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Costs and benefits of fat-free muscle mass in men: Relationship to mating success, dietary requirements, and native immunity

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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.

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... 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 difference 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 difference 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 (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). ...
Chapter
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The dominant evolutionary theory of sexual attraction posits that attraction serves as a psychological mechanism for identifying healthy, fertile, and appropriate mates. According to this theory, humans and animals display cues that reflect their mate quality and are perceived as attractive by potential mates. There is evidence for such valid cues in human faces, bodies, and in 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 kinds of physical cues that men and women rely on in mate choice. We conclude by noting how central and evolutionarily important physical cues are even in contemporary sexual selection, and how the importance of physical cues of partner quality manifests in evolutionarily novel inventions such as physical self-enhancements, social media, and online dating.
... 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]. ...
Article
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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.
... The strategic shift in thresholds for signal detection experienced by neurotic individuals leads more often to protective false alarms which are essential in dangerous real-life situations, such as the COVID-19 pandemic. Viability selection and sexual selection (Cornwallis and Uller, 2010) might have acted together in selecting for higher threat vigilance in women (i.e., higher neuroticism) given women's relatively much lower strength and thus lower self-defense abilities (Lassek and Gaulin, 2009;Nettle, 2011). Although environments experienced by the sexes do not differ substantially, the impacts of undetected threats can be higher for women because of their lower strength and higher parental investment, which may partially increase selection pressures for women's higher neuroticism, anxiety, and risk aversion (Lassek and Gaulin, 2009;Nettle, 2011). ...
... Viability selection and sexual selection (Cornwallis and Uller, 2010) might have acted together in selecting for higher threat vigilance in women (i.e., higher neuroticism) given women's relatively much lower strength and thus lower self-defense abilities (Lassek and Gaulin, 2009;Nettle, 2011). Although environments experienced by the sexes do not differ substantially, the impacts of undetected threats can be higher for women because of their lower strength and higher parental investment, which may partially increase selection pressures for women's higher neuroticism, anxiety, and risk aversion (Lassek and Gaulin, 2009;Nettle, 2011). This evolutionary reason of more protective false alarms in women might also be behind women's higher levels of compliance with protective measures (Moran and Del Valle, 2016;Galasso et al., 2020) and behind female leaders' decision to act more quickly during the pandemic (Garikipati and Kambhampati, 2020; though see Aldrich and Lotito, 2020), potentially saving more lives. ...
Article
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The COVID-19 pandemic has caused a global societal, economic, and social upheaval unseen in living memory. There have been substantial cross-national differences in the kinds of policies implemented by political decision-makers to prevent the spread of the virus, to test the population, and to manage infected patients. Among other factors, these policies vary with politicians’ sex: early findings indicate that, on average, female leaders seem more focused on minimizing direct human suffering caused by the SARS-CoV-2 virus, while male leaders implement riskier short-term decisions, possibly aiming to minimize economic disruptions. These sex differences are consistent with broader findings in psychology, reflecting women’s stronger empathy, higher pathogen disgust, health concern, care-taking orientation, and dislike for the suffering of other people—as well as men’s higher risk-taking, Machiavellianism, psychopathy, narcissism, and focus on financial indicators of success and status. This review article contextualizes sex differences in pandemic leadership in an evolutionary framework. Evolution by natural selection is the only known process in nature that organizes organisms into higher degrees of functional order, or counteracts the unavoidable disorder that would otherwise ensue, and is therefore essential for explaining the origins of human sex differences. Differential sexual selection and parental investment between males and females, together with the sexual differentiation of the mammalian brain, drive sex differences in cognition and behavioral dispositions, underlying men’s and women’s leadership styles and decision-making during a global pandemic. According to the sexually dimorphic leadership specialization hypothesis, general psychobehavioral sex differences have been exapted during human evolution to create sexually dimorphic leadership styles. They may be facultatively co-opted by societies and/or followers when facing different kinds of ecological and/or sociopolitical threats, such as disease outbreaks or intergroup aggression. Early evidence indicates that against the invisible viral foe that can bring nations to their knees, the strategic circumspection of empathic feminine health “worriers” may bring more effective and humanitarian outcomes than the devil-may-care incaution of masculine risk-taking “warriors”.
... Both hypotheses predict any relationships should be absent among women, as their formidability is far lower than that of males (Lassek & Gaulin, 2009) and they have not been sexually selected for physical contest competition (Hill, Bailey, & Puts, 2017;Puts, 2010). Studies have generally shown support for both hypotheses using a variety of measures of formidability and egalitarianism. ...
... Both height and muscularity are thought to be key components of formidability (Blaker & van Vugt, 2014), and were both intrasexually selected to be higher in males throughout our evolutionary history (Hill et al., 2017;Puts, 2010). However upper body strength is far more sexually dimorphic than height is, with some studies estimating that male strength is on average around 3 standard deviations higher than women's (Lassek & Gaulin, 2009). In the present study, the average male height was 1.75 SD above the average female height. ...
Article
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People vary widely in their attitudes towards how much their government should redistribute wealth. Evolutionary theory may shed light on why this variation occurs. Numerous studies have established an association between upper body strength and attitudes towards equality and wealth redistribution in males, showing that physically stronger men are more likely to hold self-serving beliefs on these issues. This effect is typically weaker or absent in women. A question that has received little attention is whether there are similar associations between other aspects of formidability and attitudes towards wealth redistribution. One such aspect is height. I tested this prediction using data from the European Social Survey, in a sample of 27031 people from 20 European countries. Results show that taller people are more likely to have self-serving attitudes towards government redistribution of wealth. The result was robust to numerous control variables and alternative model specifications, but the direct effects of height were small. Taller individuals were less supportive of government wealth redistribution overall, but were especially averse if they were also wealthier. Post-hoc analyses suggested that for lower income deciles, the association was reversed. For these people, there was a positive association between height and support for wealth redistribution. However, effects were equally strong in males and females, and so are not fully consistent with current evolutionary psychological theories of resource distribution.
... Moreover, some work has hinted at a link between body morphology and the perception of threat and guilt [26,27]. Here, biases often emerge against larger people. ...
... Until we understand the link between body morphology and trait perception, it remains difficult to test and prescribe methods to alleviate the effects of potential biases. Perceived threat is a particularly vital inference yet to be explored [25], not only due to its evolutionary importance [26], but also due to its capacity to potentially promote biases and to alter social outcomes, such as leadership contests and criminal sentencing. Experimental studies on the effects of body morphology have been primarily restricted to work still using faces as the presented stimuli [28,30], or more abstract, unrealistic body stimuli [33,34]. ...
