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Divorce Patterns and the Male-to-Female Mortality Ratio: Is Midlife Crisis the Death of Men?

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Abstract

Beginning in infancy, males have a higher mortality rate than females– this sex-differentiated pattern holds across stages of life, but is exacerbated during years of peak courtship (adolescence and young adulthood), likely as a function of the fact that young males partake in risky behavior during courtship (Kruger & Nesse, 2007). The Male-to-Female Mortality Ratio (M:F MR) peaks at around age 25. The current analysis suggests that a drop in this ratio at this life stage may pertain to the fact that marriage occurs at about the age of 25 in modern Western societies and that married men have less of an evolutionary incentive than single men to participate in risky behavior. Past research (Kruger & Nesse, 2007) has found that the M:F MR increases slightly at around age 50. According to Kruger and Nesse (2006), this increase results partly from the fact that men at middle age are dying due to mainly internal causes, such as heart disease, which may result from prior risky behaviors during young adulthood (Kruger & Nesse, 2006); however, this explanation does not account for the fact that men at midlife also show an increase in mortality (relative to females) for external causes of death. Based on an analysis of divorce trends vis a vis M:F MR patterns, we propose that this increase in the M:F MR likely results, partly, from middle-aged, divorced men engaging in risky courtship behaviors that have physical costs.
UNDERGRADUATE AR
TI
C
LE
EvoS
Journal
:
The Journal of the Evolutionary Studies Consortium
Divorce Patterns and the Male-to-Female Mortality Ratio: Is
Midlife Crisis the Death of Men?
Laura L. Johnsen1
Amanda E. Guitar2
Glenn Geher3
1Anthropology, Binghamton University
2Anthropology, Binghamton University
3Psychology, SUNY New Paltz
AB
STR
AC
T
Beginning in infancy, males have a higher mortality rate than females this sex-
differentiated pattern holds across stages of life, but is exacerbated during years of
peak courtship (adolescence and young adulthood), likely as a function of the fact
that young males partake in risky behavior during courtship (Kruger & Nesse, 2007).
The Male-to-Female Mortality Ratio (M:F MR) peaks at around age 25. The current
analysis suggests that a drop in this ratio at this life stage may pertain to the fact that
marriage occurs at about the age of 25 in modern Western societies and that
married men have less of an evolutionary incentive than single men to participate in
risky behavior. Past research (Kruger & Nesse, 2007) has found that the M:F MR
increases slightly at around age 50. According to Kruger and Nesse (2006), this
increase results partly from the fact that men at middle age are dying due to mainly
internal causes, such as heart disease, which may result from prior risky behaviors
during young adulthood (Kruger & Nesse, 2006); however, this explanation does not
account for the fact that men at midlife also show an increase in mortality (relative to
females) for external causes of death. Based on an analysis of divorce trends vis a
vis M:F MR patterns, we propose that this increase in the M:F MR likely results,
partly, from middle-aged, divorced men engaging in risky courtship behaviors that
have physical costs.
K
EYWOR
D
S
Young Male Syndrome, Male-to-Female Mortality Ratio,
M:F MR, Marriage, Divorce
AUTHOR NOTE: Please direct correspondence to Laura Johnsen, Department of Anthropology, Binghamton
University, P.O. Box 6000 Binghamton, NY 13902-6000, E-mail: lauraljohnsen@gmail.com
EvoS Journal: The Journal of the Evolutionary Studies Consortium
ISSN: 1944-1932 -
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2014, Volume 6(2), pp. 33-41. -33-
Divorce and M:F MR
EvoS Journal: The Journal of the Evolutionary Studies Consortium
ISSN: 1944-1932 -
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ttp://evostudies.org/evos-journal/about-the-journal/
2015, Volume 6(2), pp. 33-41.
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Across all stages of the human lifespan, males have a higher mortality rate
than females. This sex-differentiated pattern is exacerbated during years of peak
courtship (adolescence and young adulthood), likely as a function of the fact that
young males partake in risky behavior during courtship (Kruger & Nesse, 2007).
