single German women than single men protected
Jews during the holocaust. Third, more women than men join
the Peace Corps which often entails traveling to and living in
areas with greater health risks. We agree that these examples
raise important questions that merit consideration. For instance,
how many of the organ donations are to kin? And when
women take explicit risks, what are their male counterparts
doing? As Eagly notes, women have always been less likely than
men to enter life-threatening professions from fighting fires, to
policing, to responding to natural disasters, as well as engaging
in social conflicts including the military, showing off, driving
recklessly, and so forth. Thus, it is plausible that during the holo-
caust, for example, men engaged in even more dangerous enter-
prises than women. Accepting Eagly’s data however, all else
being equal, SAT predicts that these women who purposefully
place themselves in danger by definition would have a lower prob-
ability of survival and reproductive success than women who
choose not to engage in dangerous activities and thus would rep-
resent exceptions. Without knowing the specific circumstances of
each woman who purposefully endangered her life however, it is
also possible that the costs she experienced were outweighed by
the benefits she accrued, in terms of establishing or maintaining
relationships, or self-enhancement as Tice et al. propose.
O’Mara Kunz, Goodnight, and Wilson (O’Mara Kunz et al.)
are concerned that the evidence we presented on autoimmune
diseases (ADs) is misleading. According to O’Mara Kunz et al.,
outside of industrialized societies ADs rarely occur and are not
more prevalent in females than males. Consequently, they believe
that ADs can be better explained by the pregnancy compensation
hypothesis than as maladaptive overly strong self-protective
immune responses. O’Mara Kunz et al. believe that ADs become
more common in industrialized societies because women spend
less time gestating and lactating and more time menstruating,
thereby changing their sex hormone profiles. This is an intriguing
proposition. However, even pre-pubertally more girls than boys
develop ADs although the sex bias is less pronounced than in
adults (Cattalini, Soliani, Caparello, & Cimaz, 2019). While
O’Mara Kunz et al.’s theory therefore can explain the large cross-
cultural differences in the prevalence of ADs, the generally
accepted understanding of ADs is that they constitute an overre-
action of the immune system and worldwide are more common in
women. Because threats differ across cultures, ADs may be a reac-
tion to only some types of immunological threats which may be
less present in non-industrialized societies.
Another sub-group, including Fuentes,Neuhoff,Huntsinger
and Raoul, and Szocik, do not believe sufficient evidence exists
to provide an evolutionary/biological explanation for the self-
protective processes we have identified. Specifically, Fuentes is
concerned that we neglect the nuances that occur across demo-
graphics and contexts. We acknowledge that the variability is
great and do not mean to downplay individual differences.
Troisi too was concerned that we neglected many individual dif-
ferences which also contribute to self-protective reactions.
Nevertheless, we do not agree with Fuentes that SAT is predicated
on the nuclear family as a basal human type. Rather, SAT is pred-
icated on the mother–child unit being universal, with female kin
and sometimes fathers and sons also participating in childcare
(Kramer, 2005; Wood & Eagly, 2002).
Neuhoff believes sex/gender is a continuous variable and that
considering it to be binary constitutes poor science and public
policy. We acknowledge in our target article that sex/gender is a
multidimensional construct and that the studies we found are
unfortunately limited by emphasizing binary comparisons.
However, we do not believe the complexity of the phenomenon
should preclude systematic investigations into biological and evo-
lutionary bases or explanations for sex differences.
Many characteristics associated with sex typically covary with
chromosomal sex, from the presence of internal and external
reproductive structures to sex-typed interests and activities, dis-
eases, gender roles, gender identity, sexual identity, and socializa-
tion received. Levels of sex hormones and physical strength
however are two characteristics strongly associated with sex chro-
mosomes and not simply by-products as Neuhoff asserts.
Within-sex variation in levels of sex hormones or physical
strength that correlate with degrees of self-protectiveness demon-
strates that different components of sex are related to self-
Response/Benenson et al.: Self‐protection as an adaptive female strategy 63
https://doi.org/10.1017/S0140525X21002417 Published online by Cambridge University Press
protectiveness. It does not negate the value of biological sex in
understanding self-protectiveness.
We consider it dangerous for scientific and practical reasons
not to acknowledge biological sex differences. Until recently, sex
has often not been considered to be an important variable in
medical research involving human or nonhuman species. The
assumption was that the results from male animals, including
men, would apply to female animals, including women. This
has led to inferior diagnostic and treatment tools for women,
causing untold numbers of girls’and women’s deaths
(McGregor, 2020). Until girls’and women’s lives are examined
objectively, and they are considered important in their own
right, this will not be remedied.