Article
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People make judgments of others based on appearance, and these inferences can affect social interactions. Although the importance of facial appearance in these judgments is well established, the impact of the body morphology remains unclear. Specifically, it is unknown whether experimentally varied body morphology has an impact on perception of threat in others. In two preregistered experiments ( N = 250), participants made judgments of perceived threat of body stimuli of varying morphology, both in the absence (Experiment 1) and presence (Experiment 2) of facial information. Bodies were perceived as more threatening as they increased in mass with added musculature and portliness, and less threatening as they increased in emaciation. The impact of musculature endured even in the presence of faces, although faces contributed more to the overall threat judgment. The relative contributions of the faces and bodies seemed to be driven by discordance, such that threatening faces exerted the most influence when paired with non-threatening bodies, and vice versa. This suggests that the faces and bodies were not perceived as entirely independent and separate components. Overall, these findings suggest that body morphology plays an important role in perceived threat and may bias real-world judgments.
... 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). ...
Article
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.
... HGS (hand-grip strength) is a marker of masculinization reflecting overall body strength [43]. HGS in males significantly increases at puberty and becomes highly sexually dimorphic [44,45]. The largest increase in HGS is observed between 10-20 years old, with this remaining stable for up to 40-50 years [46]. ...
... Multiple regression models for adaptive immunity parameters and masculinity markers. linking SHR with any of the immune-associated biomarkers, and there have only been limited studies testing the relationship between muscle mass and immunity [45], with only one study directly testing CD4+ count and muscle functions itself as measured by strength [65]. This was, however, only in patients with an HIV-associated immune injury. ...
Article
Full-text available
Masculinity-related morphological traits are supposed to be honest indicators of a man's biological quality. While some studies showed that sexually dimorphic traits are related to various aspects of biological condition such as general health, immunity or fertility, still little is known about the relationship between masculine traits and the effectiveness of innate and adaptive immunity in humans. The aim of this study was to see if masculine traits, which are dependent on androgen levels in foetal and pubertal stages of development, are related to the immune quality in healthy men. The immune quality was evaluated for 91 healthy men aged 19–36 years. Immunity measurements included innate and adaptive parameters. General health status, age, testosterone level, BMI, physical activity, and smoking were controlled. The shoulder-to-hip ratio (SHR), 2D:4D digit ratio and hand-grip strength (HGS) were used as markers of masculinization. The regressions showed that when controlling for confounds, masculinity-related traits were in general not related to innate and adaptive immunity. Only a weak association was observed for right 2D:4D ratio and T-lymphocyte counts (but it becomes non-significant after adjustment for multiple comparisons). Our results do not support the premise that masculinity is a cue for immunological quality in men. However, the positive association between right 2D:4D and T lymphocytes might suggest that further studies are needed to verify if androgen stimulation in prenatal development might be related to immunity in adulthood.
... 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). ...
Article
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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.
... The strategic shift in thresholds for signal detection experienced by neurotic individuals leads more often to protective false alarms which are essential in dangerous real-life situations, such as the COVID-19 pandemic. Viability selection and sexual selection (Cornwallis and Uller, 2010) might have acted together in selecting for higher threat vigilance in women (i.e., higher neuroticism) given women's relatively much lower strength and thus lower self-defense abilities (Lassek and Gaulin, 2009;Nettle, 2011). Although environments experienced by the sexes do not differ substantially, the impacts of undetected threats can be higher for women because of their lower strength and higher parental investment, which may partially increase selection pressures for women's higher neuroticism, anxiety, and risk aversion (Lassek and Gaulin, 2009;Nettle, 2011). ...
... Viability selection and sexual selection (Cornwallis and Uller, 2010) might have acted together in selecting for higher threat vigilance in women (i.e., higher neuroticism) given women's relatively much lower strength and thus lower self-defense abilities (Lassek and Gaulin, 2009;Nettle, 2011). Although environments experienced by the sexes do not differ substantially, the impacts of undetected threats can be higher for women because of their lower strength and higher parental investment, which may partially increase selection pressures for women's higher neuroticism, anxiety, and risk aversion (Lassek and Gaulin, 2009;Nettle, 2011). This evolutionary reason of more protective false alarms in women might also be behind women's higher levels of compliance with protective measures (Moran and Del Valle, 2016;Galasso et al., 2020) and behind female leaders' decision to act more quickly during the pandemic (Garikipati and Kambhampati, 2020; though see Aldrich and Lotito, 2020), potentially saving more lives. ...
Preprint
Full-text available
The COVID-19 pandemic has caused a global societal, economic, and social upheaval unseen in living memory. There have been substantial differences in the kinds of policies implemented by political decision-makers to prevent the spread of the virus, to test the population, and to manage infected patients. Among other factors, these policies vary with politicians’ sex: early findings indicate that, on average, female leaders seem more focused on minimizing direct human suffering caused by the SARS-CoV-2 virus, while male leaders implement riskier short-term decisions, possibly aiming to minimize economic disruptions. These sex differences are consistent with broader findings in psychology, reflecting women’s stronger empathy, higher pathogen disgust, health concern, care-taking orientation, and dislike for the suffering of other people—as well as men’s higher risk-taking, Machiavellianism, psychopathy, narcissism, and focus on financial indicators of success and status. This review article contextualizes sex differences in pandemic leadership in an evolutionary framework. Evolution by natural selection is the only known process in nature that organizes organisms into higher degrees of functional order, or counteracts the unavoidable disorder that would otherwise ensue, and is therefore essential for explaining the origins of human sex differences. Differential sexual selection and parental investment between males and females, together with the sexual differentiation of the mammalian brain, drive sex differences in cognition and behavioral dispositions, underlying men’s and women’s leadership styles and decision-making during a global pandemic. According to the sexually dimorphic leadership specialization hypothesis, general psychobehavioral sex differences have been exapted during human evolution to create sexually dimorphic leadership styles. They may be facultatively co-opted by societies and/or followers when facing different kinds of ecological and/or sociopolitical threats, such as disease outbreaks or intergroup aggression. Early evidence indicates that against the invisible viral foe that can bring nations to their knees, the strategic circumspection of empathic feminine health “worriers” may bring more effective and humanitarian outcomes than the devil-may-care incaution of masculine risk-taking “warriors”.