Across the lifespan, the Male-to-Female Mortality Ratio (M:F MR) peaks at around
age 25 (Kruger & Nesse, 2007). From an evolutionary perspective, across most
species, males tend to engage in less parental investment and females are more
selective when choosing mates (Trivers, 1972). Based on the notion of sexual
selection (Darwin, 1871), animals within a single sex compete in various ways for
access to desirable mates of the other sex. This process, known as intrasexual
competition (see Kruger & Nesse 2006), often plays out in fierce male/male
competition during prime courtship years within a species.
In humans, a species that fits the patterns of low male parental investment
(see Trivers, 1972) and male/male competition in early adulthood (see Buss &
Schmitt, 1993), there is strong selective pressure for males to partake in aggressive
and risky behavior during adolescence and young adulthood since choosing a
risky strategy demonstrates fitness and is likely to lead to increased mating
opportunities with evolutionary benefits that counteract costs associated with risk
and aggressive behavior (Wilson & Daly, 1985). Males often compete for mates by
competing for catalysts of mating success such as social status (Kruger & Nesse,
2007). Males who achieve success in such a competitive context are more
attractive to potential mates (see Buss, 2003), and are, thus, more likely to achieve
reproductive success.
Courtship is Risky
Competition and courtship display mechanisms often include elements of risk,
which are oftentimes driven by aggressive behavior: two bucks butting heads clearly
explicates male/male competition that is both explicitly aggressive and risky (Betzig
1986). The winner of this kind of competition demonstrates fitness, which will most
likely lead to increased opportunities to mate with females, but the male must risk
potential injury or death in the process. Moreover, these courtship mechanisms are
not always aggressive in nature (see Geher & Miller, 2008; Miller, 2000). In various
species, humans included, displays designed to attract mates often include
aesthetic, visual, acoustic, and/or behavioral displays. However, even such non-
aggressive forms of displays have elements of physical risk associated with them.
A classic example of a non-violent behavior that may be considered risky is when
male peacocks show off their plumage (Betzig 1986; Zahavi, 1977, 2003). While
peacocks strut their plumage to display fitness, they concurrently put themselves in
danger as predators may well notice the colorful display. The peacock with the
brightest and most symmetrical plumage will receive more female attention, but he
also is most likely to be killed by a predator (Zahavi, 1977, 2003). These examples
illustrate how evolution is a process that encourages maximizing long-term benefits
against a landscape of survival and reproduction-inhibiting costs.
In sexually reproducing species in which parental investments costs are higher
for females, males invest more in courtship (Kruger & Nesse, 2007) and bear greater
courtship-related risks as a result. In such species, reproductive success is more
Divorce and M:F MR
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2015, Volume 6(2), pp. 33-41.
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variable for males than for females (Bateman, 1948) an empirical reality that drives
variability in within-sex competition. Simply: Males are more likely to be shut out of
mating (compared with females), so males are, thus, more motivated to compete for
mates and, as a fatal consequence of these, oftentimes, risky behaviors, males
are more likely to die as a result.
Courtship Patterns and Mate Deception among Middle-Aged Men
Research suggests that on average, heterosexual males of middle age prefer
women 5-15 years younger than themselves, while heterosexual women, on
average, prefer a man that is 3-10 years older than themselves (Kenrick & Keefe,
1992). If a male is age 40, this would mean that he would prefer a mate between
ages 25-35. If his mate of interest were on the younger end of the scale, age 25,
she would most likely prefer a mate between ages 28-35. This would mean that
the 40-year-old male would have to create different courtship tactics to overcome
the age difference. He would have to prove his mate of interest that he has
higher status, more access to resources, wealthier, and more physically fit than
his younger counterparts.
