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Costs and benefits of fat-free muscle mass in men: Relationship to mating success, dietary requirements, and native immunity
Abstract
On average, men have 61% more muscle mass than women (d=3), a sex difference which is developmentally related to their much higher levels of testosterone. Potential benefits of greater male muscle mass include increased mating opportunities, while potential costs include increased dietary requirements and decreased immune function. Using data on males aged 18–59 years from the third National Health and Nutrition Examination Survey and including other relevant variables, fat-free mass (FFM) and/or limb muscle volume (LMV) are significant predictors of the numbers of total and past-year self-reported sex partners, as well as age at first intercourse. On the cost side, FFM and LMV are strong positive predictors of daily energy intake and strong negative predictors of C-reactive protein and white blood cell count, measures of native immunity.
... Male muscularity has also been studied as a potential cue to mate quality in humans. While men are approximately 10% taller than women on average (Gaulin & Boster, 1985), they are 33% heavier, have 61% more total lean muscle mass, 75% more arm muscle mass, and 90% higher upper-body strength, on average (Lassek & Gaulin, 2009). The di erence in upper-body strength is large enough that the median man has greater upper-body strength than 99.9% of women (Lassek & Gaulin, 2009). ...
... While men are approximately 10% taller than women on average (Gaulin & Boster, 1985), they are 33% heavier, have 61% more total lean muscle mass, 75% more arm muscle mass, and 90% higher upper-body strength, on average (Lassek & Gaulin, 2009). The di erence in upper-body strength is large enough that the median man has greater upper-body strength than 99.9% of women (Lassek & Gaulin, 2009). When such large sexual dimorphism of a trait is observed, it typically means that there has been sexual selection driving the exaggeration of the trait (in contrast, viability selection, which is concerned with survival, tends to act more equally on the two sexes than sexual selection, since a trait useful for survival in one sex is typically also useful for survival in the other). ...
... Similarly, using empirically derived transformations of body photographs along fat mass and muscularity dimensions, Brierley et al. (2016) found that levels of fat and muscularity that were in line with health guidelines were perceived as most attractive and healthy in men's bodies. Others have found, using regression models of ratings of photographs, that perceived physical strength strongly predicts men's attractiveness: the stronger the men appear, the more attractive they are rated (Lassek & Gaulin, 2009;Sell et al., 2017). ...
The dominant evolutionary theory of sexual attraction posits that attraction serves as a psychobehavioral and motivational mechanism for identifying healthy, fertile, and appropriate mates. According to this theory, humans and animals display cues that reflect their mate quality and, if successful, are perceived as attractive by potential mates. There is evidence for such valid cues in human faces, bodies, and non-bodily traits, which include adornments and items that signal provisioning ability, creativity, artistic skills, or conspicuous consumption. In this chapter, we discuss the evidence for the existence of these facial, bodily, and non-bodily cues and for their role in communicating aspects of partner quality, including health, fertility, developmental stability, genetic quality, and potential for parental investment. We further discuss sex differences in the physical cues that men and women rely on in mate choice. We conclude by highlighting the centrality and evolutionary importance of physical cues in contemporary sexual selection, and how they manifest in evolutionarily novel inventions such as physical self-enhancements, “sexy selfies,” social media, and online dating.
... Males are also more massive and muscular than females in all living hominid species (Plavcan, 2012). A seemingly paradoxical characteristic of sexual size dimorphism in modern humans is that skeletal dimorphism is consistent with a primate species in which males have approximately 40-50 percent more body mass (Gordon et al., 2008), and yet overall mass is greater in males by only approximately 19 percent across forager societies (Marlowe & Berbesque, 2012) and 15 percent across a broader range of societies (Kyle et al., 2001;Lassek & Gaulin, 2009;Sherry & Marlowe, 2007;Wells, 2012;table 13.4). This comparatively minor sex di erence in mass could suggest that male contest competition was weak over human evolution, and that humans are closer to monogamous species than to more polygynous ones in this regard (e.g., Fuentes, 2021; Schacht & Kramer, 2019). ...
... This comparatively minor sex di erence in mass could suggest that male contest competition was weak over human evolution, and that humans are closer to monogamous species than to more polygynous ones in this regard (e.g., Fuentes, 2021; Schacht & Kramer, 2019). However, human females have uniquely large fat stores among primates (table 13.4; g. 13.4a), and it is necessary to account for sex di erences in body composition because divergent selection pressures operate on fat and muscle, and fat stores are unlikely to aid in ghting to the same degree as lean mass and muscle mass in particular (Lassek & Gaulin, 2009). ...
... Human males additionally possess 61 percent more muscle mass overall and 75 percent more upper-body muscle mass than females (Abe et al., 2003;Lassek & Gaulin, 2009). As a result, among young adults, the average male has greater upper-body strength than 99.9 percent of females (Lassek & Gaulin, 2009). ...
Accumulating evidence suggests that the phenotypes of human males were shaped by contest competition, the mode of sexual selection in which mating opportunities are obtained by using force or threat of force to exclude same-sex competitors. Phylogenetic, paleontological, and archaeological data indicate a great antiquity for male–male violence in our lineage, and human males possess a constellation of traits that suggest specialization for contest competition. Relative to females, males exhibit greater stature, muscle mass, strength, speed, aerobic capacity, ability to dissipate exercise heat loads, craniofacial robusticity, pain tolerance, risk-taking, behavioral displays of physical prowess and acuity to the formidability of same-sex conspecifics, outgroup discrimination, and a propensity to participate in dyadic and coalitional violence. Parallel evidence suggests that some characteristics that distinguish hominins from the other great apes increase formidability in fights (e.g., handheld weapons, habitual bipedalism, and proportions of the hand and face) or function to increase perceptions of dominance (e.g., low vocal frequencies). Many of these traits are consistent with having been shaped by contest competition over mates: they develop or elaborate at sexual maturity and predict success in male contests, mating, and reproduction. Although alternative evolutionary explanations for some of these sexually dimorphic traits are possible, the most parsimonious explanation is that they have been preserved by selection because they aided in contest competition among males throughout human evolutionary history. The evolutionary roots of much of the aggression, intolerance, and violence that plagues modern societies may ultimately lie in the selection that shaped our mating system.
... For example, male muscularity is a sexually selected trait that facilitates mating competition (Puts, 2010), but it has a strong impact on women's perceptions of men's physical attractiveness (Sell et al., 2017) and positively correlates with men's short-term mating success (Lassek and Gaulin, 2009). Relatedly, Brown et al. (2022) found that men who are more physically formidable are generally perceived to be more likely to use aggressive humor. ...
... At the same time, this research adds to the body of work that clarifies the evolved function of sexually selected traits. This includes whether contests or mate choice has selected for physical aggression (Chen and Chang, 2015), male voice pitch (Puts and Aung, 2019), facial masculinity (Puts, 2010), and male muscularity (Lassek and Gaulin, 2009). It appears that those traits, now including the use of aggressive humor, are primarily selected by contests as weaponry traits. ...
Introduction:
The use of aggressive humor (e.g., teasing, schadenfreude, and sarcasm) is a spiteful behavior because it inflicts costs on both others and the self. To explain the existence of this spiteful behavior, two hypotheses derived from sexual selection theory-namely Mate-Choice and Contests-posit that the use of aggressive humor helps one attract mates or repel competitors. Both hypotheses have merit, but extant data are unable to discriminate between them.
Methods:
We critically tested those two hypotheses with a survey study that measured 509 U.S. MTurkers' self-reported tendencies to use aggressive (and other types of) humor, the motives to engage in competition and courtship, and the Dark-Triad personality traits. The final sample was N = 439.
Results:
We found that (1) the motive of competition but not courtship positively and significantly correlated with the self-reported tendency to use aggressive humor. (2) Subclinical psychopathy-a personality trait positively associated with competition-mediated the correlation between the motive of competition and self-reported use of aggressive humor. These results were held in both female and male respondents.
Discussion:
Our findings favored the Contests Hypothesis and helped reveal the psychological mechanism that generates the use of aggressive humor as a form of verbal aggression and spiteful behavior.
... As in the hips, sex differences in the breadth of the shoulder are produced by both soft tissues and the skeleton. Generally, males have significantly greater skeletal muscle mass than females, particularly in the upper limbs (Janssen et al. 2000;Lassek & Gaulin 2009). This difference in upper limb musculature in humans is not dependent on body size (Wells 2007), indicating that additional forces (natural or sexual selection; Hughes & Gallup Jr 2003) have acted on males to disproportionately increase musculature relative to females. ...
... This difference in upper limb musculature in humans is not dependent on body size (Wells 2007), indicating that additional forces (natural or sexual selection; Hughes & Gallup Jr 2003) have acted on males to disproportionately increase musculature relative to females. The three non-mutually exclusive explanations for males' greater muscle mass and upper body strength are that these traits may influence: 1) hunting and reproductive success in some human populations (Smith 2004;Gurven & Hill 2009;Apicella 2014;Lombardo & Deaner 2018), 2) success in defending or acquiring resources (Lassek & Gaulin 2009;Roach et al. 2013;Lombardo & Deaner 2018), 3) and physical intrasexual competition for mates (Morris et al. 2020). This male-biased dimorphism in upper limb musculature has also been reported in a small sample of gorillas (Zihlman & McFarland 2000), which use their upper limbs and trunk in threat displays (Wright et al. 2021) and intrasexual fights for access to females (Watts 1995). ...
Discussions of the evolution of sexual dimorphism in torso shape and the pectoral region assume that this dimorphism exists independently of body size. We test this assumption in two human populations and further examine what is needed to understand sexual dimorphism in the pectoral region. Modern human males have broad shoulders and narrow hips relative to females, lending males a more triangular torso. The wider female pelvis is commonly attributed to obstetric pressures while the broader male pectoral girdle has been argued to be an adaptation that improves hunting or intrasexual competition. While sexual dimorphism in the pelvic girdle is known to exist after adjusting for body size across human populations, most studies of sexual dimorphism in the pectoral girdle have not adjusted the data to account for sexual size dimorphism or compared different ancestral groups. The aforementioned hypotheses explaining sexual dimorphism in the clavicle and scapula as products of natural selection are predicated on the untested assumption that sex differences do not scale with body size. This study tests this assumption by comparing various measurements of the pectoral girdle, the pelvic girdle, and six pectoral-pelvic indices of black and white South Africans of known sex and height to test whether the sexes and ancestral groups will differ in these values after adjusting for differences in body size. Comparisons of ancestral groups reveal that white South Africans have larger pectoral and pelvic dimensions than black South Africans, but that blacks have larger index values than whites. Regardless of differences in ancestry and body size, males have significantly broader pectoral regions as indicated by comparisons of both individual pectoral measurements and pectoral-pelvic indices. This pattern of sexual dimorphism is reversed in the pelvic region where females have larger skeletal elements. In addition to finding both absolute and relative differences in mean values for the pectoral and pelvic skeleton, females and males and blacks and whites differ in the scaling relationship of these traits, suggesting different allometric trajectories for these bones that may be explained by their distinct evolutionary functions, their adaptations to specific environments, or by changes in lengths due to age. These results suggest that sexual dimorphism in the pectoral region is not a product of scaling and that differences in this region reflect adaptive forces acting in unique ways on each sex, consistent with the assumptions of earlier evolutionary explanations.
... On the other hand, the result was inconsistent with research done in British (4.47%), Belgium (4.2%), and Spain (10%) [18]. Also in this study, the magnitude of unplanned extubation was higher than a study reported by most studies [19]. The possible reason for this Addis Ababa governmental hospitals are the area of trainee and was loaded with junior resident which has a significant contribution to the incidence of unplanned extubation evidenced by our data. ...
... Male patients are three times more likely to experience unplanned extubation than females ( Table 4). The reason for this could be male patients are stronger than females due to the overall increase of muscle mass in the male by the effect of testosterone [19]. This could result in removing the ETT by themselves. ...
Background
Unplanned extubation is the removal of an endotracheal tube accidently during procedural activities or by the action of the patient. It is one of the commonly reported complications among mechanically ventilated patients in the intensive care unit. This study aimed to assess the magnitude and associated factors of unplanned extubation in intensive care units at referral hospitals in Addis Ababa, Ethiopia, 2021.
Methods
Institutional based prospective observational study was conducted on 317 intubated patients in the intensive care unit at referral hospitals of Addis Ababa, Ethiopia, from January 8, 2021–May 9, 2021. Data were collected using a structured questionnaire. Descriptive statics were expressed in percentages and presented with tables and figures. Both Bivariable and multivariable logistic analysis was done to identify factors associated with unplanned extubation in intensive care unit. P < 0.05 with 95% CI was set as Statistical significance.
Result
The prevalence of unplanned extubation in this study was 19.74%. Being male (AOR = 3.132, 95%CI: 1.276–7.69), duration of intubation <5days (AOR = 2.475, 95% CI: 1.039–5.894), managed by junior resident (AOR = 5.25, 95% CI: 2.125–12.969), being physically restrained (AOR = 4.356, 95%CI: 1.786–10.624), night shift (AOR = 3.282, 95%CI:1.451–7.424)and agitation (AOR = 4.934,95%CI:1.934–12.586) were significantly contribute to the occurrence of unplanned extubation.
Conclusion
and recommendation: This study showed that the prevalence of unplanned extubation was high in the intensive care unit. We suggest to intensive care unit staff to give special attention to early intubated patients, especially male individuals and the stakeholders of hospitals should rearrange the time of shift and physician schedules in the intensive care unit.
... Male facial, as well as body masculinity has been frequently viewed as cues to good health and "good genes" (i.e., genes promoting health) [39], as producing and metabolizing testosterone is costly (and might lead to higher oxidative stress) [40]. Some studies, indeed, demonstrate that high testosterone levels increase muscularity and body weight [41], as well as positively associated with facial masculinity [42,43]. Studies conducted on Caucasian samples revealed certain relationships between facial and body traits. ...
... Although, according to BMI both men and women Maasai were quite skinny, but women generally had more fat, as judged from triceps skinfolds. Other studies suggest that African men generally have higher percentage of fat-free mass (mainly muscle mass) than women, indicating that under-and-normal weight men likely had a substantial amount of muscle [41,146], and Maasai men may well fit these assumptions. Earlier, we have shown the association between physical strength (as measured by HGS) and facial shape for the same Maasai sample [121]. ...
Background
In this paper, we investigate facial sexual dimorphism and its’ association with body dimorphism in Maasai, the traditional seminomadic population of Tanzania. We discuss findings on other human populations and possible factors affecting the developmental processes in Maasai.
Methods
Full-face anthropological photographs were obtained from 305 Maasai (185 men, 120 women) aged 17–90 years. Facial shape was assessed combining geometric morphometrics and classical facial indices. Body parameters were measured directly using precise anthropological instruments.