... 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. ...
Article
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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.
... When selecting those most effective for intergroup conflict, formidability becomes highly valuated. Through sexual selection pressures to outcompete other men intrasexually for access to high quality mates, sexual dimorphism emerged over time, with men being larger and more muscular than women (Lassek & Gaulin, 2009). Consequently, this formidability became one basis of men's social value beyond reproductive contexts, particularly in protective domains. ...
... The coevolution of physical conflict with the sexual dimorphism in formidability has led to conflict becoming sexually asymmetric, with men engaging more frequently in physical confrontation (Sell et al., 2012). Although the concomitant size asymmetry imposed by human sexual dimorphism is not as large as it is for other primates (Plavcan, 2012), human males nonetheless possess greater muscle mass and cranial robusticity compared to women in addition to a heightened proclivity to engage in physical aggression and weapon use (Hill, Bailey, & Puts, 2017;Lassek & Gaulin, 2009). Formidable men possess an adaptive advantage in intrasexual competition that would subsequently connote their heritable fitness to prospective mates, making formidability sexually selected (Puts, 2010), though adaptively beneficial beyond direct reproduction as well, such as in facilitating coalitional exploitation. ...
Article
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. Women high in social dominance orientation built more formidable coalitions in resource-abundant ecologies. Men's coalitional interests were unaffected by these factors. We frame results through evolved sex differences in coalition-building based on men and women's different formidability valuation thresholds while considering ancestral logic behind political ideology related to resource acquisition.
... Continuing the enumeration from above, fifth, archeological evidence suggests that males have been physically larger than females in all human hominid groups dating back three to four million years (Geary, 1998). This translates in current times to men having on average 61 percent more muscle mass (Lassek and Gaulin, 2009) and roughly 50 to 100 percent more upper-body strength than women (Pheasant, 1983), with female and male distributions in upper-body strength and muscle mass overlapping by less than 10 percent (Lassek and Gaulin, 2009). This sexual dimorphism suggests that when physical formidability is a desirable trait, males are greatly advantaged over females. ...
... Continuing the enumeration from above, fifth, archeological evidence suggests that males have been physically larger than females in all human hominid groups dating back three to four million years (Geary, 1998). This translates in current times to men having on average 61 percent more muscle mass (Lassek and Gaulin, 2009) and roughly 50 to 100 percent more upper-body strength than women (Pheasant, 1983), with female and male distributions in upper-body strength and muscle mass overlapping by less than 10 percent (Lassek and Gaulin, 2009). This sexual dimorphism suggests that when physical formidability is a desirable trait, males are greatly advantaged over females. ...
Article
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Females constitute a far smaller proportion of political leaders than their proportion in the general population. Leading demand- and supply side explanations for this phenomenon account for some of the variance but leave a great deal unexplained. In an effort to account for additional variance, this research evaluates the issue informed by the biological theory of evolution by natural selection, a foundational explanation for the diversity and function of living organisms. It experimentally assesses how varying types of inter- and intragroup threat–a recurring ancestral problem–affect demand for female and male national leaders. This work analyzes data collected from individuals (N = 826) in the U.S. during the 2012 Cooperative Congressional Election Study. The results suggest the predominant preference for male over female leaders in some contexts may be the non-adaptive and non-functional but lingering outcome of an adaptive preference for physically formidable allies that was shaped by natural selection in ancestral environments.
... Humans are characterised by a strong sexual dimorphism in physical dominance, or the ability to inflict damage on others (see Lassek & Gaulin, 2009). Physical dominance, sometimes called formidability in the psychological literature, is mostly determined by being tall and muscular (Blaker & Van Vugt, 2014). ...
... Strong, muscular men are more attractive to women (Durkee et al., 2019;Frederick & Haselton, 2007;Sell, Lukazsweski, & Townsley, 2017) as are men with status and resources (Buss, 1989). Men with more masculine, dominant faces, bodies and voices also report greater mating success (Apicella, Feinberg, & Marlowe, 2007;Hill et al., 2013;Kordsmeyer, Hunt, Puts, Ostner, & Penke, 2018;Lassek & Gaulin, 2009;Puts, 2005;Rhodes, Simmons, & Peters, 2005). ...
Article
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There is considerable evidence that human male faces contain honest, detectable cues to their physical dominance, which are related to their objective facial masculinity. As such, some have argued that the extent to which observers' rate masculinised male faces as appearing more physically dominant is a useful measure of their ability to detect cues of dominance and threat in other men. We found across 3 studies (total n = 272) that younger, taller, and stronger men showed greater sensitivity to facial cues of dominance. Additionally, participants were more likely to associate younger than older masculinised faces with physical dominance. Self-perceived social dominance did not moderate perceptions. These results contrast with previous work which found that shorter, less socially dominant men had greater ability to detect facial cues of dominance. We propose the hypothesis that younger, more formidable males show greater sensitivity to facial cues of dominance as they are more likely to engage in violent intrasexual competition.
... Although the level of dimorphism between women and men is relatively small compared to other primate species, on average men are roughly 25 percent heavier and 7 percent taller than women (Archer, 2009;Gustafsson & Lindenfors, 2004). Additionally, men have about 61 percent greater muscle mass than women (Lassek & Gaulin, 2009). Bodily dimorphism strongly predicts degree of conspicuous inter-male competitive behavior across primates (Plavcan & van Schaik, 1997). ...
... Therefore, it is likely adaptive for women to show greater concern with their general health, to avoid risk, and to elude direct physical confrontation whenever possible. This is reflected in women's use of "low-risk" antagonistic strategies, indicative of indirect aggression, as well as their less pronounced sexually selected traits that are associated with direct intrasexual combat in men, such as musculature, height, and weight (Lassek & Gaulin, 2009), and traits associated with male aggressive displays, such as beards (e.g., Muscarella & Cunningham, 1996), voice pitch (e.g., Sell et al., 2010), and facial robustness (e.g., Toscano, Schubert, & Sell, 2014). ...