One way that the middle-aged male could convey that he is of higher mate
value than his younger competition, is through mate deception. Deceiving a mate
is a type of non-violent risky behavior because, if discovered, it can take the
deceiver out of the mating pool. If other potential mates find out about the
deception, they will be less likely to mate with the deceiver. In a society where
courtship does not necessarily have to take place face-to-face, deceiving a
potential mate is relatively easy. Males and females alike can lie about their age,
job, and physical appearance. In the example above, with the 40-year-old
middle-aged male who wants a 25-year-old female mate, he will have to compete
with males closer to her age group. He would have less of a motive to lie about
his resources (as he probably has a higher-paying job, a nicer home, and
generally more wealth than the average 28-year-old male), but be more motivated
to lie about his physical fitness and age. Poor physical fitness and older age are
indicators of poor genetic quality. If a potential mate, like the 25 year-old woman,
thought that the 40-year-old male had poor physical fitness she would probably
be less likely to mate with him.
To prevent older age and poor physical fitness from being a deterrent from a
future partner, males of middle age would probably be more likely to lie about
their age and fitness level compared to men of a younger age group or women of
the same age. Males in general are more likely to lie about their financial assets
(Buss, 2003; O’Sullivan, 2008). Lying about finances would indicate that the male
has access to fewer resources than he is telling his potential mate about. This
lying tactic would be beneficial to the male because the female would be more
inclined to mate with him (Buss, 2003; O’Sullivan, 2008). If men are more willing
to lie about financial resources to attract mates, then they might be more inclined
to lie about physical fitness. Stronger physical fitness is an indicator of good
genetic quality and health. Males of middle age might be more likely to lie about
their physical health compared to younger males or females because they may
feel threatened by younger males.
Divorce and M:F MR
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2015, Volume 6(2), pp. 33-41.
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As stated before, mate deception is a risky practice because it can severely
lessen the pool of potential mates. In a study about online dating, women, when
compared to men, were most disturbed by deception about the age of their
potential mate, specifically if the match lied about being younger than his actual
age (Stieger, Eichinger, & Honeder, 2009). If a potential mate kept repeating this
kind of behavior, he narrows his selection of females.
Aside from lying about physical traits, males in middle age may engage in
more risky behaviors to demonstrate that they are able to “keep up with their
younger counterparts. If they are successful in their risk taking, that would make
them more appealing to a younger potential partner. However, if they are
unsuccessful, this behavior could put middle-aged males at risk for injury or death
depending on the level of risk they participate in.
An Evolutionary Analysis of the M:F MR in Humans
Human males also participate in both violent and non-violent forms of
competition. Human males display markers of wealth and earning potential during
courtship (Buss & Schmitt, 1993), even if these displays are false and, thus,
deceptive in nature (Kruger, 2008). In fact, a great deal of converging evidence
suggests that males are, compared with females, relatively likely to lie about their
finances to impress a member of the opposite sex (Barnacz, Amati, Fenton,
Johnson, & Keenan, 2009). This pattern often leads to disagreements with other
males in competitions over status often leading to violent outcomes (Daly &
Wilson, 1985). In fact, violence tied to several facets of the mating domain seems
to be a predominantly male behavioral feature (Shackelford, Goetz, Buss, Euler,
& Hoier, 2005; Buss, 2006).
In a highly influential set of studies on the topic of male/male competition,
Kruger and Nesse (2006, 2007) analyzed large public data sets from the World
Health Organization to examine the M:F MR from an evolutionary perspective in
various cultures. These researchers found that the M:F MR is consistently biased
against males, in all cultures, at all stages of the lifespan. However, this pattern is
exacerbated during young adolescence, the prime courtship years.