Results
Sexual dimorphism in Maasai faces was low, sex explained 1.8% of the total shape variance. However, male faces were relatively narrower and vertically prolonged, with slightly wider noses, narrower-set and lower eyebrows, wider mouths, and higher forehead hairline. The most sexually dimorphic regions of the face were the lower jaw and the nose. Facial width-to-height ratio (fWHR), measured in six known variants, revealed no significant sexual dimorphism. The allometric effects on facial traits were mostly related to the face growth, rather than the growth of the whole body (body height). Significant body dimorphism was demonstrated, men being significantly higher, with larger wrist diameter and hand grip strength, and women having higher BMI, hips circumferences, upper arm circumferences, triceps skinfolds. Facial and body sexual dimorphisms were not associated.
Conclusions
Facial sex differences in Maasai are very low, while on the contrary, the body sexual dimorphism is high. There were practically no associations between facial and body measures. These findings are interpreted in the light of trade-offs between environmental, cultural, and sexual selection pressures.
... Gender biases in leadership access or preferences may emerge as a by-product of selection on other functions. Sexual selection has likely contributed to men's larger body size and strength (Lassek and Gaulin, 2009), and may continue to do so (Stearns et al., 2012). Upper body strength in particular is quite dimorphic in humans (Lassek and Gaulin, 2009). ...
... Sexual selection has likely contributed to men's larger body size and strength (Lassek and Gaulin, 2009), and may continue to do so (Stearns et al., 2012). Upper body strength in particular is quite dimorphic in humans (Lassek and Gaulin, 2009). Sexual selection may also have contributed to a greater tendency among men for physical or other risk-taking behaviors when pursuing leadership roles (Wilson and Daly, 1985;Mishra et al., 2017) and a greater preference among men for direct aggression in dyadic or collective competition (Archer, 1988;Van Vugt et al., 2007). ...
Social influence is distributed unequally between males and females in many mammalian societies. In human societies, gender inequality is particularly evident in access to leadership positions. Understanding why women historically and cross-culturally have tended to be under-represented as leaders within human groups and organizations represents a paradox because we lack evidence that women leaders consistently perform worse than men. We also know that women exercise overt influence in collective group-decisions within small-scale human societies, and that female leadership is pervasive in particular contexts across non-human mammalian societies. Here, we offer a transdisciplinary perspective on this female leadership paradox. Synthesis of social science and biological literatures suggests that females and males, on average, differ in why and how they compete for access to political leadership in mixed-gender groups. These differences are influenced by sexual selection and are moderated by socioecological variation across development and, particularly in human societies, by culturally transmitted norms and institutions. The interplay of these forces contributes to the emergence of female leaders within and across species. Furthermore, females may regularly exercise influence on group decisions in less conspicuous ways and different domains than males, and these underappreciated forms of leadership require more study. We offer a comprehensive framework for studying inequality between females and males in access to leadership positions, and we discuss the implications of this approach for understanding the female leadership paradox and for redressing gender inequality in leadership in humans.
... For that, PA increases later reproductive success in boys (Kirchengast & Marosi, 2009). The greater upper body muscularity and strength of males compared to females (Abe et al., 2003;Apicella, 2014;Lassek & Gaulin, 2009) propose a long history of male-male physical competition (Puts, 2010). Furthermore, low levels of adipose tissues hardly affect to males' reproduction (Bribiescas, 2001) and besides, they do not bear the cost of reproduction. ...
... Furthermore, low levels of adipose tissues hardly affect to males' reproduction (Bribiescas, 2001) and besides, they do not bear the cost of reproduction. However, under energy-constrained contexts, high levels of PA and low levels of fat tissues compromise the maintenance of the immune system (Caldwell, 2016;Lassek & Gaulin, 2009;Muehlenbein, 2010;Urlacher & Kramer, 2018). In addition, low levels of fat tissue could affect future pubertal growth (Caldwell, 2016;Urlacher & Kramer, 2018). ...
Objectives
Physical activity (PA) is required for healthy growth, development, and maturation and plays an important role in the prevention of overweight and obesity in childhood and adolescence. Sex-differences in PA levels are well documented, with boys spending more time in PA, especially in moderate-to-vigorous activities. Following the Life History Theory, our aim is to study if PA affects the fat tissues increases during childhood and juvenile phases in both sexes.
Methods
Time spent in sedentary, light, and moderate-to-vigorous PA levels were measured in a sample of 415 Portuguese children and juveniles (207 females/208 males; aged 6–11 years), using an accelerometer for 7 days. Skinfolds related with body fat were objectively collected and socioeconomic status factors were reported using a parental questionnaire.
Results
The outcomes show that girls' and boys' fat variables increased during the end of the childhood and the juvenile phase. However, these variables were differently affected by PA. Girls increased fat variables with the sedentary activity while boys decreased fat variables with moderate-to-vigorous PA. Alike, active boys but not girls reduced the fat increase tendency with age.
Conclusions
Although both sexes displayed a general fat increment with age, moderate-to-vigorous PA dampens the increase only in boys. In fact, active girls increased body fat in the same manner as non-active girls. From an evolutionary perspective, it could explain sex-specific somatic strategies related to future reproduction or, with future mating and intrasexual competition.
... With regards the albeit rather limited presence of GMV, we can test the hypothesis that it is exhibited in male sexually selected traits (due to high genetic variance), by investigating whether the traits considered most obviously to contribute to male reproductive success in the available dataset tend to be those (relatively few) that exhibit GMV. Lean muscle mass is a particularly interesting trait to consider in this regard, as greater muscle mass is purported to promote mating opportunities [46]. The traits associated with muscle (total lean mass, leg lean mass, and serum creatinine which positively associates with muscle mass) do not indicate GMV. ...
Many researchers presume greater variability between female participants than between males due to the menstrual cycle. This view has encouraged a sex bias in health and medical research, resulting in considerable knowledge gaps with important clinical implications. Yet in another field-evolutionary biology-the received wisdom is the reverse: that men are more variable, possibly due to male heterogamety. To test these competing hypotheses, we compared variance between the sexes for 50 morphological and physiological traits, analysing data from the NHANES database. Nearly half the traits did not exhibit sexual dimorphism in variation, while 18 exhibited greater female variation (GFV), indicating GFV does not dominate human characteristics. Only eight traits exhibited greater male variation (GMV), indicating GMV also does not dominate, and in turn offering scant support for the heterogamety hypothesis. When our analysis was filtered to include only women with regular menstrual cycles (and men of equivalent age), the number of traits with GFV and GMV were low and not statistically different, suggesting that the menstrual cycle does not typically explain GFV when it occurs. In practical terms, health and medical researchers should no longer simply assume that female participants will induce additional variation in the traits of interest.
... Strength is often closely connected to men's bodily attractiveness (Lidborg, Cross, & Boothroyd, 2022;Sell, Lukazsweski, and Townsley, 2017), as is muscularity (Frederick and Haselton, 2007). Fat-free muscle mass has been linked to having more sex partners (Lassek and Gaulin, 2009). However, when all types of activities aimed at increasing one's beauty were considered here, it was still women who spent more time daily enhancing their appearance compared to men, which confirms the first hypothesis. ...
People across the world and throughout history have gone to great lengths to enhance their physical appearance. Evolutionary psychologists and ethologists have largely attempted to explain this phenomenon via mating preferences and strategies. Here, we test one of the most popular evolutionary hypotheses for beauty-enhancing behaviors, drawn from mating market and parasite stress perspectives, in a large cross-cultural sample. We also test hypotheses drawn from other influential and non-mutually exclusive theoretical frameworks, from biosocial role theory to a cultural media perspective. Survey data from 93,158 human participants across 93 countries provide evidence that behaviors such as applying makeup or using other cosmetics, hair grooming, clothing style, caring for body hygiene, and exercising or following a specific diet for the specific purpose of improving ones physical attractiveness, are universal. Indeed, 99% of participants reported spending >10 min a day performing beauty-enhancing behaviors. The results largely support evolutionary hypotheses: more time was spent enhancing beauty by women (almost 4 h a day, on average) than by men (3.6 h a day), by the youngest participants (and contrary to predictions, also the oldest), by those with a relatively more severe history of infectious diseases, and by participants currently dating compared to those in established relationships. The strongest predictor of attractiveness-enhancing behaviors was social media usage. Other predictors, in order of effect size, included adhering to traditional gender roles, residing in countries with less gender equality, considering oneself as highly attractive or, conversely, highly unattractive, TV watching time, higher socioeconomic status, right-wing political beliefs, a lower level of education, and personal individualistic attitudes. This study provides novel insight into universal beauty-enhancing behaviors by unifying evolutionary theory with several other complementary perspectives.
... Given the relative dearth of evidence linking interindividual aggression rates and testosterone in male primates, behavioural and physiological traits other than aggression plausibly link dominance rank to testosterone. For instance, elevated muscle mass is an especially important somatic investment for adult male primates, a prioritization of mating effort (Bribiescas, 2001) that largely determines success in physical competition (Lassek & Gaulin, 2009;Mitani et al., 1996). Notably, body size and mass have been found to predict male dominance rank in some primates (bearded capuchins, Sapajus libidinosus: Fragaszy et al., 2016;mountain gorillas, Gorilla beringei beringei: Wright et al., 2019;rhesus macaques, Macaca mulatta: Bercovitch & Nürnberg, 1996; southern pig-tailed macaque, Macaca nemestrina: Tokuda & Jensen, 1969) and in many other vertebrates (brown trout, Salmo trutta: Jacob et al., 2007; yellow-bellied marmots, Marmota flaviventris: Huang et al., 2011;Asian elephants, Elephas maximus: Chelliah & Sukumar, 2013). ...
Testosterone promotes mating effort, which involves intraspecific aggression for males of many species. Therefore, males with higher testosterone levels are often thought to be more aggressive. For mammals living in multimale groups, aggression is hypothesized to link male social status (i.e. dominance rank) and testosterone levels, given that high status predicts mating success and is acquired partly through
aggressive intragroup competition. In male chimpanzees, Pan troglodytes, dominance rank has been repeatedly linked to interindividual variation in testosterone levels, but evidence directly linking interindividual variation in testosterone and aggression is lacking. In the present study, we test both aggression levels and lean muscle mass, as measured by urinary creatinine, as links between dominance rank and testosterone levels in a large sample of wild male chimpanzees. Multivariate analyses indicated that dominance rank was positively associated with total rates of intragroup aggression, average urinary
testosterone levels and average urinary creatinine levels. Testosterone was positively associated with creatinine levels but negatively associated with total aggression rates. Furthermore, mediation analyses showed that testosterone levels facilitated an association between dominance rank and creatinine levels.
Our results indicate that (1) adult male chimpanzees with higher average testosterone levels are often higher ranking but not more aggressive than males with lower testosterone and (2) lean muscle mass links dominance rank and testosterone levels in Ngogo males. We assert that aggression rates are
insufficient to explain links between dominance rank and testosterone levels in male chimpanzees and that other social variables (e.g. male-male relationship quality) may regulate testosterone's links to aggression.
... Studies show that human males are 15 -20% heavier and 7-8% taller than females (Isen et al., 2014) but are 90% stronger in upper body. This difference can be explained by the fact that men have 61% more total muscle mass and 75% more arm muscle mass (see Lassek and Gaulin, 2009). ...
Handgrip strength is a quick way to assess overall muscle strength. Low handgrip strength is an indicator of poor health. While handgrip strength is related with mortality and morbidity, for some parameters, handgrip strength is even a stronger predictor of health than chronological age alone. Handgrip strength is highly sexually dimorphic and has a high heritability. It is thought that this is an outcome of sexual selection and intrasexual competition in our evolutionary history. Some anthropological studies confirm this view, and it is claimed that there are relationships between grip strength and aggression, athletic performance and attractiveness, especially in men. The aim of this study is to review the relationship of diseases with handgrip strength in anthropological perspective and examine the idea that handgrip strength being a marker of biological fitness.
... Several physiological sex differences can be identified that likely resulted from this selection on males for fighting (and hunting) ability. For example, compared with women, men have greater upper body strength (e.g., Lassek & Gaulin, 2009), are taller (e.g., Gray & Wolfe, 1980), and have a higher muscle-to-fat ratio (Loomba-Albrecht & Styne, 2009). In addition, men have more interest in the practice of combat skills (Gibbons, Lynn, & Stiles, 1997), a higher tolerance for and interest in risky and dangerous activities (Kelly & Dunbar, 2001;Wilson et al., 2009), and 9 use more physical and homicidal violence (Daly & Wilson, 1988). ...
The interface of sexual behavior and evolutionary psychology is a rapidly growing domain, rich in psychological theories and data as well as controversies and applications. With nearly eighty chapters by leading researchers from around the world, and combining theoretical and empirical perspectives, The Cambridge Handbook of Evolutionary Perspectives on Sexual Psychology is the most comprehensive and up-to-date reference work in the field. Providing a broad yet in-depth overview of the various evolutionary principles that influence all types of sexual behaviors, the handbook takes an inclusive approach that draws on a number of disciplines and covers nonhuman and human psychology. It is an essential resource for both established researchers and students in psychology, biology, anthropology, medicine, and criminology, among other fields. Volume 2: Male Sexual Adaptations addresses theory and research focused on sexual adaptations in human males.
... In this conflict, researchers have argued for a coevolution of sexual dimorphism in formidability due to men's engagement in intrasexual competition. This would lead men to engage more frequently in physical conflict and consequently becoming physically larger than women, with the most successful men being larger themselves (Lassek & Gaulin, 2009;Sell et al., 2012). This asymmetry appears sexually selected, with selection favoring formidable men Puts, 2010). ...
Physical conflict has been historically prevalent throughout human evolution, with physically strong men possessing an advantage. To reduce the likelihood of incurring continued costs of conflict, opponents may engage in postconflict reconciliation to secure valuable social relationships. Two studies considered how formidability of male combatants informs expectations of reconciliatory behavior. In Study 1, participants reported expectations of respect exchanges between combatants, both following wins and losses, who were physically strong and weak. Study 2 tasked men with reporting their expectations for respect exchanges with strong and weak opponents following wins and losses. Strong targets were consistently expected to receive more respect following conflict. Nonetheless, male perceivers intended to display more respect against strong opponents regardless of fight outcome. Men’s upper body strength provides an important cue in shaping alliances for men, particularly when the potential costs of continued conflict are salient.
... These findings that advantages in size, strength, and power are associated with relatively subdued moral judgements may help to explain sex differences in moral judgement. Men are more likely to occupy higher occupational positions, and tend to have higher levels of embodied capital, as measured by height, weight, handgrip strength, and lean muscle tissue (Lassek & Gaulin, 2009;Mayhew & Salm, 1990;Vianna, Oliveira, Araújo, 2007). Such findings may be relevant for understanding why, e.g., a meta-analysis of 19 studies revealed a reliable difference in sensitivity to moral violations, with an effect size of d = 0.25 favouring women (You, Maeda, & Bebeau, 2011). ...