Chapter
From an evolutionary perspective, aggression is viewed as a flexible context-specific adaption that was selected for because it enhanced the survival and reproductive success of ancestral humans. Evolutionary pressures have impinged differentially on the sexes, leading to the hypothesis that sex differences should be manifest in aggressive behavior. Evidence to date supports key predictions made from sexual selection theory that women direct their aggression primarily toward same-sex competitors, which peaks as mate competition intensifies. Women demonstrate a notable preference across cultures for more indirect, as opposed to direct, forms of intrasexual rivalry as a likely consequence of heightened obligatory parental investment, lower lifetime reproductive potential, and the greater importance of maternal survival for the health and longevity of offspring. An evolutionary approach can yield unique insights into the sex-differentiated functions, development, and outcomes of aggressive behavior.
... For example, perhaps the most dubious assumption underlies hypotheses #4: Is the world really more dangerous for women than men when men are more likely to be killed violently and die on average five years sooner (e.g., Rochelle, Yeung, Bond, & Li, 2015)? Perhaps, but among a variety of threats that disproportionately impact women, it is indisputable that most women spend life surrounded by biologically stronger, faster, more aggressive individuals who are motivated to assault them, often do, and whose denials are traditionally more likely to be believed over women's accusations (e.g., Lassek & Gaulin, 2009). Thus, if researchers were to find that nevertheless women and men see the world as equally Safe, that can be considered inconsistent with a retrospective theory of how Safe develops, though not compelling unless other hypotheses relying on different assumptions are also examined. ...
Article
If behavior is influenced by the perceived character of situations, many disciplines that study behavior may eventually need to take into account individual differences in the perceived character of the world. In the first effort to empirically map these perceptions, subjects varied on 26 dimensions, called primal world beliefs or primals, such as the belief that the world is abundant. This dissertation leverages the first comprehensive measure of primals to further discussions in political, developmental, clinical, and positive psychology. Chapter I challenges the consensus that political conservativism is distinguished by the belief that the world is dangerous. Results suggest previous research relied on a measure highlighting dangers conservatives fear and neglecting dangers liberals fear, when both perceive the world as almost equally dangerous (8 samples; total N=3,734). A novel account of political ideology is proposed based on more predictive primals. Chapter II discusses how primals might develop. The author distinguishes retrospective theories—where primals reflect the content of past experiences—from interpretive theories—where primals act as lenses for interpreting experiences while remaining uninfluenced by them—and suggests twelve ways each theory’s relative merit can be empirically tested. A novel comprehensive framework for considering experiences in relation to any new construct is also proposed. Chapter III explores primals’ wellbeing-related correlates. By showing that many parents aim to teach negative primals to their children, some prevalence for meta-beliefs (i.e., beliefs about beliefs) associating negative primals with positive outcomes is established. Study 2 tests these meta-beliefs in six samples (total N=4,535) in regards to eight outcomes: job success, job satisfaction, emotion, depression, suicide, physical health, life satisfaction, and flourishing. Results indicate that negative primals are almost always associated with modestly to dramatically worse outcomes, across and within professions. In addition to filling a literature gap, and establishing bases for future comparison studies, findings could be used to strengthen interventions by undermining counterproductive meta-beliefs. Findings also underscore the urgent need for further research on the impact of primal world beliefs—teaching children or anyone that the world is a bad place in order to protect or prepare them may be ill-advised.
... Our study was limited in that we only evaluated men's ratings of and recognition memory for masculinized and feminized men's faces; however, in future investigations we intend to collect data from both sexes. The sex differences in strength make women more vulnerable to aggression and thus suggest greater female sensitivity to threat (e.g., Geniole & McCormick, 2013;Lassek & Gaulin, 2009). Future studies should aim to test women's ability to assess physical dominance from masculinized and feminized men's faces while controlling for the affects that masculinized and feminizing these faces has on women's attractiveness perceptions. ...
Article
Research has consistently demonstrated that faces manipulated to appear more masculine are perceived as more dominant. These studies, however, have used forced-choice paradigms, in which a pair of masculinized and feminized faces was presented side by side. These studies are susceptible to demand characteristics, because participants may be able to draw the conclusion that faces which appear more masculine should be rated as more dominant. To prevent this, we tested if dominance could be perceived when masculinized or feminized faces were presented individually for only 100 ms. We predicted higher dominance ratings to masculinized faces and better memory of them in a surprise recognition memory test. In the experiment, 96 men rated the physical dominance of 40 facial photographs (masculinized = 20, feminized = 20), which were randomly drawn from a larger set of faces. This was followed by a surprise recognition memory test. Half of the participants were assigned to a condition in which the contours of the facial photographs were set to an oval to control for sexual dimorphism in face shape. Overall, men assigned higher dominance ratings to masculinized faces, suggesting that they can appraise differences in facial sexual dimorphism following very brief exposure. This effect occurred regardless of whether the outline of the face was set to an oval, suggesting that masculinized internal facial features were sufficient to affect dominance ratings. However, participants' recognition memory did not differ for masculinized and feminized faces, which could be due to a floor effect. K E Y W O R D S aggression, dominance, intrasexual competition, sexual dimorphism
... The increasing performance gap between males and females as upper body strength becomes more critical for performance is likely explained to a large extent by the observation that males have disproportionately greater strength in their upper compared to lower body, while females show the inverse [44,45]. This different distribution of strength compounds the general advantage of increased muscle mass in upper body dominant disciplines. ...
Article
Full-text available
Males enjoy physical performance advantages over females within competitive sport. The sex-based segregation into male and female sporting categories does not account for transgender persons who experience incongruence between their biological sex and their experienced gender identity. Accordingly, the International Olympic Committee (IOC) determined criteria by which a transgender woman may be eligible to compete in the female category, requiring total serum testosterone levels to be suppressed below 10 nmol/L for at least 12 months prior to and during competition. Whether this regulation removes the male performance advantage has not been scrutinized. Here, we review how differences in biological characteristics between biological males and females affect sporting performance and assess whether evidence exists to support the assumption that testosterone suppression in transgender women removes the male performance advantage and thus delivers fair and safe competition. We report that the performance gap between males and females becomes significant at puberty and often amounts to 10–50% depending on sport. The performance gap is more pronounced in sporting activities relying on muscle mass and explosive strength, particularly in the upper body. Longitudinal studies examining the effects of testosterone suppression on muscle mass and strength in transgender women consistently show very modest changes, where the loss of lean body mass, muscle area and strength typically amounts to approximately 5% after 12 months of treatment. Thus, the muscular advantage enjoyed by transgender women is only minimally reduced when testosterone is suppressed. Sports organizations should consider this evidence when reassessing current policies regarding participation of transgender women in the female category of sport.