Nevertheless, our analysis in no way minimizes the importance
of understanding sex as a continuous variable. We fully acknowl-
edge that all individuals have some traits that are associated more
commonly with the other sex. Therefore, individuals should be
understood holistically and not categorized based on any single
factor.
Huntsinger and Raoul, similar to Neuhoff and Fuentes,do
not believe sufficient evidence exists to provide an evolutionary/
biological explanation for the diverse processes we have identified.
Instead, they believe the findings we present are based on stereo-
types. While we do not discount the potential role of this and
other social and environmental factors, we question whether sex-
biased stereotypes exist for the types of evidence we have
described. For example, women are less likely to die than men
at any age, but more likely to experience some illnesses and
chronic conditions. Does this make women less or more healthy
than men? Likewise regarding pain, women are typically cele-
brated for their endurance of pain given how difficult childbirth
can be, whereas men in turn are expected to withstand other
sorts of pain. What then are sex stereotypes regarding pain? We
are not aware of stereotypes regarding sleep, concern about the
environment, or fears of disease transmission. Along the same
lines, we think it premature to conclude that women categorically
“face more chronic strains and stressors”than men, and this is the
cause of sex differences in depression or anxiety. By what mea-
sures do women suffer more chronic stress than men? If they
do however, how can Huntsinger and Raoul then conclude that
“the emotional lives of women and men are nearly identical,”
when evidence points to sex differences in prevalence rates of
depression, anxiety, and many other concerns from sexual dys-
functions and paraphilias to eating disorders (Hartung & Lefler,
2019)?
Moreover, there is biological evidence for many of the sex dif-
ferences we describe. Although females frequently have been
excluded from human (McGregor, 2020) and nonhuman
(Clayton, 2016) studies, several studies of sex differences with
rodents indicate that compared with males, females exhibit stron-
ger immune responses to various pathogens and vaccines (Klein
& Flanagan, 2016); exhibit lower pain thresholds (Smith, 2019);
and experience more nighttime awakenings (Paul, Dugovic,
Turek, & Laposky, 2006; Swift et al., 2020). Likewise, across pri-
mate species, females more than males avoid serious social con-
flicts (Fedigan, 1982; Smuts, 1987).
Nevertheless, we believe that if a behavior is adaptive, then
socialization and biology should work together to reinforce it,
not counter one another, as Bleske-Rechek and Deaner suggest
for self-protectiveness. Thus, disentangling the effects of evolved
behaviors and environmental inputs constitutes a difficult task
that requires as much evidence as possible.
Finally, Szocik believes that our analysis could be “used to jus-
tify the exploitation and subordination of women in their tradi-
tional roles as mothers and caregivers.”Obviously, we did not
intend that outcome, but it is probably true that any evidence
of group differences can be used by one group to disparage
another. One response could be to abandon any research on sex
differences. We prefer the alternative strategy of understanding
the issue, and in this case showing how the evolutionarily signifi-
cant roles of women as mothers and caregivers illuminate the ulti-
mate and proximate forces that shape women’s lives. Harmful
gender stereotypes get perpetuated by discounting the role not
only of social factors but also of biological ones –leaving us to
compare female phenotypes to male reference points rather
than considering them as adaptive responses in their own right.
Szocik also believes that we have implied that “that women
inherently have lives less worth living than men.”This was not
our intention, and we strongly disagree with this conclusion.
Our paper showed that human females have a series of adapta-
tions that tend to differ from those of men in a consistent pattern.
We did not focus on men’s lives but had we done so, we would
have underscored the difficulties men confront. As examples,
boys and men die at every age from disease, accidents, interper-
sonal conflicts, and other traumatic events more than girls and
women do. Men are more likely than women to suffer from
addictions, sexual dysfunctions and paraphilias, conduct disor-
ders, attention-deficit hyperactivity disorder, autism, learning dis-
orders (Hartung & Lefler, 2019), and to commit suicide or take
such poor care of themselves that they end up dying (Case &
Deaton, 2020). Those facts mean we are not surprised by the find-
ing that we cited earlier, that life satisfaction is at least as high
among women as among men (Lucas & Gohm, 2000). But
whether women or men can be said to have lives less worth living
is a judgment that we see as another matter entirely, one that our
paper does not address.
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