Moral judgements are often believed to be firmly grounded in rational thought. However, scholars have discovered that moral considerations are responsive to individual and contextual factors, such as contamination and disease threats. Indeed, the role of disgust and disease threats on amplifying judgements of moral wrongdoing has been widely investigated. Likewise, there may be other forms of threat that similarly fortify condemnation across multiple domains of morality. To explore this possibility, I conducted three lines of research, as reported in Chapters 2 through 4 of this thesis. I hypothesized that worry about contracting an illness in the midst of an ongoing pandemic, heightened risk perception as a consequence of senescence, and the presence or prospect of social exclusion would lead individuals to rate moral transgressions as more objectionable. In Chapter 2, I examined whether individual differences in concern about the ongoing COVID-19 pandemic were associated with stricter judgements of moral wrongdoing across the five moral foundations of harm/care, fairness/reciprocity, ingroup/loyalty, authority/respect, and purity/degradation. Results showed that from March-May of 2020, individuals who were more worried about a previously unknown type of coronavirus (SARS-CoV-2) and contracting the associated COVID-19 disease were harsher in their evaluations of unrelated moral wrongdoing, relative to individuals who were less worried. Results held when controlling for political orientation, suggesting fear of illness was driving the effect, rather than ideological beliefs. Moreover, there was suggestive evidence that moral condemnation intensified across the time periods tested, perhaps as a function of prolonged exposure to the risk of contracting a potentially deadly communicable illness. Building on these findings concerning the relationship between physical threats and moral verdicts, Chapter 3 reports results from multiple large cross-sectional panel surveys, namely nine rounds European Social Survey and seven waves of the World Values Survey, which suggest that relative to younger adults, older adults hold stricter views about the moral domains of authority, purity, and fairness. Results held after controlling for political orientation and income. In a follow-up study on the online testing platform Prolific, older adults rated moral violations to be more objectionable than younger adults. This relationship between age and moral condemnation was mediated by risk perception, such that older adults reported higher sensitivity to risk across a number of domains, which in turn was associated with stricter moral judgements. In sum, findings were consistent with the hypothesis that threats, in this case in the form of older age and senescence, are associated with stricter moral judgements. Shifting to a different form of threat, in Chapter 4 I report findings from three studies investigating how the presence of, and sensitivity to, social exclusion is tied to stricter moral judgements. In two studies, findings revealed an indirect effect: social exclusion reduced the fundamental social needs of belonging, self-esteem, sense of control, and meaningful existence, which in turn was associated with fortified moral judgements. The indirect effect was especially pronounced for harm violations, suggesting a heightened fear of immediate personal danger in response to social exclusion. Alongside these experimental findings, a correlational study revealed a striking effect size for the relationship between social anxiety and moral condemnation, with similar associations across each of five moral content domains. Taken together, results suggest that both the experience of, and sensitivity to, social threat is associated with heightened condemnation of moral infractions. Consistent results from these three lines of work suggest that physical and social threats help to explain and predict moral judgements in response to subjective considerations of safety and well-being.
... Furthermore, men are on average physically stronger than women (Lassek & Gaulin, 2009). It follows that, ceteris paribus, an abusive male partner could cause more physical harm to his female partner than the other way round. ...
Intimate relationships are not easy to keep as the high rates of divorce and singlehood testify. The current research aimed to examine the behavioral acts which are likely to have a negative effect on people's willingness to continue an intimate relationship. More specifically, by using qualitative research methods on a sample of 269 Greek-speaking participants, Study 1 identified 88 acts that have a negative impact on people's willingness to continue an intimate relationship. Study 2 employed quantitative research methods on a sample of 536 Greek speaking participants, and classified these acts into six broader factors. The one with the most negative impact was rated to be the "Does not care about me," followed by the "Does not treat well our children," and the "Tries to control me." Women and single participants rated the identified factors more negatively than men and participants who were in a relationship or married. Significant main effects of age, sex, relationship status and having children were also found for several factors.
... In this context, women prioritize traits that connote good genes and emphasize physical attractiveness in their mate preferences (Conroy-Beam & Buss, 2017;Kenrick et al., 1993;Li et al., 2013;Li & Kenrick, 2006). Men's desirability in STM is rooted in bodily features diagnostic of upper body strength (Puts, 2010), as evidenced by strong men reporting greater reproductive success (Gallup et al., 2007;Lassek & Gaulin, 2009). Women prefer muscular men as short-term mates (Frederick & Haselton, 2007;Sacco, Jones, et al., 2012;Sacco, Young, et al., 2012), while also reporting similar preferences for large chests and masculinized faces (Garza & Byrd-Craven, 2021;Jones et al., 2018;Sacco, Jones, et al., 2012;Sacco, Young, et al., 2012). ...
Women find men's upper body strength highly desirable, albeit primarily within short‐term mating contexts. This boundary implicates strength as possessing both costs and benefits in long‐term and short‐term mating contexts. The desirability of strength could be contingent upon whether the costs or benefits of strength are more salient through additional behavioral repertoires that signal a specific type of mating intent. Men's humor style could be one modality to infer costs and benefits, namely their interest in affiliative humor relative to aggressive humor. This study represents a synergistic replication of previous work investigating the desirability of strength and various humor styles in mating domains. Women evaluated the short‐term and long‐term desirability of a prospective mate manipulated to appear physically strong or weak and described using affiliative or aggressive humor. We replicated previous findings implicating affiliative humor as desirable in long‐term contexts and upper body strength in short‐term contexts. However, no interactive effects between these traits emerged. Results indicate that women's mate choices are multimodal and frequently involve evaluating the costs and benefits of various constellations of traits.
... Strength is often closely connected to men's bodily attractiveness (Lidborg, Cross, & Boothroyd, 2022;Sell, Lukazsweski, and Townsley, 2017), as is muscularity (Frederick and Haselton, 2007). Fat-free muscle mass has been linked to having more sex partners (Lassek and Gaulin, 2009). However, when all types of activities aimed at increasing one's beauty were considered here, it was still women who spent more time daily enhancing their appearance compared to men, which confirms the first hypothesis. ...
People across the world and throughout history have gone to great lengths to enhance their physical appearance. Evolutionary psychologists and ethologists have largely attempted to explain this phenomenon via mating preferences and strategies. Here, we test one of the most popular evolutionary hypotheses for beauty-enhancing behaviors, drawn from mating market and parasite stress perspectives, in a large cross-cultural sample. We also test hypotheses drawn from other influential and non-mutually exclusive theoretical frameworks, from biosocial role theory to a cultural media perspective. Survey data from 93,158 human participants across 93 countries provide evidence that behaviors such as applying makeup or using other cosmetics, hair grooming, clothing style, caring for body hygiene, and exercising or following a specific diet for the specific purpose of improving ones physical attractiveness, are universal. Indeed, 99% of participants reported spending >10 min a day performing beauty-enhancing behaviors. The results largely support evolutionary hypotheses: more time was spent enhancing beauty by women (almost 4 h a day, on average) than by men (3.6 h a day), by the youngest participants (and contrary to predictions, also the oldest), by those with a relatively more severe history of infectious diseases, and by participants currently dating compared to those in established relationships. The strongest predictor of attractiveness-enhancing behaviors was social media usage. Other predictors, in order of effect size, included adhering to traditional gender roles, residing in countries with less gender equality, considering oneself as highly attractive or, conversely, highly unattractive, TV watching time, higher socioeconomic status, rightwing political beliefs, a lower level of education, and personal individualistic attitudes. This study provides novel insight into universal beauty-enhancing behaviors by unifying evolutionary theory with several other complementary perspectives.
... We hypothesized that women receiving prolonged grandmothers' instrumental support were more likely to have received advice about breastfeeding and would therefore have more favorable attitudes and practices regarding breastfeeding that, in turn, would be associated with more favorable body composition in their children (greater length and lean mass, lower body fatness). While body fat promotes short-term survival in early life (Kuzawa, 1998;Wells, 2010b), in adulthood a greater proportion of lean mass is associated with reproductive fitness in both sexes (Lassek & Gaulin, 2009;Wells, 2018). Therefore, the mother can maximize her own reproductive success by investing in offspring lean mass (Wells, 2018). ...
Abstract
Objectives
Breast-feeding is sensitive to somatic, hormonal, behavioral and psychological components of maternal capital. However, through grandmothering, older women may also influence breast-feeding by transferring informational resources to their daughters. We hypothesized that mothers with prolonged instrumental support from their own mother are more likely to have received advice and to have favorable attitudes/practices regarding breastfeeding, compared to those lacking such support, with implications for the grandchild's somatic capital.
Methods
We recruited 90 mother-infant dyads (52 with grandmaternal support, 38 without) in Merida, Yucatan, Mexico. All children were first-borns, aged ~2 years. Anthropometry and body composition were assessed. Data on grandmother's breastfeeding advice and maternal breastfeeding duration were obtained by questionnaire. Maternal attitudes to breast-feeding were assessed using the Iowa Infant Feeding Attitude Scale.
Results
Women with instrumental support were more likely to have received grandmaternal advice during pregnancy/infancy on exclusive breast-feeding duration (60% vs. 37%, p = 0.033) and the type of first complementary food (81% vs. 47%, p = 0.001). However, women with support had a less favorable attitude to breastfeeding than those without and breastfed their children for less time (median 5 vs. 10.5 months, p = 0.01). No group differences were found in children's length, weight, skinfolds or lean mass z-score.
Discussion
Although grandmothers providing instrumental support provided advice regarding breastfeeding, their attitudes may reflect issues beyond nutritional health. Advice of maternal grandmothers did not promote extended breastfeeding, however the differences in breastfeeding attitudes were not associated with the children's nutritional status. Grandmothers should be included in public health interventions promoting breastfeeding.
... Strength is often closely connected to men's bodily attractiveness (Lidborg, Cross, & Boothroyd, 2022;Sell, Lukazsweski, and Townsley, 2017), as is muscularity (Frederick and Haselton, 2007). Fat-free muscle mass has been linked to having more sex partners (Lassek and Gaulin, 2009). However, when all types of activities aimed at increasing one's beauty were considered here, it was still women who spent more time daily enhancing their appearance compared to men, which confirms the first hypothesis. ...
People across the world and throughout history have gone to great lengths to enhance their physical appearance. Evolutionary psychologists and ethologists have largely attempted to explain this phenomenon via mating preferences and strategies. Here, we test one of the most popular evolutionary hypotheses for beauty-enhancing behaviors, drawn from mating market and parasite stress perspectives, in a large cross-cultural sample. We also test hypotheses drawn from other influential and non-mutually exclusive theoretical frameworks, from biosocial role theory to a cultural media perspective. Survey data from 93,158 human participants across 93 countries provide evidence that behaviors such as applying makeup or using other cosmetics, hair grooming, clothing style, caring for body hygiene, and exercising or following a specific diet for the specific purpose of improving ones physical attractiveness, are universal. Indeed, 99% of participants reported spending >10 min a day performing beauty-enhancing behaviors. The results largely support evolutionary hypotheses: more time was spent enhancing beauty by women (almost 4 h a day, on average) than by men (3.6 h a day), by the youngest participants (and contrary to predictions, also the oldest), by those with a relatively more severe history of infectious diseases, and by participants currently dating compared to those in established relationships. The strongest predictor of attractiveness-enhancing behaviors was social media usage. Other predictors, in order of effect size, included adhering to traditional gender roles, residing in countries with less gender equality, considering oneself as highly attractive or, conversely, highly unattractive, TV watching time, higher socioeconomic status, right-wing political beliefs, a lower level of education, and personal individualistic attitudes. This study provides novel insight into universal beauty-enhancing behaviors by unifying evolutionary theory with several other complimentary perspectives.
... Decades of research have assessed physical differences and performance differences between biological men (XY) and women (XX). For example, on average, men tend to be taller than women (NCD Risk Factor Collaboration, 2016), weigh more than women (Loomba-Albrect & Styne, 2009), have greater upper body strength (Lassek & Gaulin, 2009), display more accuracy when throwing (Jardine & Martin, 1983), and testosterone is 10-15 times higher in men than women following puberty (Handelsman & Sikaris, 2016). In fact, "even when [female] testosterone is pathologically raised in polycystic ovarian syndrome the values are still a fraction (˜1/20th) of that observed in males" (Nelson et al., 2020, p. 2). ...
There is more sexuality diversity in women’s sports than in men’s sports. This makes the Women’s National Basketball Association (WNBA)one of the only sports where a comparison of athletic performance based on sexuality is possible. Sex differences in athletic performance emerge during puberty, due in part to increases in circulating testosterone in men. Research has also found that lesbians and bisexual women have more testosterone than straight women. Thus, it is possible that there are differences in women’s athletic performance based on sexual orientation. In this study, we used publicly available information to determine the sexual orientation of current WNBA players and compared performance statistics based on sexuality. Results showed that lesbian guards are more accurate shooters with a significantly higher field goal percentage than straight guards, and, regardless of position, lesbian players averaged more assists per game. Aside from these findings, overall performance was similar regardless of athletes’ sexual orientation. We argue that no athlete should be discounted based on sexual orientation, whether straight athletes in women’s sports or gay athletes (like Michael Sam) in men’s sports.
https://www.arcjournals.org/pdfs/ijhsse/v9-i4/2.pdf
... But total body mass provides only a crude picture of the forces shaping these sex differences because, on average, men and women allocate that mass much differently (Plavcan, 2012b). Women have considerably more fat and men have more lean (and muscle) mass (Pond, 1998;Kyle et al., 2005;Wells, 2007Wells, , 2012aLassek and Gaulin, 2009;Hill et al., 2017;Puts et al., in press). Because these sex differences in body composition are present but significantly less pronounced in infants and children and increase dramatically with puberty (Wells, 2007;Kirchengast, 2010;Taylor et al., 2010), this is an ontogenetic sign that they are related to the different reproductive strategies of the two sexes, as explored below. ...
Human sexual dimorphism has been widely misunderstood. A large literature has underestimated the effect of differences in body composition and the role of male contest competition for mates. It is often assumed that sexually dimorphic traits reflect a history of sexual selection, but natural selection frequently builds different phenotypes in males and females. The relatively small sex difference in stature (∼7%) and its decrease during human evolution have been widely presumed to indicate decreased male contest competition for mates. However, females likely increased in stature relative to males in order to successfully deliver large-brained neonates through a bipedally-adapted pelvis. Despite the relatively small differences in stature and body mass (∼16%), there are marked sex differences in body composition. Across multiple samples from groups with different nutrition, males typically have 36% more lean body mass, 65% more muscle mass, and 72% more arm muscle than women, yielding parallel sex differences in strength. These sex differences in muscle and strength are comparable to those seen in primates where sexual selection, arising from aggressive male mating competition, has produced high levels of dimorphism. Body fat percentage shows a reverse pattern, with females having ∼1.6 times more than males and depositing that fat in different body regions than males. We argue that these sex differences in adipose arise mainly from natural selection on women to accumulate neurodevelopmental resources.