... Tā kā testosterons veicina imūno funkciju un palielināta muskuļu masa ir saistīta ar augstas enerģijas pieejamību, muskuļi signalizē par labu veselību un imūnsistēmu, turklāt spēja veidot lielāku muskuļu masu ir daļēji pārmantojama, kas liecina, ka priekšrocības, kas saistītas ar muskulatūru, var tikt nodotas pēcnācējiem [22,[11][12][13]. Attiecībā uz muskuļu masu starp dzimumiem ir būtiska atšķirība [43,324], kas liecina par to, ka priekšteču vīriešiem muskuļu masa ir sniegusi priekšrocības medībās, resursu iegūšanā un vīriešu savstarpējā konkurencē [52,169]. Ir zināms, ka daudzi vīrieši vēlas kļūt muskuļotāki, lai būtu pievilcīgāki sievietēm un veiksmīgāki sacensībās ar citiem vīriešiem [22,113]. ...
Article
Full-text available
Cilvēka vizuālais tēls iemanto apjomīgu sociāli bioloģiskās informācijas daudzumu. Tas norāda uz dzimumu, vecumu, rasi, veselības stāvokli, auglību, hormonu līmeni un pat uz paredzamo uzvedību un dzīves ilgumu. Tā ir būtiska privātā informācija, kas ikdienā nav aizsargāta un kas ir eksponēta apkārtējiem. Latvijā katrs trešais skolēns saskaras ar mobingu, un tas ir viens no augstākajiem rādītājiem starp Ekonomiskās sadarbības un attīstības organizācijas valstīm. Piemēram, visticamāk, tieši mobings bijis par iemeslu 16 gadu veca puiša pašnāvībai, kas notika 2019. gadā. Zināms, ka pašnāvība ir sociālās atstumtības rezultāts, un Latvijā ir trešais lielākais pašnāvību izdarījušo cilvēku skaits Eiropas Savienībā. Rakstā tiek analizēta vizuālā tēla sociāli bioloģiskā koncepcija, sniegti argumenti tā aizsardzībai un nozīmīgumam sabiedrībā kopsakarā ar spēkā esošajām tiesību normām un judikatūru. Nobeigumā ir priekšlikums, kas attiecināms uz likumprojektu “Sejas aizsegšanas ierobežojuma likums”, kā arī uz sejas atpazīšanas videonovērošanas sistēmas iespējamu ieviešanu. Visual image of a man is a considerable amount of socially biological information. This includes gender, age, race, health, fertility, hormone levels, even behavior, and life expectancy. It is essentially private information that is not protected day-to-day basis and is rather exposed to the surrounding individuals. In Latvia, every third pupil faces bullying, which is one of the highest rates among OECD countries. For example, in 2019, it was more likely that bullying had been the reason for suicide of a 16-year-old boy. It is known that suicide is the result of social exclusion, and Latvia possesses the third largest number of people who have committed suicide in the European Union. The article analyses socio-biological concept of visual image, arguments for its protection and its importance in society, compliance with existing legal provisions and case law. A proposal has been made for the establishment of legal provisions relating to the draft of the Facial Masking Limitation Law, as well as for the possible introduction of a facial recognition video surveillance system.
... Visible body size and musculature, which are reflective of strength and dominance, are associated with a high energy cost for the whole body. 49,50,51 Apart from such visual stimuli, auditory stimuli are also evocative of male physical dominance. Drawing on the trade-offs principle, it is more advantageous to evoke such stimuli without necessarily enhancing body size 52 which in turn, may lead to the voice masking putative body size. ...
Article
Objectives: From a human evolution perspective, identifying a link between physique and vocal quality could demonstrate dual signaling in terms of the health and biological condition of an individual. In this regard, this study investigates the relationship between men's body size, shape, and composition, and their vocal characteristics. Materials and methods: Eleven anthropometric measurements, using seven indices, were carried out with 80 adult Polish male participants, while the speech analysis adopted a voice recording procedure that involved phonetically recording vowels /ɑː/, /ɛː/, /iː/, /ɔː/, /uː/ to define the voice acoustic components used in Praat software. Results: The relationship between voice parameters and body size/shape/composition was found. The analysis indicated that the formants and their derivatives were useful parameters for prediction of height, weight, neck, shoulder, waist, and hip circumferences. Fundamental frequency (F0) was negatively correlated with neck circumference at Adam's apple level and body height. Moreover neck circumference and F0 association was observed for the first time in this paper. The association between waist circumference and formant component showed a net effect. In addition, the formant parameters showed significant correlations with body shape, indicating a lower vocal timbre in men with a larger relative waist circumference. Discussion: Men with lower vocal pitch had wider necks, probably a result of larynx size. Furthermore, a greater waist circumference, presumably resulting from abdominal fat distribution in men, correlated with a lower vocal timbre. While these results are inconclusive, they highlight new directions for further research.
... For example, in polygynous kangaroo species, male-biased dimorphism is found in forearm length and forelimb muscle mass that function to improve performance in grappling and striking 952 JOURNAL OF MAMMALOGY actions that occur during fights (Jarman 1983(Jarman , 1989Warburton et al. 2013). Similar patterns of male-biased dimorphism in forelimb morphology are found in other species that strike with their forelimbs when fighting, including western lowland gorillas (Gorilla gorilla- Zihlman and McFarland 2000) and humans (Lassek and Gaulin 2009). In carnivores and primates, male-biased sexual dimorphism is found in a variety of skeletal shape traits that increase muscle attachment area, anatomical mechanical advantages, and safety factors in limb bones (Morris and Brandt 2014;Morris and Carrier 2016;Morris et al. 2019). ...
Article
Sexual dimorphism evolves as a response to different selective pressures on males and females. In mammals, sexual selection on traits that improve a male’s ability to compete for access to mates is a common cause of sexual dimorphism. In addition to body mass, adaptations in specific components of the musculoskeletal system that increase strength, stability, and agility, may improve male fighting performance. Here we test the hypotheses that males, when compared to females, are more specialized for physical competition in their skeletal anatomy and that the degree of this sexual dimorphism increases with the intensity of male–male competition. In three species of voles (Cricetidae: Arvicolinae: Microtus), we found partial support for these hypotheses. Male-biased sexual dimorphism in a set of functional indices associated with improved fighting performance was identified in the postcranial anatomy. This dimorphism was greatest in the polygynous Microtus californicus, absent in the monogamous M. ochrogaster, and intermediate in the promiscuous or socially flexible M. oeconomus. However, in the skull, we found results opposite to our predictions. Females had larger skulls relative to overall skeletal size than did males. This may be associated with selection for increased food processing efficiency, which should be highly important because of the compounding effects of increased caloric requirements during gestation and lactation, and the generally low-quality diet of voles. In addition, larger heads in females may be associated with selection for greater digging ability or for defending offspring. These results suggest disparate selective pressures on the postcranial skeletons and skulls of male and female voles.