In the United States, at around age 25, there is a noticeable decrease in the M:F
MR (Kruger & Nesse, 2006) a fact that essentially means that the gap between
males and females closes. Males older than this stage still may die (an obvious
risk at any point during the lifespan), but the rate at which they die becomes less
disproportionate from the rate at which females die. A proximate cause of this
change in the mortality ratio is likely due to marriage which occurs at about this
age. Marriage likely has the effect of reducing courtship and competition
resulting in less injury and death associated with such outcomes. In fact, married
males have been shown to be healthier than their non-married counterparts
(Kiecolt-Glaser & Newton, 2001)
According to Kruger and Nesse (2006), the M:F MR continues to decrease
steadily from about age 25 (M:F MR = 4) until around age 40, however, an
increase in mortality rates was found from age 40 until about age 50 for both
internal and external causes of death. Continuing a focus on male/male
competition in early adulthood, Kruger and Nesse (2006) argue that this peak is
the result of intense male/male competition during early adulthood. In making this
argument, the authors point to the fact that this peak is particularly pronounced for
Divorce and M:F MR
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2015, Volume 6(2), pp. 33-41.
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“internal causes” of death, such as heart disease, which may result from risky
behaviors, such as smoking, early in adulthood and which are only at this stage
manifesting their deleterious consequences (Kruger & Nesse, 2006).
While this interpretation of the data in terms of lagged consequences of
adolescent risk manifesting in internal consequences in mid-life is intriguing and
matches the data well, it only speaks to the mid-life spike in the M:F MR function
associated with internal causes. Kruger and Nesse’s (2006) data demonstrates
that a spike in the M:F MR resulting from external causes is also observed at this
same mid-life point. This fact warrants study.
Hypothesis: Divorce Rate as Possibly Underlying the Mid-Life Spike in the
M:F MR
According to Kruger and Nesse (2006), males in the midlife age range are
more likely to die from internal causes brought on as a result of the risky
behavior that the males had participated in while in young adulthood. However,
this explanation does not address why men (relative to women) at this age die of
external causes at a rate that exceeds the rates found in the years between 25
and 40.
CURRENT ANALYSIS
The current analysis varies from Kruger and Nesse’s (2006) original work as it
focuses specifically on why the rate for the M:F MR for external causes of death is
still relatively high. Drawing upon past research from U.S. 2001 Census data for
marriage (Kreider, 2005); psychological research concerning how marriage
influences male behavior (Mazur & Michalek, 1998) and how risk-taking behavior is
related to mate choice and marriage (Kruger & Nesse, 2006); and parental
investment (Trivers, 1972), we predicted that marriage and divorce patterns would
correspond to fluctuations in the M:F MR (Kruger & Nesse 2006). Essentially, we
argue that the external causes of death spike found in males during midlife is likely
the result of courtship conflict, much as the spike in late adolescence is. This timing of
the midlife spike corresponds strongly to the timing of first and second divorces that
are encountered by a high proportion of males as they enter into midlife (Kreider,
2005). More generally, an analysis of divorce rates in males shows that divorce
shows a dramatic increase in probability in males in their 40s (Kreider, 2005;
Stevenson & Wolfe, 2007). This considerable increase in likelihood of divorce (or, per
the relevant argument, being single again) maps strongly onto this second peak in
the M:F MR documented by Kruger and Nesse (2006), which takes place primarily in
one's 40s. Further, this function tends to level off at about age 50 again, strongly
consistent with Kruger and Nesse's (2006) data regarding age-related trends and the
M:F MR. If a high proportion of adult males in midlife are single within a population at
a given time, then a high proportion of midlife males, who are still reproductively
viable, are predicted to engage in male-male competition seeking access to females;
furthermore, a great deal of research shows that males in this scenario tend to seek
Divorce and M:F MR
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2015, Volume 6(2), pp. 33-41.
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relatively younger females in this process (see Kenrick & Keefe,1992), suggesting the
attraction to more viable mates is also present at this time.
So in light of standard divorce patterns, which leads to a high prevalence of
midlife single males in the population, a significant amount of male/male competition
is expected to manifest. And while this competition may be expected to reflect
relatively mature behaviors and decisions, from an evolutionary perspective, a 45-
year-old single male and a 20-year-old single male, actually have a lot in common.