... This is true for several reasons. First, the sex difference in Emotionality is 18 Based on the foregoing, we made the following predictions, which are pre-registered at 19 https://osf.io/d3hk4?view_only=e6f9e5cd7ba54cc39de95411f252a086. 3. The sex difference in the overall HEXACO Emotionality factor is mediated by 3 physical strength. ...
Across cultures, women reliably exhibit higher levels of Neuroticism than men. Recent work shows that this sex difference, particularly in Neuroticism’s anxiety facet, is partly mediated by the sex difference in physical strength. We build on this finding by testing pre-registered predictions of mediation by physical strength of the sex differences in HEXACO Emotionality and its Anxiety and Fearfulness facets (HEXACO stands for the factors of honesty–humility, emotionality, extraversion, agreeableness, conscientiousness, and openness to experience). Facultative calibration models predict that levels of these two facets, but not necessarily Emotionality’s other facets, will be adaptively adjusted during ontogeny to a person’s relative physical formidability. Results from five samples of U.S. undergraduates (total N = 1,399) showed that strength mediated the sex difference (women > men) in Emotionality and all its facets, but that the mediation effect was strongest for Fearfulness and weakest for Sentimentality. Overall, findings are consistent with the hypothesis that physical strength explains sex differences found in fearful and anxious personality traits.
... On average, men have 61% more overall muscle mass and 78% more muscle mass in the upper arms. This concentrated muscle dimorphism in the arms and back translates to 90% greater upper body strength in men than women [33]. Using National Health and Nutrition Examination Survey (NHANES) data, we found that, in 95.7% of random encounters between a woman and man, the man would have higher grip strength. ...
Background:
Depression occurs about twice as often in women as in men, a disparity that remains poorly understood. In a previous publication, Hagen and Rosenström predicted and found that grip strength, a highly sexually dimorphic index of physical formidability, mediated much of the effect of sex on depression. Striking results like this are more likely to be published than null results, potentially biasing the scientific record. It is therefore critical to replicate and extend them.
Methodology:
Using new data from the 2013-14 cycle of the National Health and Nutrition Examination Survey, a nationally representative sample of US households (n = 3650), we replicated models of the effect of sex and grip strength on depression reported in Hagen and Rosenström, along with additional potential confounds and a new detailed symptom-level exploration.
Results:
Overall, the effects from the original paper were reproduced although with smaller effect sizes. Grip strength mediated 38% of the effect of sex on depression, compared to 63% in Hagen and Rosenström. These results were extended with findings that grip strength had a stronger association with some depression symptoms, like suicidality, low interest and low mood than with other symptoms, like appetite changes.
Conclusions:
Grip strength is negatively associated with depression, especially its cognitive-affective symptoms, controlling for numerous possible confounds. Although many factors influence depression, few of these reliably occur cross-culturally in a sex-stratified manner and so are unlikely to explain the well-established, cross-cultural sex difference in depression. The sex difference in upper body strength occurs in all populations and is therefore a candidate evolutionary explanation for some of the sex difference in depression. Lay summary: Why are women at twice the risk of developing depression as men? Depression typically occurs during social conflicts, such as physical or sexual abuse. Physically strong individuals can often single-handedly resolve conflicts in their favor, whereas physically weaker individuals often need help from others. We argue that depression is a credible cry for help. Because men generally have greater strength than women, we argue that men may be more likely to resolve conflicts using physical formidability and women to signal others for help. We find that higher grip strength is associated with lower depression, particularly symptoms like feeling down or thoughts of suicide and that strength accounts for part of the sex difference in rates of depression.
... MMC underscores the reduced effect size of sexual dimorphism, relative to magnitudes in other sexually dimorphic species, in several psychological traits. For example, even though intelligence, language, and humor have been discussed, in part, as ornaments and targets of sexual selection, these are not indubitably sexually dimorphic in comparison to physical traits such as height (Lippa, 2009), muscle mass, strength (Lassek & Gaulin, 2009), and vocal pitch (Puts et al., 2016). Additionally, given that humans are a pair bonding species with paternal investment, the MMC model especially highlights assortative mating (also proposed by Buss, 1984) where both men and women estimate and respond to cues of heritable fitness in self and potential partners. ...
The historical mating practices of a South Indian community, the Nayars, have often been cited as an example of matriliny and polyandry. Little attention has been given to puritanical aspects of their conjugal unions involving endogamy and hypergamy. We adopt an evolutionary psychology perspective to reexamine these practices. We outline key historical events to situate the Nayar case in the broader Indian context and compare different evolutionary psychology models of sexual strategies to determine the most befitting one. The unique mating arrangements provide a novel opportunity to appraise the focal points of the different models involving fitness-indicators, resource provisioning, parenting, and the temporality of the mating context. This exercise helps in revealing the primacy of assortative mating and perceived mate quality based on prestige-markers, despite the incertitude about resource provisioning or other direct benefits.
... This is a trait that covaries with strength and, therefore, it is convenient to control its effect when studying strengthrelationships with other traits (Lassek and Gaulin, 2009). The participants' weight (in kilograms) was measured using a digital body scale and their height (in centimeters) was obtained using a stadiometer (SECA 213). ...
From an evolutionary perspective, phenotypic, social, and environmental factors help to shape the different costs and benefits of pursuing different reproductive strategies (or a mixture of them) from one individual to another. Since men’s reproductive success is mainly constrained to women’s availability, their mating orientations should be partially calibrated by features that women prefer in a potential partner. For long-term relationships, women prefer traits that signal access to resources, protection skills, and the willingness to share them. Using generalized linear models with laboratory data taken from a Chilean population ( N = 197), this study aimed to test whether real and potential resources (measured as self-reported socioeconomic status), protection skills (measured as handgrip strength), and the willingness to provide resources and protection (measured as their disposition toward parenthood) are related to mating orientation in men. Our predictions were: (1) socioeconomic status would be positively associated with long-term and short-term mating orientation but for long-term-oriented individuals, this would be enhanced by having a more favorable parenthood disposition and (2) strength would be positively related to long-term mating orientation in men with higher socioeconomic status and a favorable disposition toward parenthood and it would have a positive and direct association with short-term mating orientation. Our results partially supported the first hypothesis, since men with higher socioeconomic status were more long-term oriented, but parenting disposition did not moderate this effect. Contrary to our expectations, socioeconomic status was not related to short-term mating orientation. Strength appeared not to be significant for long-term mating orientation, even interacting with other traits. However, strength by itself was powerfully linked with a short-term mating orientation. Our results suggest that only some individuals that are attractive for long-term relationships are indeed long-term oriented and may reflect the overall conflict of interests between mating strategies among sexes.
... In total, 96 studies were selected (Lassek and Gaulin, 2009;Hughes and Gallup, 2003;Weeden and Sabini, 2007;Frederick and Haselton, 2007;Lukaszewski et al., 2014;Hill et al., 2013;Kordsmeyer et al., 2018;Peters et al., 2008;Boothroyd et al., 2017;Pawlowski et al., 2008;Arnocky et al., 2018;Rhodes et al., 2005;Van Dongen and Sprengers, 2012;Alvergne et al., 2009;Apicella, 2014;Apicella et al., 2007;Aronoff, 2017;Atkinson, 2012;Atkinson et al., 2012;Bogaert and Fisher, 1995;Booth et al., 1999;Boothroyd et al., 2011;Boothroyd et al., 2008;Charles and Alexander, 2011;Chaudhary et al., 2015;Edelstein et al., 2011;Falcon, 2016;Farrelly et al., 2015;Frederick, 2010;Frederick and Jenkins, 2015;Gallup et al., 2007;Genovese, 2008;Gettler et al., 2019;Gildner, 2018;(Gómez-Valdés et al., 2013) Hartl et al., 1982;Hoppler et al., 2018;Honekopp et al., 2007;Kirchengast, 2000;Kirchengast and Winkler, 1995;Klimas et al., 2019;Klimek et al., 2014;Kordsmeyer and Penke, 2017;Krzyżanowska et al., 2015;Kurzban and Weeden, 2005;Little et al., 1989;Loehr and O'Hara, 2013;Longman et al., 2018;Luevano et al., 2018;Maestripieri et al., 2014;Manning and Fink, 2008;Manning et al., 2003;Marczak et al., 2018;McIntyre et al., 2006;Međedović and Bulut, 2019;Mosing et al., 2015;Muller and Mazur, 1997;Nagelkerke et al., 2006;Nettle, 2002;Pawlowski et al., 2000;Pollet et al., 2011;Polo et al., 2019;Price et al., 2013;Prokop and Fedor, 2011;Prokop and Fedor, 2013;Puts et al., 2006;Puts et al., 2015;Putz et al., 2004;Rahman et al., 2005;Rosenfield et al., 2020;Schwarz et al., 2011;Scott and Bajema, 1982;Shoup and Gallup, 2008;Sim and Chun, 2016;Simmons and Roney, 2011;Smith et al., 2017;Sneade and Furnham, 2016;Sorokowski et al., 2013;Steiner, 2011;Stern et al., 2020;Strong, 2014;Strong and Luevano, 2014;Subramanian et al., 2009;Suire et al., 2018;Tao and Yin, 2016;van Anders et al., 2007;Varella et al., 2014;von Rueden et al., 2011;Voracek et al., 2010;Walther et al., 2016;Walther et al., 2017c;Walther et al., 2017a;Walther et al., 2017b;Waynforth, 1998;Winkler and Kirchengast, 1994;Honekopp et al., 2006), comprising 474 effect sizes from 99 samples and 177,044 unique participants (Table 1). This exceeds the number of studies for each of the meta-analyses published previously (Grebe et al., 2019;Van Dongen and Sprengers, 2012;von Rueden and Jaeggi, 2016;Xu et al., 2018). ...
Humans are sexually dimorphic: men and women differ in body build and composition, craniofacial structure, and voice pitch, likely mediated in part by developmental testosterone. Sexual selection hypotheses posit that, ancestrally, more 'masculine' men may have acquired more mates and/or sired more viable offspring. Thus far, however, evidence for either association is unclear. Here, we meta-analyze the relationships between six masculine traits and mating/reproductive outcomes (96 studies, 474 effects, N = 177,044). Voice pitch, height, and testosterone all predicted mating; however, strength/muscularity was the strongest and only consistent predictor of both mating and reproduction. Facial masculinity and digit ratios did not significantly predict either. There was no clear evidence for any effects of masculinity on offspring viability. Our findings support arguments that strength/muscularity may be sexually selected in humans, but cast doubt regarding selection for other forms of masculinity and highlight the need to increase tests of evolutionary hypotheses outside of industrialized populations.
... Men and women show a number of morphological, physiological and psychological sex differences, ranging from small to large, that are reflected in sex differences in sports performance. On average, men are heavier, taller and have more muscle mass, especially in the upper body (Lassek & Gaulin, 2009); men have also more oxygen aerobic power and anaerobic capacity (Handelsman et al., 2018) and, tend to show more social dominance (Hines, 2020) and competitiveness (Deaner et al., 2016) compared to women, at least in some contexts. ...
The goal of the special issue on “Sports science: evolutionary perspectives and biological mechanisms” was to build a bridge to help the development of a coherent and unifying approach to the study of sport science within an evolutionary framework. By focusing specifically on the biological and psychological dynamics of sport performance and competition, we asked if sports can be used to study the evolution of human behavior, biology and psychology. Likewise, we asked whether this evolutionary approach could improve our understandings of the physical and psychological limits of human athletic performance and health.
... Despite these affordances of warmth through features, such cues may not connote men's ability to protect their offspring. High levels of body fat present physical disadvantages that could impede success in conflict (e.g., Lassek & Gaulin, 2009), and facial hair is not a veridically diagnostic fighting ability (Dixson et al., 2018). These protective capabilities could be more reliably inferred through men's upper body strength due to both formidable men's advantages in physical conflict (Puts, 2010) and the above-chance accuracy humans demonstrate toward cues to strength (Lukaszewski et al., 2016). ...
The selection of formidable male allies within coalitional settings is partially in the service of ensuring protection from physical threats for group members. Within these inferences could include specific judgments of formidable men as being effective at providing protection for their offspring, a judgment that could facilitate identification of prospective fathers who satisfy parenting goals. The current study sought to identify the specific value of men’s physical strength in shaping perceptions of their effectiveness in domains or protection and nurturance of offspring. Participants evaluated physically strong and weak in their effectiveness in these domains. Strong men were perceived as more effective in protecting their offspring than weak men, with this advantage corresponding with strong men being perceived as less effective in nurturance. We frame results from an affordance management framework considering the role of functional inferences shaping interpersonal preferences.
... Physical strength is sexually dimorphic due to the influences of androgenic hormones and fat-free body mass, suggesting that this trait has been elaborated through sexual selection (Gallup & Fink, 2018). Men are typically taller than women (Gray & Wolfe, 1980) and have more muscle mass (Bishop, Cureton, & Collins, 1987), especially in the upper body (Lassek & Gaulin, 2009). They tend to be physically stronger than women (Butovskaya et al., 2018, for the Maasai;Guenther, Buerger, Rickert, Crispin, & Schulz, 2008, for Germany), also after controlling for the influences of body height and weight (Miller, Mac-Dougall, Tarnopolsky, & Sale, 1993;Musselman & Brouwer, 2005). ...
Male physical formidability may reflect capacities to provision and protect, resource holding potential, and social status. Handgrip strength (HGS) is a robust measure of overall muscular strength and function that correlates positively with ratings of male facial attractiveness and dominance. Here, we examine strength, attractiveness, and aggressiveness assessments as a function of facial cues to HGS in a sample of male Maasai of Northern Tanzania. Adult Maasai (56 women, 40 men) rated three strength-calibrated facial morphs of Maasai men. These morphs were constructed by performing a geometric morphometric shape regression on HGS using digital images of 54 men (20–29 years). Participants judged facial morphs calibrated to greater HGS higher on strength and attractiveness, but lower on aggressiveness. The accurate assessment of male Maasai physical strength from facial cues and the corresponding attractiveness assessments of strength cues are consistent with evolutionary predictions and previous research. The situation is less clear for the association of facial strength cues with the assessment of aggression. Future research should consider the possibility of a (feature-based) perceptual overgeneralization, especially in the interpretation of facial aggressiveness judgments, in addition to population-specific influences, and distinguish them from facial cues that indicate behavioral dispositions. Collectively, the findings of the present study corroborate the suggestion that the Maasai are sensitive to facial cues of strength and use these cues in social assessments.