... Monomorphic canines are usually found in primates where males and females are approximately the same size and live in small groups, with male and female roles overlapping extensively and males often providing care for the young. The overall size difference between human men and women in modern samples is around 10% to 20% (Lassek and Gaulin 2009;McHenry and Coffing 2000;Plavcan 2000;Plavcan and van Schaik 1997), considerably smaller than gorillas (63%) and a little smaller than the typical primate (around 25%; Lindenfors and Tullberg 2011). Dimorphism in humans is on the lower end of that in the chimpanzee (20% to 30%), and our canines are monomorphic, unlike the majority of bodysize dimorphic primate species. ...
Article
The reconstruction and prioritization of masculinity in human evolution (and thus human nature) is often rooted in reference to other primates and the hominin fossil and archaeological record. And it almost always involves violence. Whether it be the “demonic males” hypothesis, the trope of aggressive alpha maleness and sexual coercion, or gender-biased representations of toolmaking, hunting, and fierce encounters between different populations of the genus Homo in the Pleistocene, a particular pattern of masculinity (maleness)—and violence—permeates most popular discourse and much of the academic discourse. While there are some significant sexual differences and divergent strategies among our closest cousins, and the fossil record does offer important insights into the development and deployment of gender, much of the data do not fit seamlessly with typical assumptions. In fact, much in our contemporary understandings of other primate behavior and the hominins either contradicts or complexifies assumptions and assertions about the origins and “ancestral” patterns of contemporary human masculinity and its associated violence. This paper articulates what we do and do not know about maleness in primates and past humans and offers some possibilities for how such information might assist in elaborating more integrative understandings of the complexities of human masculinities. © 2020 by The Wenner-Gren Foundation for Anthropological Research. All rights reserved.
... 6 The gender-related differences in strength may be attributed to the women's tendency to have lower lean body mass, 25 and the upper-body muscularity of men. 26 According to Isen et al.,27 this gender dimorphism in physical strength between men and women overcomes the differences between the genders in terms of overall body mass and height, and thus likely reflects the higher levels of androgenic hormones. 28 These hormones promote an intense physiological effect on body composition (indeed, testosterone is considered a physiological marker of the body's anabolic state and of muscle strength). ...
Article
Full-text available
Objective The present study aimed to investigate the physical performance of handgrip strength (HGS) in women with polycystic ovary syndrome (PCOS). Methods A case-control study that included 70 women with PCOS and 93 age-matched healthy women aged between 18 and 47 years with body mass index (BMI) between 18 Kg/m2–39.9 Kg/m2. The serum levels of total testosterone, androstenedione, insulin, estradiol, thyroid-stimulating hormone (TSH), prolactin, sex hormone-binding globulin (SHBG), and 17-hydroxyprogesterone (17-OHP) were measured. The free androgen index (FAI) and the homeostatic model assessment of insulin resistance (HOMA-IR) were calculated. The body composition regions of interest (ROIs) were assessed by dual-energy X-ray absorptiometry (DXA), and the handgrip strength (HGS) was evaluated for both the dominant and the non-dominant hands with a manual Sammons Preston (Bolingbrook, IL, US) bulb dynamometer. Results Women with PCOS had high serum levels of total testosterone (p < 0.01), androstenedione (p = 0.03), and insulin (p < 0.01), as well as high FAI (p < 0.01) and HOMA-IR (p = 0.01) scores. Compared with the non-PCOS group, the PCOS group had greater total lean mass in the dominant hand (p < 0.03) and greater HGS in both the dominant and the non-dominant hands (p < 0.01). The HGS was correlated with lean mass (p < 0.01). Conclusion Women with PCOS have greater HGS. This may be associated with age and BMI, and it may be related to lean mass. In addition, the dominance effect on muscle mass may influence the physical performance regarding HGS in women with PCOS.
... Sexual dimorphism and/or sex differences occur in various traits and life history strategies that comprise important components of fitness 10,[19][20][21][22] . Phenotypic characteristics such as body size 5,23-25 , physical strength 26,27 , appearance 28 and immune defense 3,6,29 all show significant sex differences in humans. These differences are influenced by genetics 21,30,31 , but also by socioeconomic and environmental factors 15,32,33 . ...
Article
Full-text available
Immune function, height and resource accumulation comprise important life history traits in humans. Resource availability models arising from life history theory suggest that socioeconomic conditions influence immune function, growth and health status. In this study, we tested whether there are associations between family income during ontogeny, adult height, cortisol level and immune response in women. A hepatitis B vaccine was administered to 66 young Latvian women from different socioeconomic backgrounds, and blood samples were then collected to measure the level of antibodies that the women produced in response to the vaccination. Cortisol levels were measured from plasma samples pre- and post-vaccination. Women from wealthier families had lower cortisol levels, and women from the highest family income group had the highest levels of antibody titers against hepatitis B vaccine. No significant relationships were observed between cortisol level and immune function, nor between family income and height. The results show that income level during ontogeny is associated with the strength of immune response and with psychoneuroendocrine pathways underlying stress perception in early adulthood. The findings indicate that the quality of the developmental niche is associated with the condition-dependent expression of immune function and stress response.
... Implicitly, individuals associate men with threat, violence, destruction, and anger-associations congruent with the perpetrator role (Rudman & Goodwin, 2004;Rudman et al., 2001). Men's morphology may strengthen these associations as their bodies have higher proportions of lean muscle mass on average than do women's (Lassek & Gaulin, 2009). People perceive muscular, compared to leaner, individuals as less vulnerable, experience less pity in response to their suffering, and are less motivated to protect them (Dijker, 2001). ...