They are both members of the sex that invests minimally in parental investment
(Buss & Barnes, 1986) and are both members of the sex that benefits more from
engaging in short-term mating opportunities (Schmitt, 2005). And they are both
members of the sex that has been shaped by evolution to engage in relatively
physical competition (Buss, 2005) ultimately as such physicality relates to the
competition for mates. With this analysis, it is little wonder that midlife males who find
themselves single would engage in the same kinds of behaviors that typically
correspond to “Young Male Syndrome” (Daly & Wilson, 1985).
Patterns of divorce more generally, in fact, seem to map on well to the
functions that explicate the M:F MR. Consider, for instance, that according to the
2001 U.S. Census, the average age for men to marry is 24 years (Kreider, 2005).
And according to Kruger and Nesse (2006), the M:F MR begins to decrease around
this time as well. Thus, marriage likely has an impact on the M:F MR. Once males get
married they are less likely to participate in risky behavior. In fact, recent research
shows that risk tolerance may well be a predictor of divorce in the first place (Light &
Ahn, 2009).
Further, marriage actually has been shown to correspond to significant
hormonal changes in males. After marriage, men seem to have a decrease in
testosterone, as compared to unmarried males of the same age, a fact that may
relate to aggressive behavior (Mazur & Michalek, 1998). Along these lines, it is
noteworthy that unmarried men are more likely to participate in criminal activities and
other antisocial behavior (Mazur & Michalek, 1998). Conversely, married men may be
generally out of courtship mode, ending up largely removed from relatively intense
and potentially physical competition with other males for mates (Mazur & Michalek,
1998).
In terms of the M:F MR, after marriage, males are less likely to die from the
same kinds of external causes (accidents, homicides, suicides, etc.) that are the
primary cause of death of young men from birth to age 25 (Kruger & Nesse 2006).
So being mated and concomitant testosterone levels may well explain why the M:F
MR for external causes is relatively low between the ages of 25-40, and why it shows
a clear spike during the infamous midlife stage.
Divorce Patterns and Specific External Causes of Death
Kruger and Nesse (2006) break the M:F MR for external causes into different
categories of automobile accidents, other kinds of accidents, suicides, and
homicides. Of these causes, accidents (both auto and non-auto) both show a slight
increase in midlife and homicide shows a larger increase (see, Kruger & Nesse
2006).
Divorced, single males experiencing a “midlife crisis” may be more likely to take
risks in various ways this pattern would result in increased deaths from accidents
(vehicular and otherwise). The stereotype of a man in midlife crisis depicts him with
a fast car or motorcycle (the ultimate vehicle of youth and rebellion) and a young
Divorce and M:F MR
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2015, Volume 6(2), pp. 33-41.
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woman. Although this is a stereotype, it may well be empirically accurate as well.
However, further research is needed to examine this issue.
DISCUSSION
The Male-to-Female Mortality Ratio provides a major marker of sex
differences in mortality across the lifespan and evolutionary approaches to
understanding sex differences in mortality by examining this ratio have been quite
illuminating (Kruger & Nesse, 2006; Kruger & Nesse, 2007). Prior research on this
topic has not explicitly addressed the potential role of divorce patterns on this ratio.
Specifically, we examined divorce patterns as possibly playing a role in the increase
in M:F MR that emerges during the midlife years.
Kruger and Nesse (2006) argue that this increase is largely a delayed result
of risky male behavior that is expressed in late adolescence and early adulthood in
a courtship context. They specifically argue that early death in midlife may be the
result of such risky behaviors as alcohol and drug consumption from earlier in life.
While this explanation addressed the spike in the M:F MR for internal causes found
in the data, it does not address the additional spike in external causes that also
emerges in midlife in the same data set.