... The results of the worked example are supported by a series of other studies. Greater male HGS as well as HGS variability has also been shown for German samples ( [82]; sex difference directly included in the article; variability computed as described above, for the 20-29 year olds and the right hand From an evolutionary perspective, physical strength is also sexually dimorphic, with 99.9% of women showing a weaker upper body strength than the average man [88], consistent with reports of higher HGS in men than in women [82,83]. Greater physical strength probably reflects an evolutionary history of male-male competition and physical fighting [89,90]. ...
The length ratio between the second and the fourth digit (2D : 4D) is a retrospective, non-invasive biomarker for prenatal androgen exposure. It was found to be negatively correlated with handgrip strength (HGS) in men, but the evidence for women is mixed. Such studies in women call for increased detection sensitivity. The present study was designed to reduce potential confounding factors, especially age and ethnicity variation. We measured the digit ratios and HGS of 125 healthy women between 19 and 31 years of age from a remote region in Austria. 2D : 4D of both hands was significantly and negatively correlated with HGS ( n = 125, right hand: r = –0.255, p = 0.002, left hand: r = –0.206, p = 0.011). Size, direction and significance of correlation coefficients remained stable when statistically controlling for age, body weight, body height, body mass index or hours of exercise per week. This yields theory-consistent evidence that HGS and 2D : 4D are clearly associated in women—when sufficiently reducing genetic variation (confounding 2D : 4D), the ontogenetic environment and age ranges (confounding HGS) in the study population. This finding implies similar organizing effects of prenatal androgens as in men, pointing to a more parsimonious developmental mechanism and a new look into its proximate and ultimate causes.
... In line with this, in previous studies, effects of single traits and characteristics on correlates of evolutionary fitness like reproductive success (or mating success, which is moderately strongly related to reproductive success, Puts et al., 2015) were mostly non-significant or, if significant, small or not robust. Some associations with mating and/or reproductive success have been found for physical attractiveness (e.g., Jokela, 2009;Pflüger et al., 2012;Rhodes et al., 2005; but see Hill et al., 2013 andKordsmeyer et al., 2018 for null-findings), status measures (e.g., communitywide influence/prestige, political leadership, or wealth in men in a small-scale indigenous population, von Rueden & Jaeggi, 2016;von Rueden et al., 2011), physical dominance (e.g., physical strength, muscularity, and body as well as vocal masculinity in men, Frederick & Haselton, 2007;Hill et al., 2013;Kordsmeyer et al., 2018;Lassek & Gaulin, 2009), intelligence (e.g., Greengross & Miller, 2011; for an inverse association see Hopcroft, 2006), education (inversely, Hopcroft, 2006), income (in men but not women, Barthol et al., 2012;Hopcroft, 2006), height (positive linear and negative curvilinear effects in men, Nettle, 2002a;Stulp et al., 2012a; but see Hill et al., 2013 andKordsmeyer et al., 2018 for null-effects; negative linear and curvilinear associations in women, Nettle, 2002b;Stulp et al., 2012b), and baseline testosterone levels (in men, as a potential proxy measure of health based on the immunocompetence hypothesis, e.g., Folstad & Karter, 1992;Rantala et al., 2012). Some further effects appeared to be significant in a linear way in men, but not women (e.g., for height, Stulp et al., 2012b). ...
According to evolutionary theory, human cognition and behaviour are based on adaptations selected for their contribution to reproduction in the past, which in the present may result in differential reproductive success and inclusive fitness. Because this depiction is broad and human behaviour often separated from this ultimate outcome (e.g., increasing childlessness), evolutionary theory can only incompletely account for human everyday behaviour. Moreover, effects of most studied traits and characteristics on mating and reproductive success turned out not to be robust. In this article, an abstract descriptive level for evaluating human characteristics, behaviour, and outcomes is proposed, as a predictor of long-term reproductive success and fitness. Characteristics, behaviour, and outcomes are assessed in terms of attained and maintained capital, defined by more concrete (e.g., mating success, personality traits) and abstract (e.g., influence, received attention) facets, thus extending constructs like embodied capital and social capital theory, which focuses on resources embedded in social relationships. Situations are framed as opportunities to gain capital, and situational factors function as elicitors for gaining and evaluating capital. Combined capital facets should more robustly predict reproductive success and (theoretically) fitness than individual fitness predictors. Different ways of defining and testing these associations are outlined, including a method for empirically examining the psychometric utility of introducing a capital concept. Further theorising and empirical research should more precisely define capital and its facets, and test associations with (correlates of) reproductive success and fitness.
... It is worth noting, however, despite the control group being age, gender, and ethnicity matched, they were not matched for body mass index or body composition, which is a key limitation within the research, as body composition differences (ie, the muscle mass of participants) may in part explain the differences between daily energy expenditure. 43 However, much like the mechanisms behind the reduction in exercise performance, the understanding of the mechanisms behind fatigue remain unknown. Strookappe et al 26 states fatigue within sarcoidosis is multifaceted and as such, further research needs to be conducted to understand these F I G U R E 2 A schematic diagram to demonstrate the association between sarcoidosis and exercise training ...
Individuals with sarcoidosis are at risk of deconditioning and heightened non-communicable diseases through decreased muscle strength and physical activity. This systematic review analysed published data to provide an overview of the associations of physical activity and physical fitness with sarcoidosis.
A systematic search of PubMed and ScienceDirect, was conducted in April 2021 following PRISMA guidelines, to determine the association of sarcoidosis with levels of physical activity and fitness. Experimental studies of patients with sarcoidosis where cardio-respiratory capacity, physical activity and/or muscle strength were measured were selected.
Twenty-one trials with 1442 participants met the inclusion criteria. Studies (published between 1986-2018) found reduced cardio-respiratory capacity (n=17), physical activity levels (n=2) and muscle strength (n=8) within sarcoidosis patients, with those experiencing fatigue affected more than non-fatigued.
Physical activity is reduced in sarcoidosis compared to normative values, including sedentary healthy individuals. In addition, muscle strength and cardio-respiratory capacity / fitness are reduced, with individuals affected by fatigue. Three clinical exercise-intervention trials demonstrated improved muscle strength and six-minute walk distance alongside decreased fatigue ratings. The deconditioning effects of sarcoidosis, in addition to associated symptoms, can be overcome/improved by exercise. Further well-designed trials with exercise prescription are needed to establish standardised exercise recommendations specific to sarcoidosis.
... In this study, we tested whether 2D:4D digit ratio, fWHR, and musculature are related to status-seeking behavior by measuring behavioral responses in a game that contextualizes a confrontation for status. We employed the Chicken Game paradigm to evaluate the relationship between traits and responses taking into account the socioeconomic status and controlling for the Body Mass Index since affects measures of fWHR and muscle mass (Lassek & Gaulin, 2009). Accordingly, we expected that men with higher fWHR, higher SMM, and lower 2D:4D digit ratio showed a high frequency of competitive choices in the Chicken Game, especially when they reported to have a low socioeconomic status. ...
Facial width-to-height ratio (fWHR), 2D:4D digit ratio and skeletal muscle mass are morphological traits that have been linked to status-seeking behaviors throughout dominance. However, this link has been contested recently, since the empirical evidence about the relationship between these traits and behavior is mixed. In this study, we tested whether fWHR, 2D:4D digit ratio and skeletal muscle mass were related to dominant behavior employing the Chicken Game, an economic game that may represent a good scenario to investigate hierarchy formation and in which these relationships remain untested. We tested this hypothesis in a sample of 210 Chilean young men (mean = 22.43, SD = 4.35 years old) who played the Chicken Game against an anonymous same-sex individual and one-shot. Our results showed that fWHR was related to dominant choices in the Chicken Game, but null results were found for 2D:4D digit ratio and muscle mass. Accordingly, this study suggests that in a challenging but anonymous interaction only fWHR was related to dominance. Further studies using different conditions of anonymity may contribute to clarify the role of these traits in status-seeking behaviors.
... Stewart-Williams and Thomas [63] suggest that this pattern is relevant to humans as well. Human sex differences are usually modest and are stronger within one sex than between sexes and mostly concern physical traits, such as muscle mass and strength [66]. Psychological differences are much smaller [67]. ...
Creative thinking is a defining human feature. It provides novel solutions and as such undoubtedly has contributed to our survival. However, according to signaling theory, creativity could also have evolved through sexual selection as a potential fitness indicator. In our study, we tested one implication of this theory. Specifically, we hypothesized that if creativity can serve as a signal of women’s fitness, then we should observe an increase in creative thinking in the fertile phase of the ovulatory cycle compared to other non-fertile phases. In our study (N = 751), we tested creative potential throughout the ovulatory cycle. We found a positive correlation between the probability of conception and both creative originality and flexibility. Importantly, we also tested the mediating role of arousal in the relationship between the probability of conception and creative thinking. The results of our study are discussed in terms of signaling theory, through which women advertise their fitness with their creativity.
... Still, the suite of traits that endow the SH with both speed and strength can, and likely do, impose their own set of evolutionary costs. Studies show, for example, that especially large muscles can impose above-average energetic demands, and even potentially suppress native immune function (Lassek & Gaulin, 2009). Likewise, small limb muscles are associated with enhanced locomotor activity in certain contexts (Garland et al., 2002). ...
Biologists have long been fascinated by the elaborate courtship displays performed by diverse organisms throughout the animal kingdom. The evolution of courtship behaviour often requires specializations of neural, sensory and motor systems. In addition, physically impressive displays may also require optimized metabolic, respiratory and cardiovascular systems to sustain the neuromuscular demands. Hormonal signalling can reach all of these tissues simultaneously to prepare them for use in courtship. Studies of male golden-collared manakins, Manacus vitellinus, a small bird of the Neotropics with a physically intense and noisy courtship display, have uncovered numerous androgen-dependent neuromuscular and metabolic specializations that enable not only the performance of elaborate courtship routines, but also their evolutionary exaggeration. However, physiological specializations for one function can create limits on their use for other purposes. Such trade-offs may influence the way courtship develops but may also provide information used by females for mate choice. We review this body of work with an eye towards expanding our appreciation of the evolution of widespread tissue hormone sensitivity and hormone action as the system through which elaborate courtship behaviours evolve.
Objectives:
The aim of our study was to compare morphometric patterns of facial sexual dimorphism with strength-face relationship in members of two distinct populations of European and Central Asian origin: Russians and Tuvans.
Methods:
Handgrip strength (HGS) measures and facial photographs were collected from Russian (n = 233) and Tuvan (n = 187) men and women. We digitized 70 landmarks and semilandmarks on full-face and 54 landmarks and semilandmarks on profile photos. This was done to capture variation in facial morphology. After that, we performed the shape regressions of landmarks' coordinates upon sex and HGS. Results were visualized in forms of thin-plate deformation grids and geometric morphometric morphs.
Results:
In both populations, HGS was associated significantly with male facial shape only. In Russian men, strength-related changes of facial shape were almost completely in direction of increase in male-typicality. This was especially evident for the relative lower facial width, which was higher in men compared to women, as well as in stronger men compared to weaker ones. On the contrary, in Tuvans the lower face was relatively narrower in men than in women. However, the facial shape of strong Tuvan men was also associated with relatively wider lower face. Our results indicate that the effect of strength on facial shape is relatively independent of facial sexual dimorphism.
Conclusions:
Our findings clearly demonstrate that physical strength is associated with the shape of the lower part of male faces even in populations with a mismatched direction of lower face sexual dimorphism.
Dünya fiziksel anlamda olağan hızında dönmeye devam ederken, toplumsal olarak olağanüstü bir dönüşüm yaşıyor. İnsanoğlunun diğer canlılara bir şekilde üstünlük kurmasını sağlayan ortak hareket etmeye dayalı kültür de bu dönüşümün merkezinde yer alıyor. Her geçen gün kültürün bireylere dayattıklarına eleştiri, daha özgür, daha eşit bir dünya arayışı çerçevesinde değerlendirilebilecek yeni düşünceler ortaya çıkıyor. Yeni bir düşünce olmamakla birlikte bugün halen sıcaklığını koruyan feminist bakış açısı: olay-durum veya olgulara özünde cinsiyet eşitsizliğinin yarattığı gerçekleri arama teziyle eleştirel bir bakış açısı sunuyor. Feminist çerçeveden bakılınca bütün memelilerin varlıklarını devam etmelerinin bir gereği olarak cinsiyetli olmanın kadınlar aleyhine işlemesi ve erkeklere liderlik konumları için avantaj sağlaması üzerinde durulması gereken bir konudur. Liderliğe evrimsel bir bakış açısıyla bakıldığında dış tehditlerin yüksek olduğu ilkel topluluklarda otokratik-kas gücü yüksek-agresif kişilerin lider olarak seçildiği, dış tehditlerin zamanla azalıp grup içi dayanışmanın öne çıkmasıyla en zayıf olanında hakkını gözetecek daha demokratik kişilerin lider olarak tercih edildiği anlaşılmaktadır. Buradan hareketle kadın veya kadınsı özelliklerin öne çıkmasını gelişmişliğin bir göstergesi, medeniyetin bir ölçüsü olarak kabul etmek yanlış olmayacaktır. Türkiye Cumhuriyeti’nin 100. yılına girildiği ve gelecek 100 yılların konuşulduğu bu günlerde toplumsal yaşamın hemen bütün boyutlarında cinsiyet eşitliği üzerine düşünmek yerinde olacaktır.
Esta tesis doctoral responde al interés de comprender el papel de la energía en las relaciones entre el ser humano y su entorno, siendo la energía la que modela y ajusta las adaptaciones biológicas y conductuales de los organismos terrestres y, por extensión, de la especie humana.
Son varios los estudios dentro de la ecología del comportamiento humano que han utilizado la energía para comprender la adaptación y la adaptabilidad humana. Dicha adaptabilidad es fruto de la flexibilidad que muestra nuestra especie, adquirida gracias a la prolongada inmadurez de Homo sapiens. Sin embargo, son menores los estudios que se han centrado en comprender cómo actúa la energía en la conducta y la biología de los individuos subadultos. Por ello, el principal interés de esta investigación es estudiar cómo afecta la energía a la puesta en marcha de diferentes actividades de subsistencia imprescindibles en los grupos de cazadores y recolectores. Concretamente, se evaluará si el inicio de la división de labores por sexo se explica en base a diferencias en el coste y la eficiencia energética de los distintos individuos. Así mismo, se valorará el papel activo y la productividad de los individuos subadultos dentro de un grupo humano, y si ello se ve limitado por cuestiones energéticas. Finalmente, se analizará si el coste de la locomoción y la velocidad óptima alcanzada por sujetos subadultos puede limitar la movilidad y la puesta en marcha de actividades que dependen de la locomoción en grupos humanos. Con todo, se tratará de conocer si la energía actúa como un limitante a la hora de aprender y desarrollar actividades complejas propias de nuestra especie y cómo afecta esto a las dinámicas energéticas del resto de individuos de un grupo humano.