Article
Full-text available
Informed by moral typecasting theory, we predicted a gender bias in harm evaluation, such that women are more easily categorized as victims and men as perpetrators. Study 1 participants assumed a harmed target was female (versus male), but especially when labeled ‘victim’. Study 2 participants perceived animated shapes perpetuating harm as male and victimized shapes as female. Study 3 participants assumed a female employee claiming harassment was more of a victim than a male employee making identical claims. Female victims were expected to experience more pain from an ambiguous joke and male perpetrators were prescribed harsher punishments (Study 4). Managers were perceived as less moral when firing female (versus male) employees (Study 5). The possibility of gender discrimination intensified the cognitive link between women and victimhood (Study 6). Across six studies in four countries (N = 3,137), harm evaluations were systematically swayed by targets’ gender, suggesting a gender bias in moral typecasting.
... For example, perhaps the most dubious assumption underlies hypotheses #4: Is the world really more dangerous for women than men when men are more likely to be killed violently and die on average 5 years sooner (e.g., Rochelle et al., 2015)? Perhaps, but among a variety of threats that disproportionately impact women, it is indisputable that most women spend life surrounded by biologically stronger, faster, more aggressive individuals who are motivated to assault them, often do, and whose denials are traditionally more likely to be believed over women's accusations (e.g., Lassek and Gaulin, 2009). Thus, if researchers were to find that nevertheless women and men see the world as equally Safe, that can be considered inconsistent with a retrospective theory of how Safe develops, though not compelling unless other hypotheses relying on different assumptions are also examined. ...
Article
Full-text available
Do negative primal world beliefs reflect experiences such as trauma, crime, or low socio-economic status? Clifton and colleagues recently suggested that primals—defined as beliefs about the general character of the world as a whole, such as the belief that the world is safe (vs. dangerous) and abundant (vs. barren)—may shape many of the most-studied variables in psychology. Yet researchers do not yet know why individuals adopt their primals nor the role of experience in shaping primals. Many theories can be called retrospective theories; these theories suggest that past experiences lead to the adoption of primals that reflect those experiences. For example, trauma increases the belief that the world is dangerous and growing up poor increases the belief that the world is barren. Alternatively, interpretive theories hold that primals function primarily as lenses on experiences while being themselves largely unaffected by them. This article identifies twelve empirical tests where each theory makes different predictions and hypothesizes that retrospective theories are typically less accurate than interpretive theories. I end noting that, even if retrospective theories are typically inaccurate, that does not imply experiences do not shape primals. I end by offering a conceptual architecture—the Cube Framework—for exploring the full range of human experience and suggest that, though psychologists have historically focused on negative, externally imposed experiences of short-duration (e.g., trauma), positive, internally driven, and longer-term experiences are also worth considering.
... For example, perhaps the most dubious assumption underlies hypotheses #4: Is the world really more dangerous for women than men when men are more likely to be killed violently and die on average five years sooner (e.g., Rochelle, Yeung, Bond, & Li, 2015)? Perhaps, but among a variety of threats that disproportionately impact women, it is indisputable that most women spend life surrounded by biologically stronger, faster, more aggressive individuals who are motivated to assault them, often do, and whose denials are traditionally more likely to be believed over women's accusations (e.g., Lassek & Gaulin, 2009). Thus, if researchers were to find that nevertheless women and men see the world as equally Safe, that can be considered inconsistent with a retrospective theory of how Safe develops, though not compelling unless other hypotheses relying on different assumptions are also examined. ...
Thesis
Full-text available
If behavior is influenced by the perceived character of situations, many disciplines that study behavior may eventually need to take into account individual differences in the perceived character of the world. In the first effort to empirically map these perceptions, subjects varied on 26 dimensions, called primal world beliefs or primals, such as the belief that the world is abundant. This dissertation leverages the first comprehensive measure of primals to further discussions in political, developmental, clinical, and positive psychology. Chapter I challenges the consensus that political conservativism is distinguished by the belief that the world is dangerous. Results suggest previous research relied on a measure highlighting dangers conservatives fear and neglecting dangers liberals fear, when both perceive the world as almost equally dangerous (8 samples; total N=3,734). A novel account of political ideology is proposed based on more predictive primals. Chapter II discusses how primals might develop. The author distinguishes retrospective theories—where primals reflect the content of past experiences—from interpretive theories—where primals act as lenses for interpreting experiences while remaining uninfluenced by them—and suggests twelve ways each theory’s relative merit can be empirically tested. A novel comprehensive framework for considering experiences in relation to any new construct is also proposed. Chapter III explores primals’ wellbeing-related correlates. By showing that many parents aim to teach negative primals to their children, some prevalence for meta-beliefs (i.e., beliefs about beliefs) associating negative primals with positive outcomes is established. Study 2 tests these meta-beliefs in six samples (total N=4,535) in regards to eight outcomes: job success, job satisfaction, emotion, depression, suicide, physical health, life satisfaction, and flourishing. Results indicate that negative primals are almost always associated with modestly to dramatically worse outcomes, across and within professions. In addition to filling a literature gap, and establishing bases for future comparison studies, findings could be used to strengthen interventions by undermining counterproductive meta-beliefs. Findings also underscore the urgent need for further research on the impact of primal world beliefs—teaching children or anyone that the world is a bad place in order to protect or prepare them may be ill-advised.
... In men, physical features, such as a V-Shaped torso, upper-body mass, and muscularity, are associated with good genes, as they are an indirect indicator of testosterone's immunosuppressant features in which high-quality men can afford to display them. Research investigating sexually dimorphic features in men have relied on metrics such as waist to chest (Fan, Dai, Liu, & Wu, 2005;Swami & Tovee, 2005) and shoulder to hip ratios (Braun & Byran, 2006;Buunk & Dijkstra, 2005;Hughes & Gallup, 2002), as these features have been associated with higher levels of testosterone (Folstad & Karter, 1992;Kasperk et al., 1997), immunocompetence, strength, and dominance (Dixson & Brooks, 2013;Dixson et al., 2014;Lassek & Gaulin, 2009). Women's attraction to these body types has suggested that there are preferences for men displaying increased upper-body mass and decreased fat in the abdomen (Dixson et al., 2014;Fan et al., 2005;Garza, Heredia, & Cieslicka, 2017;Garza & Byrd-Craven, 2019;Hughes & Gallup, 2002;Maisey et al., 1999;Pazhoohi, Garza, Doyle, Macedo, & Arantes, 2019). ...