By examining data speaking to divorce trends, we were able to show that
male divorce patterns seem to correspond strongly to the midlife M:F MR spike in
external causes documented by Kruger and Nesse (2006). We suggest that males
at midlife who find themselves single are, from an evolutionary perspective, in a
very similar situation to young adult males who are engaged in the mate-selection
process. Thus, the same explanation that Kruger and Nesse (2006) employ to
explain the increase in the M:F MR in the late teens / early 20s may apply to the
spike in the M:F MR in midlife. Recently single midlife men may be in their 40s and
50s chronologically, but from an ecological and evolutionary standpoint, they still
suffer from Young Male Syndrome (Daly & Wilson, 1985). In effect, this analysis
paints a portrait of the midlife crisis from an evolutionary perspective.
Testable Hypotheses for Future Research
While the current analysis provides support for the midlife increase in M:F
MR regarding external causes of death, the work here does not provide data to
directly address several proximate issues that may underlie this explanation. As a
guide for future researchers on this topic, we propose the following testable
hypotheses that are predicted by the model provided in this work.
Hypothesis 1: Recently divorced males manifest higher levels of
testosterone compared with married men from the same demographic group.
Hypothesis 2: Recently divorced males make relatively risky decisions
compared with married men from the same demographic group.
Hypothesis 3: Recently divorced males are particularly affected by status-
related primes (e.g., expensive cars, younger women) relative to comparable
increases in married men from the same demographic group.
Hypothesis 4: Recently divorced males are particularly affected by signals of
being dominated in social contexts relative to comparable increases in married men
from the same demographic group.
Divorce and M:F MR
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2015, Volume 6(2), pp. 33-41.
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Hypothesis 5: All these predicted effects regarding recently divorced males
are predicted to be exacerbated in the presence of attractive females (e.g. females
with symmetrical faces, small waist-to-hip ratio, etc.) relative to comparable
increases in married men from the same demographic group.
We hope that future research concerning the impact of marriage and
divorce can benefit from this heuristic framework.
CONCLUSION
In sum, males at middle age are a unique and understudied population.
Evolutionary psychology provides an interesting and intellectually fruitful framework
for understanding middle-aged male psychology and behavior. The current
analyses suggest that a return to courtship-like behaviors during middle age may
well account for patterns of the M:F MR during this lifestage. Clearly, this work,
then, has important health and societal implications.
Further evolutionarily informed research regarding middle-aged men may
help provide insight as to the mechanisms that are linked to their behavior. Further,
importantly, such future work may well have potential to impact behavior in a
positive manner (e.g., reducing risky behaviors), thereby having positive health
impacts at a societal level.
R
EFE
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NC
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**Received November 12, 2012; Revision received June 24, 2014; Accepted February 11,
2015
**
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The mating mind' revives and extends Darwin's suggestion that sexual selection through mate choice was important in human mental evolution - especially the more 'self-expressive' aspects of human behavior, such as art, morality, language, and creativity. Their 'survival value' has proven elusive, but their adaptive design features suggest they evolved through mutual mate choice, in both sexes, to advertise intelligence, creativity, moral character, and heritable fitness. The supporting evidence includes human mate preferences, courtship behavior, behavior genetics, psychometrics, and life history patterns. The theory makes many testable predictions, and sheds new light on human cognition, motivation, communication, sexuality, and culture.
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The evolution of a communication system depends on the existence of individuals which gain from it, that is the senders of the signals and their receivers. These two share a common interest about which they communicate. Common interests of this kind form the basis of the communication between such individuals as a sexual pair, parents and their offspring, and members of a flock or group which feed, roost or breed together. It is less often realised that individuals which are usually regarded as conflicting in their interests — for example, prey and predator, sexual rivals, a parasite and its host — may also share a common interest which may form the basis for the evolution of a communication system between them. Warning coloration, warning calls and other signals which are given by a prey species towards a predator (Smythe, 1970; Alcock, 1975) and also threat display among rivals, are some examples of signals exchanged between individuals which mainly conflict in their interest.
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