Para ello se han empleado datos de dos estudios experimentales, llevados a cabo en el Laboratorio de Bioenergía y Análisis del Movimiento del Centro Nacional de Investigación sobre la Evolución Humana (CENIEH). Estos corresponden a 118 voluntarios de entre 7 y 14 años de edad, y recogen diferentes medidas antropométricas, de composición corporal y de gasto energético. Los dos estudios experimentales incluían simulaciones de actividades comunes entre los individuos subadultos de ciertos grupos de cazadores y recolectores de la actualidad, como la recolección y la extracción de recursos y caminar a diferentes velocidades.
Los resultados obtenidos en el conjunto de las pruebas revelan que, tanto la energía gastada, como la eficiencia en una actividad productiva, no explican la diferencia de labores entre sexos, pero tampoco entre edades si se comparan con las velocidades óptimas adultas. Se propone que la división de labores en base al sexo debe responder a otras cuestiones, relacionadas con el aprendizaje temprano en habilidades complejas específicas para cada sexo. Además, debido a la relación entre el gasto energético y el tamaño corporal en actividades productivas en las que se aprenden esas habilidades, los individuos juveniles gozan de una ventaja, ya que comienzan a aprender en una fase en la que el crecimiento corporal se retiene y se consume menos energía porque se tiene un tamaño menor. Por ello, practicar durante esta etapa, supone un ahorro en forma de energía respecto a otras fases en las que se tiene un mayor tamaño corporal y sí se invierte más energía en crecimiento y desarrollo, como en la adolescencia. Por otro lado, el gasto energético de la prueba de extracción de recursos bien se cubriría con el retorno calórico facilitado por diferentes autores, pero no podríamos confirmar que se alcancen ya tasas de productividad adulta. En esta prueba también se ha demostrado que, igual que se observa en el gasto energético del resto de actividades aquí desarrolladas, tampoco existen diferencias entre sexos en la eficiencia derivada de extraer recursos del suelo. Este resultado se ha obtenido al tener en cuenta la tasa de eficiencia (energía gastada/retorno conseguido). Respecto a las actividades que dependen de la locomoción bípeda, no existen diferencias entre sexos en la velocidad óptima, ni el gasto derivado de alcanzar esta velocidad. Por lo tanto, se propone que ambas variables no condicionarían a los individuos aquí estudiados a la hora de acompañar a un grupo adulto de cazadores y recolectores, ni durante la movilidad ni mientras se captan recursos. Por otro lado, la capacidad para alcanzar velocidades óptimas semejantes a las publicadas para individuos adultos, podría suponer a los subadultos ventajas al consumir menos energía por ser más pequeños. No obstante, en determinadas sociedades estos individuos no se involucran en ciertas actividades de manera temprana, por lo que existen otras causas, más allá de la velocidad o el gasto energético, que pueden dificultar la participación de los subadultos en algunas actividades adultas.
Todas estas ventajas han podido propiciar en la especie Homo sapiens un ahorro de energía que directamente, no solo beneficia al individuo subadulto, sino también a otros individuos del grupo. Muchas de las ventajas aquí expuestas se ven acompasadas por la peculiar historia biológica humana. Por ello, otras especies de homininos que hayan requerido del aprendizaje de habilidades complejas para subsistir, se habrían beneficiado de las mismas ventajas que exponemos en esta investigación, solo si hubiesen tenido los mismos patrones de desarrollo y crecimiento encontrados en Homo sapiens.
The main interest of this Ph.D. Dissertation is to understand the key-role of the energy in the relationship between humans and the environment, since energy is the factor that models and adjusts the biological and behavioural adaptations of all living organisms and, by extension, of humans too.
Several studies within the Human Behavioural Ecology have used the energy to understand human adaptation and adaptability. This adaptability is the main result of human plasticity, acquired thanks to the prolonged immaturity of Homo sapiens. However, fewer studies have focused on understanding how energy affects subadult behaviour and biology. Therefore, the main interest of this research is to study how energy affects the implementation of different essential human behaviours in hunter-gatherer societies. Specifically, it will be evaluated if the onset of division of labour by sex is caused by differences in the efficiency and the energetic demands of different individuals. In addition, the active role and the productivity of non-adult individuals will be assessed, together with possible energetic limitations in this regard. Finally, the cost of locomotion and the optimal speed will be analysed to test if non-adult individuals limit group mobility or the participation in foraging activities involving locomotion. Consequently, it will be discussed if energy is a limitation while learning-by-doing complex activities, commonly practiced by Homo sapiens species, and how this affects the energetic dynamics of a human group.
To achieve this, data from two experimental studies carried out in the Laboratory of Bioenergy and Analysis of the Movement of the CENIEH have been used. Data were obtained from 118 volunteers between 7 and 14 years of age, and referred to different anthropometric, body composition and energy expenditure measurements. The two experimental studies consisted of three trials, simulating common activities among subadult individuals of certain groups of current hunter-gatherers. The recreated activities were a gathering test, a digging tubers trial, and a locomotion activity at different speeds.
The results obtained in all of the experimental studies reveal that the energy
expended and the efficiency in a productive activity do not explain the onset of sex division of labor. It is proposed that the division of labor is caused by other questions related to the early learning in sex-specific complex skills. In addition, due to the relationship between energy expenditure and body size in some productive activities (through which non-adults learn these skills), juvenile individuals have an energetic advantage, because they decelerate the body growth in this phase and they consume less energy due to their smaller body size. Therefore, learning-by-doing at this stage promotes energy savings compared to other phases with a larger body size and a greater somatic investment, like adolescence.
On the other hand, the energy expenditure of digging would be covered with the energetic return reported by other investigations, but we cannot confirm that our individuals have already achieved adult productivity rates. In this test, taking into account the results of the efficiency index (energy expended/items reported) it has also been shown that there are no differences among sexes based on the efficiency of extracting tubers from the ground, as we have observed for the energy expenditure of the rest of the activities carried out here.
Regarding the locomotion test, there are no differences among sexes, or ages when compared with adult values from other studies, neither comparing the optimal walking speed, nor the energy expenditure at this speed. Thus, it is proposed that both variables are not a limitation for the individuals here studied if they would be part of a hunter-gatherer group, neither during the mobility of the group, nor while foraging.
On the other hand, our volunteers reach similar optimal speeds as those reported in the literature for adult individuals. This could constitute and advantage for non-adult individuals, as they are consuming less energy because they are smaller. Nonetheless, in certain societies, non-adult individuals are not involved in some activities anyway, thus there may be other causes, beyond speed or energy costs, that can hinder the
participation of non-adults in some adult activities.
All the mentioned advantages would allow energy savings for Homo sapiens. This savings would directly benefit the non-adult individual, but also the rest of the group. However, most of the advantages highlighted here are linked to the peculiar Homo sapiens Life History. Therefore, the advantages we expose in this research would benefit other extinct species with subsistence complex skills, only if Homo sapiens-like development and growth patterns were already present.
Nuzzo, JL. Narrative review of sex differences in muscle strength, endurance, activation, size, fiber type, and strength training participation rates, preferences, motivations, injuries, and neuromuscular adaptations. J Strength Cond Res 37(2): 494-536, 2023-Biological sex and its relation with exercise participation and sports performance continue to be discussed. Here, the purpose was to inform such discussions by summarizing the literature on sex differences in numerous strength training-related variables and outcomes-muscle strength and endurance, muscle mass and size, muscle fiber type, muscle twitch forces, and voluntary activation; strength training participation rates, motivations, preferences, and practices; and injuries and changes in muscle size and strength with strength training. Male subjects become notably stronger than female subjects around age 15 years. In adults, sex differences in strength are more pronounced in upper-body than lower-body muscles and in concentric than eccentric contractions. Greater male than female strength is not because of higher voluntary activation but to greater muscle mass and type II fiber areas. Men participate in strength training more frequently than women. Men are motivated more by challenge, competition, social recognition, and a desire to increase muscle size and strength. Men also have greater preference for competitive, high-intensity, and upper-body exercise. Women are motivated more by improved attractiveness, muscle "toning," and body mass management. Women have greater preference for supervised and lower-body exercise. Intrasexual competition, mate selection, and the drive for muscularity are likely fundamental causes of exercise behaviors in men and women. Men and women increase muscle size and strength after weeks of strength training, but women experience greater relative strength improvements depending on age and muscle group. Men exhibit higher strength training injury rates. No sex difference exists in strength loss and muscle soreness after muscle-damaging exercise.
This chapter focuses on the behaviors employed by men in the service of attracting mates, which we discuss as having emerged to solve specific reproductive problems faced by women. We consider behaviors employed by men to attract mates in short-term mating and long-term mating contexts, given the differential valuation on certain behavioral repertoire that emerge. In short-term mating, we specifically consider behavioral displays of dominance with their dispositional and situational antecedents before discussing men’s pursuit of distinctiveness and humor use, behaviors ostensibly indicative of good genes. In long-term mating, our discussion centers around the desirability of different resource displays and benevolence. We further discuss cues ostensibly diagnostic of paternal investment ability and an interest in monogamy. Our final section addresses how modern mating markets present adaptive problems for men (e.g., online dating, appearance enhancing behaviors) and how men seek to solve the new problems that have emerged.
Evolutionary psychiatry attempts to explain and examine the development and prevalence of psychiatric disorders through the lens of evolutionary and adaptationist theories. In this edited volume, leading international evolutionary scholars present a variety of Darwinian perspectives that will encourage readers to consider 'why' as well as 'how' mental disorders arise. Using insights from comparative animal evolution, ethology, anthropology, culture, philosophy and other humanities, evolutionary thinking helps us to re-evaluate psychiatric epidemiology, genetics, biochemistry and psychology. It seeks explanations for persistent heritable traits shaped by selection and other evolutionary processes, and reviews traits and disorders using phylogenetic history and insights from the neurosciences as well as the effects of the modern environment. By bridging the gap between social and biological approaches to psychiatry, and encouraging bringing the evolutionary perspective into mainstream psychiatry, this book will help to inspire new avenues of research into the causation and treatment of mental disorders.
Background
Environmental exposures in early life explain variability in many physiological and behavioural traits in adulthood. Recently, we showed that exposure to a composite marker of low maternal capital explained the clustering of adverse behavioural and physical traits in adult daughters in a Brazilian birth cohort. These associations were strongly mediated by whether or not the daughter had reproduced by the age of 18 years. Using evolutionary life history theory, we attributed these associations to trade-offs between competing outcomes, whereby daughters exposed to low maternal capital prioritised investment in reproduction and defence over maintenance and growth. However, little is known about such trade-offs in sons.
Methods
We investigated 2,024 mother–son dyads from the same birth cohort. We combined data on maternal height, body mass index, income, and education into a composite “maternal capital” index. Son outcomes included reproductive status at the age of 18 years, growth trajectory, adult anthropometry, body composition, cardio-metabolic risk, educational attainment, work status, and risky behaviour (smoking, violent crime). We tested whether sons' early reproduction and exposure to low maternal capital were associated with adverse outcomes and whether this accounted for the clustering of adverse outcomes within individuals.
Results
Sons reproducing early were shorter, less educated, and more likely to be earning a salary and showing risky behaviour compared to those not reproducing, but did not differ in foetal growth. Low maternal capital was associated with a greater likelihood of sons' reproducing early, leaving school, and smoking. High maternal capital was positively associated with sons' birth weight, adult size, and staying in school. However, the greater adiposity of high-capital sons was associated with an unhealthier cardio-metabolic profile.
Conclusion
Exposure to low maternal investment is associated with trade-offs between life history functions, helping to explain the clustering of adverse outcomes in sons. The patterns indicated future discounting, with reduced maternal investment associated with early reproduction but less investment in growth, education, or healthy behaviour. However, we also found differences compared to our analyses of daughters, with fewer physical costs associated with early reproduction. Exposure to intergenerational “cycles of disadvantage” has different effects on sons vs. daughters, hence interventions may have sex-specific consequences.
Individuals infer men's formidability through various facial and bodily features. Such inferences covary with perceptions of men's personalities and motivational states, potentially informing subsequent affiliative decisions. Within these inferences could be an implicit understanding of men's preferred humor styles. Across four studies, this research considered perceptions of men's proclivity to employ four humor styles through different formidability cues: upper body strength (Study 1), muscularity (Study 2), facial width-to-height ratio (Study 3), and neck musculature (Study 4). A relatively consistent perception emerged of formidable men as more likely to use aggressive humor. Conversely, an absence of formidability cues elicited perceptions of increased likelihood to use self-defeating humor. We interpret results from an evolutionary perspective for how individuals can identify behavioral strategies through morphological features.
Selecting formidable male coalitions to navigate intergroup threats and resource acquisition evolved to enhance survival through group living, given men's enhanced ability to extract and protect resources through physical aggression. Though advantageous in certain contexts, formidable men can nonetheless inflict intragroup costs, suggesting
preferences for this trait varies with resource availability in local ecologies. This study tasked participants (477 women, 140 men; MAge = 19.98, SD = 4.22) with building coalitions from arrays of physically strong and weak men to acquire resources in hopeful and desperate ecologies before assessing endorsement of several aspects of conservatism. Individuals high in social dominance orientation reported greater aversion to physically strong men in desperate ecologies, although strength was generally preferred independent of ideological differences. Results suggest a tradeoffs framework in coalition-building based on the inferred costs and benefits of physically strong allies.
Men experience elevated rates of various mental health issues including suicide, substance use disorder and attention-deficit hyperactivity disorder, as well as lower rates of mental health service utilization. Moreover, men and boys are experiencing increasing difficulties in sectors such as education and employment, with increased risk of low educational attainment and failure to launch. Such difficulties are sometimes narrowly explained with reference to a singular concept – masculinity – without exercising any peripheral vision to examine social context and population-level factors. This narrow approach has tended to unduly dominate the conversation about men’s mental health, and can also verge on victim blaming the affected men. This chapter argues for change, namely, the adoption of a novel public-health inspired approach to men’s mental health, with a focus on distal and proximal social determinants. Such change would involve moving beyond a narrow one-dimensional focus on the concept of masculinity, and would instead focus on population-level factors that negatively affect men’s mental health including: (i) harmful stereotypes of men; (ii) the gender empathy gap; and (iii) male gender blindness. These three concepts are described and illuminated with reference to various examples, including male victims of intimate partner violence, and recent discussions about gender and COVID-19.