Article
Full-text available
Women’s mating strategies are dependent on multiple factors, such as identifying which men advertise physical features indicating high genetic quality, as well as identifying which men are willing to invest in offspring. Research has suggested that women pursuing short-term mating prioritize physical attraction to facilitate the acquisition of good genes. Although it is known that physical characteristics are important in mate choice, research investigating the saliency of physical features in assessing male fitness has not been readily explored. The current study used an eye-tracking paradigm to investigate the role of short-term mating in women and their attraction and visual attention to men’s waist to chest ratios (WCRs). Women’s short term mating orientation (N = 130) was associated with attraction to men with low WCRs; however, their visual attention was not influenced by their mating strategy. Interestingly, women who perceived themselves as attractive rated men with low WCRs as more attractive and allocated attentional resources to physical features important in mate choice, such as the head and midriff region. The findings from this study lend some support to sexual strategies theory (Buss & Schmitt, 1993) and strategic pluralism (Gangestad & Simpson, 2000), and they suggest that mate preferences may be calibrated as a function of one’s mate value.
... The increasing performance gap between males and females as upper body strength becomes more critical for performance is likely explained to a large extent by the observation that males have disproportionately greater strength on their upper compared to lower body, while females show the inverse 42,43 . This different distribution of strength compounds the general advantage of increased muscle mass in upper body dominant disciplines. ...
Preprint
Sex dimorphism starts during early embryogenesis and is further manifested in response to hormones during puberty. As this leads to physical divergence that is measurably different between sexes, males enjoy physical performance advantages over females within competitive sport. While this advantage is the underlying basis of the segregation into male and female sporting categories, these sex-based categories do not account for transgender persons who experience incongruence between their biological sex and their experienced gender identity. Accordingly, the International Olympic Committee determined criteria by which a transgender woman may be eligible to compete in the female category, requiring total serum testosterone levels to be suppressed below 10 nmol/L for at least 12 months prior to and during competition. Whether this regulation removes the male performance advantage has not been collectively scrutinized. Here, we aim to review how differences in biological characteristics between biological males and females affect sporting performance and assess whether evidence exists to support the assumption that testosterone suppression in transgender women removes the male performance advantage. In this review, we report that the performance gap between males and females amounts to 10-50% depending on sport. The performance gap is more pronounced in sporting activities relying on muscle mass and strength, particularly in the upper body. Longitudinal studies examining the effects of testosterone suppression on muscle mass and strength in transgender women consistently show very modest changes, where the loss of lean body mass, muscle area and strength typically amounts to approximately 5% after 1 year of treatment. Thus, current evidence shows that the biological advantage enjoyed by transgender women is only minimally reduced when testosterone is suppressed. Sports organizations may therefore be compelled to reassess current policies regarding participation of transgender women in the female category of sport.
... Vocal fold dimorphism is one of the largest anatomical sex differences observed in humans (approximately 5 standard deviations 28,56 ) and greater than any other extant ape 57 . Cisgender men and women differ by 60% in vocal fold length 30 but only 8% in height 58 . Because vocal sexual dimorphism is extensive and, importantly, features little overlap in gender-typical vocal ranges, it is extremely difficult to speak in a voice consistent with the opposite sex, particularly in a sustained fashion 31 . ...
Article
Full-text available
Voice is one of the most noticeably dimorphic traits in humans and plays a central role in gender presentation. Transgender males seeking to align internal identity and external gender expression frequently undergo testosterone (T) therapy to masculinize their voices and other traits. We aimed to determine the importance of changes in vocal masculinity for transgender men and to determine the effectiveness of T therapy at masculinizing three speech parameters: fundamental frequency (i.e., pitch) mean and variation ( f o and f o -SD) and estimated vocal tract length (VTL) derived from formant frequencies. Thirty transgender men aged 20 to 40 rated their satisfaction with traits prior to and after T therapy and contributed speech samples and salivary T. Similar-aged cisgender men and women contributed speech samples for comparison. We show that transmen viewed voice change as critical to transition success compared to other masculine traits. However, T therapy may not be sufficient to fully masculinize speech: while f o and f o -SD were largely indistinguishable from cismen, VTL was intermediate between cismen and ciswomen. f o was correlated with salivary T, and VTL associated with T therapy duration. This argues for additional approaches, such as behavior therapy and/or longer duration of hormone therapy, to improve speech transition.
... 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). ...
Article
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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. ...
Article
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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. ...
Article
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. ...
Article
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.
... 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). ...
Article
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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). ...
Article
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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. ...
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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). ...
Article
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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). ...
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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]. ...
Article
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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). ...
Article
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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 ...
Article
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. ...
Article
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]. ...
Article
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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). ...
Article
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.
Chapter
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.
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Sexual selection researchers have traditionally focused on adult sex differences; however, the schedule and pattern of sex-specific ontogeny can provide insights unobtainable from an exclusive focus on adults. Recently, it has been debated whether facial width-to-height ratio (fWHR; bi-zygomatic breadth divided by midface height) is a human secondary sexual characteristic (SSC). Here, we review current evidence, then address this debate using ontogenetic evidence, which has been under-explored in fWHR research. Facial measurements collected from males and females aged 3 to 40 (Study 1; US, n=2449), and 7 to 21 (Study 2; Bolivia, n=179) were used to calculate three fWHR variants (which we call fWHRnasion, fWHRstomion, and fWHRbrow) and two other common facial masculinity ratios (facial width-to-lower-face-height ratio, fWHRlower, and cheekbone prominence). We test whether the observed pattern of facial development exhibits patterns indicative of SSCs, i.e. differential adolescent growth in either male or female facial morphology leading to an adult sex difference. Results showed that only fWHRlower exhibited both adult sex differences as well as the classic pattern of ontogeny for SSCs—greater lower-face growth in male adolescents relative to females. fWHRbrow was significantly wider among both pre- and post-pubertal males in the 2D sample; post-hoc analyses revealed that the effect was driven by large sex differences in brow height, with females having higher placed brows than males across ages. In both samples, all fWHR measures were inversely associated with age; that is, human facial growth is characterized by greater relative growth in the mid-face and lower face relative to facial width. This trend continues even into middle adulthood. BMI was also a positive predictor of most of the ratios across ages, with greater BMI associated with wider faces. Researchers collecting data on fWHR should target fWHRlower and fWHRbrow and should control for both age and BMI.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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We have studied the effect of a pharmacological dose of testosterone enanthate (3 mg.kg-1.wk-1 for 12 wk) on muscle mass