Facial expressions are important social communicators. In addition to communicating social information, the specific muscular movements of expressions may serve additional functional roles. For example, recalibration theory hypothesizes that the anger expression exaggerates facial cues of strength, an indicator of human fighting ability, to increase bargaining power in conflicts. Supporting this theory is evidence that faces displaying one element of an angry expression (e.g. lowered eyebrows) are perceived to be stronger than faces with opposite expression features (e.g. raised eyebrows for fear). The present study sought stronger evidence that more natural manipulations of facial anger also enhance perceived strength. We used expression aftereffects to bias perception of a neutral face towards anger and observed the effects on perceptions of strength. In addition, we tested the specificity of the strength-cue enhancing effect by examining whether two other expressions, fear and happy, also affected perceptions of strength. We found that, as predicted, a face biased to be perceived as angrier was rated as stronger compared to a baseline rating, whereas a face biased to be more fearful was rated as weaker, consistent with the purported function of fear as an act of submission. Interestingly, faces biased towards a happy expression were also perceived as stronger, though the effect was smaller than that for anger. Overall, the results supported the recalibration theory hypothesis that the anger expression enhances cues of strength to increase bargaining power in conflicts, but with some limitations regarding the specificity of the function to anger.
In most social species, position in the male social hierarchy and reproductive success are positively correlated; in humans, however, this relationship is less clear, with studies of traditional societies yielding mixed results. In the most economically advanced human populations, the adaptiveness of status vanishes altogether; social status and fertility are uncorrelated. These findings have been interpreted to suggest that evolutionary principles may not be appropriate for the explanation of human behavior, especially in modern environments. The present study tests the adaptiveness of social status with actual mating and reproductive data in a representative sample of males from an industrial society. Reproductive success, even when assessed by a more reliable measure of actual male fertility than the one commonly used, fails to correlate with social status. In striking contrast, however, status is found to be highly correlated with potential fertility, as estimated from copulation frequency. Status thus accounts for as much as 62% of the variance in this proximate component of fitness. This pattern is remarkably similar to what is found in many traditional societies and would result in a substantial positive relationship between cultural and reproductive success in industrial populations were it not for the novel conditions imposed by contraception and monogamy. Various underlying mechanisms are suggested for these findings, illustrating the value of current behavioral and reproductive data in the study of adaptation. It is concluded that evolutionary explanations of human behavior remain entirely relevant in modern societies.
Human physical attractiveness appears to be an important signal of mate value that is utilized in mate choice We argue that performance-related physical fitness (PF) was an important facet of ancestral male mate value and, therefore, that a positive relationship exists between PF and physical attractiveness as well as mating success. We investigated these relationships in a sample of 80 young men. In line with our predictions, we found that (i) a composite measure of PF correlated substantially with body attractiveness (r=.43, after controlling for confounds) but not with facial attractiveness; (ii) PF was positively related to various measures of self-reported mating success (rS ≈ .22); (iii) the relationship between PF and self-reported mating success was partly mediated by body attractiveness. We conclude it is a key function of men's body attractiveness to signal their PF and that men's faces and bodies signal different facets of mate value.
Models of sexual selection typically assume a cost to the production and maintenance of sexually selected traits. However, within a population, individuals of high phenotypic quality may not only show greater expression of the trait but may also have higher survival rates. In such a case, the true cost of the trait may be difficult to detect. Comparative studies can circumvent some of the difficulties inherent in intraspecific studies. In this study, I used a comparative approach to examine the relation between sexual size dimorphism and adult mortality in natural populations of mammals. After controlling for the effects of phylogeny, I found that the degree of male-bias in adult mortality was positively correlated with the degree of sexual size dimorphism across taxa. This is the first comparative evidence for a cost of sexually selected traits in natural populations of mammals. In contrast to the general rule that mortality in mammals is male-biased, I also found that it is frequently female-biased in monogamous taxa of mammals. I suggest that in monogamous species the cost of reproduction to females will be similar to that of polygynous species. However, males of monogamous species will be spared the costs of male-male competition and dimorphic growth. This decrease in male costs relative to females may then lead to a female-bias in mortality.
According to current evolutionary theory, advertising traits that honestly indicate an organism's genetic quality might be costly to produce or maintain, though the kind of costs involved in this process are controversial. Recently the immunocompetence hypothesis has proposed that testosterone (T) stimulates the expression of male sexually selected traits while decreasing im- munocompetence. Even though some recent studies have shown an effect of T on ectoparasite load, the dual effect of the hormone has not been addressed in free-living populations. Here we report results of an experiment in a free-living population of the lizard Psammodromus algirus during the mating season. Males implanted with T had larger patches of breeding color and behaved more aggressively than control males. In T-implanted males, the increase in number of ticks during the mating season was significantly higher than in control males and this negatively affected several hematological parameters. T-males suffered significantly higher mortality than control males during the experiment The results from the manipulation of T are consistent with the dual effect of this hormone. Key words: parasites, Psammodromus algirus, secondary sexual characters, tes- tosterone. (BehavEcol 7:145-150 (1996))
We examined the hypothesis that increased aggression results in decreased survivorship. We tested this hypothesis by increasing aggression of free-living male lizards Sceloporus jarrovi with testosterone implants and evaluating the effects on survivorship. A previous study showed that testosterone-implanted males were more aggressive than controls, suggesting a greater degree of success in male-male competition. Results of the present study show that the same testosterone-implanted lizards experienced greater mortality. Testosterone-treated males were also seen more frequently and more conspicuous ones were less likely to survive. Testosterone-treated males lost more weight over the summer. In controls, survivorship was negatively correlated with the body weight index. These data suggest that conspicuousness and energetic demands interact in their influence on survivorship. Thus, the natural plasma level of testosterone may be at an optimal level balancing any potential selection pressures for a higher level of testosterone through sexual selection with selection pressures for a lower level through a decrease in survivorship.
It has been argued that females should be able to choose parasite-resistant mates on the basis of the quality of male secondary sexual characters and that such signals must be costly handicaps in order to evolve. To a large extent, handicap hypotheses have relied on energetic explanations for these costs. Here, we have presented a phenomenological model, operating on an intraspecific level, which views the cost of secondary sexual development from an endocrinological perspective. The primary androgenic hormone, testosterone, has a dualistic effect; it stimulates development of characteristics used in sexual selection while reducing immunocompetence. This "double-edged sword" creates a physiological trade-off that influences and is influenced by parasite burden. We propose a negative-feedback loop between signal intensity and parasite burden by suggesting that testosterone-dependent signal intensity is a plastic response. This response is modified in accordance with the competing demands of the potential costs of parasite infection versus that of increased reproductive success afforded by exaggerated signals. We clarify how this trade-off is intimately involved in the evolution of secondary sexual characteristics and how it may explain some of the equivocal empirical results that have surfaced in attempts to quantify parasite's effect on sexual selection.
Energy expenditure varies among people, independent of body size and composition, and persons with a "low" metabolic rate seem to be at higher risk of gaining weight. To assess the importance of skeletal muscle metabolism as a determinant of metabolic rate, 24-h energy expenditure, basal metabolic rate (BMR), and sleeping metabolic rate (SMR) were measured by indirect calorimetry in 14 subjects (7 males, 7 females; 30 +/- 6 yr [mean +/- SD]; 79.1 +/- 17.3 kg; 22 +/- 7% body fat), and compared to forearm oxygen uptake. Values of energy expenditure were adjusted for individual differences in fat-free mass, fat mass, age, and sex. Adjusted BMR and SMR, expressed as deviations from predicted values, correlated with forearm resting oxygen uptake (ml O2/liter forearm) (r = 0.72, P less than 0.005 and r = 0.53, P = 0.05, respectively). These findings suggest that differences in resting muscle metabolism account for part of the variance in metabolic rate among individuals and may play a role in the pathogenesis of obesity.
Sumario: The purposes of the present study were: (1) to determine the magnitude of the sex difference in upper and lower-body strenght in groups of men and women with similar physical activity backgrounds and (2) to determine the extent to which the sex difference in strenght is explained by differences in FFW and FFCSA. By deduction, the portion of the sex difference in strength not acounted for by FFW and FFCSA could be attributed to neuromuscular and/or other factors
This study examined possible gender differences for relative upper (elbow) to lower (knee) body strength and endurance, as well as relative flexion to extension strength and endurance. Seven women and nine men who were matched for both upper and lower body aerobic power were tested on an isokinetic strength instrument. Absolute isokinetic strength was lower (P<0-01) for the women than the men for all measurements. When strength was expressed per lean body weight, the women were weaker (P<005) only for elbow flexion strength. The women had a lower (P<005) upper to lower body strength ratio for flexion, but not for extension. There were also no differences (P>005) in isokinetic endurance fatigue decrements, or upper to lower body endurance ratios between genders. These data indicated that there were differences in absolute strength between the genders, but strength per lean body weight, as well as upper to lower body ratios for strength and endurance were similar for both genders. It was recommended that aerobic fitness and level of training be taken into account when strength and endurance were compared between the genders.
To date, there have been very few studies on the age dependence of maximal isometric muscle strength (MIMS) in healthy subjects aged 20-80 years, based upon measurements of a large number of functional muscle groups (FMGs). Using a hand-held pull gauge it is possible to measure MIMS of nearly every FMG. The objectives of this study were to obtain normative values for MIMS, to evaluate differences in MIMS in relation to gender and body side and to compare the age dependence of muscle strength between women and men. In a convenience sample of 290 healthy women (aged 20-82 years) and 253 men (aged 21-79 years), MIMS of 51 FMGs was measured. For each FMG the age dependence of MIMS was depicted, side and gender specific, as percentile curves and was analysed using linear quantile regression analysis. MIMS was found to be significantly higher in men than in women and higher on the right than on the left side. A biphasic model with linear equations for strength medians was derived for each gender. The age at transition from phase 1 to phase 2 was 55 years (SD 8) for women and 49 years (SD 13) for men. During phase 1, MIMS did not decrease significantly. During phase 2, MIMS decreased in all FMGs in both genders with a steeper slope in women (-0.92) than in men (-0.63). The age dependence of MIMS differed significantly between women and men. The present study gives gender-specific equations which enable one to calculate normative values for MIMS, as measured with a pull gauge, based upon age. These normative values will allow an objective assessment of patients with diminished muscle strength as, for example, in myositis, rheumatoid arthritis and nerve root compression syndromes or in the elderly.
Sexually selected traits provide a mating advantage to the bearer but they should also exact a cost through natural selection. Whereas the mating benefits from such traits have been well documented, the costs have been difficult to demonstrate. In this analysis of mortality patterns across 28 North American passerine bird species, we show that sex-biased mortality (log1o male mortality - log1o female mortality) is positively correlated with both sexual size dimorphism and male plumage brightness. Male (but not female) mortality is positively correlated with sexual size dimorphism, suggesting a cost to male-male competition. Female (but not male) mortality is negatively correlated with male brightness, and we argue from this that the evolution of male brightness has been constrained by mortality costs. Thus sexual dimorphism in body size and plumage colour within bird species appears to be influenced by the opposing forces of sexual selection, acting to increase dimorphism, and adult mortality rates, which constrain the evolution of these traits. Differences in the expression of ornamental traits across species may be explained not only by variation in the mating benefits that accrue from ornaments, as is so often assumed, but also by variation in the costs of these traits.
Recent advances in human life history theory have provided new insights into the potential selection pressures that were instrumental in the evolution of human and non-human primate males. However, gaps remain in our understanding of how primate males regulate and allocate energetic resources between survivorship and reproductive effort. Defense against parasitic infection is an important force shaping life history evolution. Proper performance of immunological responses against infection is influenced by many physiological systems, including metabolic, reproductive, and stress hormones. Because androgens influence and modulate immune, reproduc-tive, and somatic metabolic functions, assessing changes in testosterone and immune factors during infection may yield insight into male physiological ecology. In this review, we examine male life history trade-offs between immune and reproductive endocrine functions as well as provide a comprehensive review of testosterone–immunocompetence relationships. Emphasis is placed on testosterone because it is a primary hormone shown to be crucial to energy-allocation processes in vertebrates. Non-primate species have been used more extensively in this research than humans or non-human primates, and therefore this extensive literature is organized and reviewed in order to better understand potential parallel relationships in primates, especially humans. Furthermore, we attempt to reconcile the many inconsistent results obtained from field studies on immune–endo-crine interactions as well as detail various methodologies that may be used to forward this research in evolutionary anthropology. Am.
Recent advances in human life history theory have provided new insights into the potential selection pressures that were instrumental in the evolution of human and non-human primate males. However, gaps remain in our understanding of how primate males regulate and allocate energetic resources between survivorship and reproductive effort. Defense against parasitic infection is an important force shaping life history evolution. Proper performance of immunological responses against infection is influenced by many physiological systems, including metabolic, reproductive, and stress hormones. Because androgens influence and modulate immune, reproduc-tive, and somatic metabolic functions, assessing changes in testosterone and immune factors during infection may yield insight into male physiological ecology. In this review, we examine male life history trade-offs between immune and reproductive endocrine functions as well as provide a comprehensive review of testosterone–immunocompetence relationships. Emphasis is placed on testosterone because it is a primary hormone shown to be crucial to energy-allocation processes in vertebrates. Non-primate species have been used more extensively in this research than humans or non-human primates, and therefore this extensive literature is organized and reviewed in order to better understand potential parallel relationships in primates, especially humans. Furthermore, we attempt to reconcile the many inconsistent results obtained from field studies on immune–endo-crine interactions as well as detail various methodologies that may be used to forward this research in evolutionary anthropology. Am.
Handgrip strength (HGS) is a noninvasive measure of physical health that is negatively correlated with disability, morbidity, and mortality rates in adults. Highly heritable, HGS is indicative of blood testosterone levels and levels of fat-free body mass. In this study, we investigated whether HGS was related to measures of body morphology [shoulder-to-hip ratio (SHR), waist-to-hip ratio, and second-digit-to-fourth-digit ratio (2D:4D)], aggressive behavior, and sexual history in 82 male and 61 female college students. Results showed that HGS was correlated with SHRs, aggressive behavior, age at first sexual intercourse, and promiscuity in males but not in females. HGS appears to be an honest signal for genetic quality in males.
Upper-body fat has negative effects and lower-body fat has positive effects on the supply of long-chain polyunsaturated fatty acids that are essential for neurodevelopment. Thus, waist-hip ratio (WHR), a useful proxy for the ratio of upper-body fat to lower-body fat, should predict cognitive ability in women and their offspring. Moreover, because teenage mothers and their children compete for these resources, their cognitive development should be compromised, but less so for mothers with lower WHRs. These predictions are supported by data from the Third National Health and Nutrition Examination Survey. Controlling for other correlates of cognitive ability, women with lower WHRs and their children have significantly higher cognitive test scores, and teenage mothers with lower WHRs and their children are protected from cognitive decrements associated with teen births. These findings support the idea that WHR reflects the availability of neurodevelopmental resources and thus offer a new explanation for men's preference for low WHR.
BACKGROUND
Prostate cancer and benign prostatic hyperplasia are important age-related prostatic diseases that are under the influence of testicular hormones. However, the disparity between male and female life expectancy within the human population cannot be explained solely by the prevalence of prostatic disease-related mortality. The purpose of this paper is to explore the possibility that the testis exerts a detrimental effect on life span.METHODS
First, we review previously published and unpublished data on the influence of the testis on the life span of dogs and men. Aging in pet dogs and men is then discussed in terms of evolutionary theory, emphasizing the significance of a prolonged postreproductive life span and possible consequences of late-acting deleterious genes in these two species. Finally, we present preliminary data that orchiectomy can reduce DNA damage within the brain of elderly male dogs.RESULTS AND CONCLUSIONS
Taken together, these observations raise the intriguing possibility that interventions to antagonize the testis might have much broader therapeutic applications that will extend well beyond the treatment of prostate cancer. Prostate 43:272–277, 2000. © 2000 Wiley-Liss, Inc.
Males generally exhibit reduced immune responses as well as increased intensity and prevalence of infections compared to female conspecifics. Physiologically, these sex differences may reflect the immunosuppressive effects of androgens. In addition to suppressing immune function, androgens maintain several characteristics important for reproductive success. Thus, a dynamic relationship is assumed to exist among hormones, secondary sex traits, and the immune system. Ultimately, the extent to which this relationship exists may be related to the mating system. Because polygynous males generally have higher circulating testosterone concentrations and rely more heavily on testosterone-dependent traits for reproductive success than monogamous males, sex differences in immune function are hypothesised to be more pronounced among polygynous as compared to monogamous species. Additionally, if secondary sex traits are used to advertise infection status, then females should be able to use the condition of male secondary sex traits to discern the immune/infection status of males during mate selection. The purpose of this review is to survey current studies that examine both the proximate mechanisms and ultimate function of variation in immune function and susceptibility to infection and determine whether immunological variation influences mate preference and possibly reproductive success.
Opinions vary but one interpretation of the vastly expanded hominid postcranial sample from 4 to 1·3 M.Y. hominids leads to the following working hypotheses: (1) The average female of the earliest known species of Hominidae, Australopithecus afarensis, weighed about 29 kg and the male, 45 kg. (2) Average female body weight remains between 29 and 34 kg in all species of hominids before the appearance of Homo erectus at 1·7 M.Y. (3) Average male body weight ranged between 40 and 52 kg in these pre-erectus species. (4) The origin of H. erectus marked a dramatic increase in body size especially in the female. (5) The brain size increase from A. afarensis to A. africanus to the "robust" australopithecines does not appear to be an artifact of body size increase but reflects progressive encephalization. (6) The expansion of absolute brain size with the appearance of Homo is beyond what would be expected from body size increase alone. These working hypotheses have implications for how members of early hominid species behaved to enhance their chances of survival and reproduction within the constraints and requirements of their environments. For example, the relatively high level of body size sexual dimorphism in the earliest species implies a polygynous mating system and a ranging pattern in which females foraged in smaller territories than the males. Although one might expect from analogy with Pan to have social groups consisting of closely related males and less closely related females, the high level of sexual dimorphism is not expected. Perhaps the substantial body size increase and reduction in sexual dimorphism apparent in Homo by 1·7 M.Y. is related to a significant expansion in ranging area. The energetic requirement of the expanded brain may imply altered feeding strategies in both the "robust" australopithecine and Homo lineages.
Physical competition is widespread in human societies. Because performance in competitive sports can signal phenotypic quality and fighting ability, high level performance, especially on the part of men, is likely to be attractive to the opposite sex. We investigated the relationship between involvement in competitive sport and self-reported numbers of sexual partners. Both male and female students who compete in sports reported significantly higher numbers of partners than other students, and within the athletes, higher levels of performance predicted more partners. Among men, body mass index (BMI) and educational level also had significant effects. We discuss possible implications for the evolution of competitive sport, ritual fighting behavior, and the persistence of left-handedness.
The immunocompetence handicap hypothesis was formulated 12 years ago in an attempt to offer a proximate mechanism by which female choice of males could be explained by endocrine control of honest signalling. The hypothesis suggested that testosterone has a dual effect in males of controlling the development of sexual signals while causing immunosuppression. Our purpose in this review is to examine the empirical evidence to date that has attempted to test the hypothesis, and to conduct a meta-analysis on two of the assumptions of the hypothesis, that testosterone reduces immunocompetence and increases parasitism, to ascertain any statistical trend in the data. There is some evidence to suggest that testosterone is responsible for the magnitude of trait expression or development of sexual traits, but this is by no means conclusive. The results of many studies attempting to find evidence for the supposed immunosuppressive qualities of testosterone are difficult to interpret since they are observational rather than experimental. Of the experimental studies, the data obtained are ambiguous, and this is reflected in the result of the meta-analysis. Overall, the meta-analysis found a significant suppressive effect of testosterone on immunity, in support of the hypothesis, but this effect disappeared when we controlled for multiple studies on the same species. There was no effect of testosterone on direct measures of immunity, but it did increase ectoparasite abundance in several studies, in particular in reptiles. A funnel analysis indicated that the results were robust to a publication bias. Alternative substances that interact with testosterone, such as glucocorticoids, may be important. Ultimately, a greater understanding is required of the complex relationships that exist both within and between the endocrine and immune systems and their consequences for mate choice decision making.
The efficacy of a 10-week program of circuit weight training to elicit specific physiological alterations was evaluated in a group of men (n = 16) and a group of women (n = 12), with an additional group of men (n = 10) and a group of women (n = 11) serving as controls. The circuit consisted of 10 stations performed on a Universal Gym, 3 circuits per day (approximately 22.5 min/day), 3 days/week. The subjects exercised at 40-55% of 1-RM, executing as many repetitions as possible in 30 sec on each of the lifts, followed by a 15 sec rest as the subject moved to the next station. Following the training program, the experimental groups demonstrated significant increases in lean body weight, flexed biceps girth, treadmill endurance time, VEmax (women only), Vo2max in ml/kg-min (women only), flexibility and strength. Significant decreases were found in selected skinfold measurements, and in resting heart rate (control group showed similar decreases). No change was found in body weight or in relative or absolute body fat. Generally, the women exhibited equal or greater changes when compared to the men for all variables assessed, which could be a function of their lower initial starting levels, or a more intense training program. It was concluded that circuit weight training is a good general conditioning activity, i.e., attends to more than one component of fitness.
Summary Dual-energy X-ray absorptiometry (DEXA) has been used to assess and compare the composition of whole body and major body regions in 12 female (weight, 56.9 ± 6–2 kg; BMI, 17.25 kg m-2) and 16 male (weight, 73.1 ± 9–6 kg; BMI, 20.28 kg m-2) healthy subjects. Standard deviations (and % coefficients of variation) of the differences between repeated measurements of fat ranged from 0.11 kg (9.0%) for arms to 0.42 kg (30%) for whole body; for arm bone mineral, 0.01 kg (2.0%), and for fat-free soft tissue of the whole body, 0.42 kg (0.8%). Limb muscle mass was estimated using a new theoretical model of body composition, and the corresponding precision ranged from 015 kg (3.8%) to 0.27 kg (1.5%) for arms and total limb muscle mass, respectively.
Proportions of each region consisting of fat were greater in females than in males (range, 20.31% vs. 16.18%), respectively, but the ratio of trunk to leg fat was lower (34:49% vs. 46:38%, respectively). Regional proportions of bone were similar between the sexes (all in the range 2.9–5.6%, for both females and males).
Mean total limb muscle masses were 14.2 kg (arms, 2.8 kg; legs, 11.4 kg) for females and 22.2 kg (arms, 4.8 kg; legs, 17.4 kg) for males, which were 33.6% and 36.0% of fat-free mass, respectively. The correlation coefficients between limb muscle (DEXA) and other indices of muscle mass were: for DEXA vs. total body potassium, 0.90 (SEE 1.1kg muscle mass) to 0.94 (1.6 kg); and for DEXA vs. anthropometry, 0.43 (1.2 kg) to 0.85 (1.3 kg). Those for limb volume (DEXA) vs. anthropometric volume, 0.91 (0.78 1) to 0.94 (1.91 1).
It is concluded that DEXA enables the valid and reproducible estimation of fat, fat-free soft tissue, bone, and limb muscle mass.
We have examined the effect of testosterone enanthate injections (3 mg/kg.week, im) on the basal metabolic rate (BMR) estimated by indirect calorimetry and on lean body mass (LBM) estimated by 40K counting in four normal men and nine men with muscular dystrophy. Testosterone treatment increased plasma testosterone levels in all subjects (3-fold mean elevation). BMR increased significantly after 3 months of testosterone treatment (mean, 10%; P less than 0.01; 13% mean increase in the men with muscular dystrophy and 7% mean increase in the normal subjects). BMR remained elevated (mean increase, 9%) after 12 months of testosterone treatment in four men with muscular dystrophy. LBM also was significantly higher after 3 months of treatment (mean, 10%; P less than 0.01) and remained elevated at 12 months. The percent increase in LBM was similar in men with muscular dystrophy (+10%) and normal men (+11%). When BMR was adjusted for the increase in LBM by linear regression, the men with muscular dystrophy had an increase in adjusted BMR after 3 months of testosterone treatment (mean increase, 7%), but not after 12 months. The normal men did not have an increase in adjusted BMR. Testosterone treatment for 12 months slightly reduced body fat, whereas there was an increase in body fat in subjects with muscular dystrophy who were treated with placebo for 12 months. We conclude that there is a significant increase in BMR associated with pharmacological testosterone treatment, which for the most part is explained by the increase in LBM. However, in men with muscular dystrophy, there is a small hypermetabolic effect of testosterone beyond that explained by increased LBM.
To assess whether alterations in the normal pattern of testosterone (T) secretion might be beneficial or detrimental, we studied a breeding population of dark-eyed juncos in which we elevated T experimentally and measured its effect on potential correlates of fitness. We treated both free-living and captive males with implants that were either empty (C-males, controls) or packed with T (T-males, experimentals). Timing of implant varied and was designed to mimic natural peak breeding levels except that peaks were either prolonged or premature. We bled the birds at recapture and analyzed their plasma, and that of their female mates, for T and corticosterone (B). We also measured body mass and fat score in free-living T- and C-males. In the field, T-implants elevated T and kept it elevated for at least a month. Experimental males also had higher B than controls. In captives, the effect of the implants on plasma T was detectable within 24 hr. B in captive T-males was again higher than in captive C-males. In females, neither T nor B differed between mates of T- and C-males. T-males implanted in early spring lost more mass between implant and recapture in late spring than did controls and also had lower fat scores when recaptured. When implants were inserted in summer, treatment did not influence mass. Elevated T in early spring apparently hastened the transition from the winter to the breeding mode of fat storage. We suggest that prolonged elevation of testosterone might be selected against because of the association between T and B. Premature elevation of T might be costly because of the resultant loss of mass and fat reserves, which could lead to mortality when spring snowstorms prevent access to food.
We have studied the effect of a pharmacological dose of testosterone enanthate (3 mg.kg-1.wk-1 for 12 wk) on muscle mass and total-body potassium and on whole-body and muscle protein synthesis in normal male subjects. Muscle mass estimated by creatinine excretion increased in all nine subjects (20% mean increase, P less than 0.02); total body potassium mass estimated by 40K counting increased in all subjects (12% mean increase, P less than 0.0001). In four subjects, a primed continuous infusion protocol with L-[1-13C]leucine was used to determine whole-body leucine flux and oxidation. Whole-body protein synthesis was estimated from nonoxidative flux. Muscle protein synthesis rate was determined by measuring [13C]leucine incorporation into muscle samples obtained by needle biopsy. Testosterone increased muscle protein synthesis in all subjects (27% mean increase, P less than 0.05). Leucine oxidation decreased slightly (17% mean decrease, P less than 0.01), but whole-body protein synthesis did not change significantly. Muscle morphometry showed no significant increase in muscle fiber diameter. These studies suggest that testosterone increases muscle mass by increasing muscle protein synthesis.
Sex hormones have been implicated in the pathogenesis of many autoimmune disorders, presumably through regulatory influences on the immune system. However, the mechanisms of sex steroid action on humoral and cellular immune responses are not precisely understood. In this study, the in vitro effects of physiologic concentrations of 17 beta-estradiol and testosterone on the Ag non-specific differentiation of human PBMC were examined using optimal and sub-optimal doses, respectively, of PWM. In cultures of PBMC from 14 normal donors (7 men and 7 women, aged 25 to 45 yr), 17 beta-estradiol (0.5 to 30 ng/ml) enhanced PWM-induced generation of PFC by 46% (p less than 0.01), whereas testosterone (10 to 300 ng/ml) inhibited PFC generation by a mean of 36% (p less than 0.001). The enhancing and suppressing effects of the sex steroids on PBMC occurred early inasmuch as estradiol and testosterone had to be added to the cultures at their initiation (6 and 24 h, respectively) in order to observe their influence. Moreover, deletion of the hormones from the cultures after as short a period as 12 h did not obviate their effects. There was no alteration of the kinetics of the response to PWM or an effect on the number of spontaneous PFC generated in vitro in the absence of PWM. In addition, there was no difference among men and women in response to either sex steroid, and within the female group, no variation was observed on different days of the menstrual cycle. These studies demonstrate direct immunoregulatory effects of specific sex steroids on human PBMC and support the idea that these hormones may have a role in the pathogenesis and treatment of some autoimmune disorders.
The immune system is regulated by the gonadal steroids estrogen, androgen, and progesterone, but the circulating levels of
these steroids can also be affected by immune system function. Such interactions appear to be mediated through the hypothalamic-pituitary-gonadal-thymic
axis and depend on pituitary luteinizing hormone released by thymic factors under the control of the gonadal steroids.
Immune reactivity is greater in females than in males. In both experimental animals and in man there is a greater preponderance of autoimmune diseases in females, compared with males. Studies in many experimental models have established that the underlying basis for this sex-related susceptibility is the marked effects of sex hormones. Sex hormones influence the onset and severity of immune-mediated pathologic conditions by modulating lymphocytes at all stages of life, prenatal, prepubertal, and postpubertal. However, despite extensive studies, the mechanisms of sex hormone action are not precisely understood. Earlier evidence suggested that the sex hormones acted via the thymus gland. In recent years it has become apparent that sex hormones can also influence the immune system by acting on several nonclassic target sites such as the immune system itself (nonthymic lymphoid organs), the central nervous system, the macrophage-macrocyte system, and the skeletal system. Immunoregulatory T cells appear to be most sensitive to sex hormone action among lymphoid cells. Several mechanisms of action of sex hormones are discussed in this review. The possibility of using sex hormone modulation of immune responses for the treatment of autoimmune disorders is a promising area for future investigation.