Gorillas in Our Midst? Human Sexual Dimorphism and Contest Competition in Men

Hill, Alexander K.; Bailey, Drew H.; Puts, David A.

doi:10.1016/b978-0-12-420190-3.00015-6

Cited by 36 publications

(45 citation statements)

References 142 publications

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“…These trends are consistent with changes seen in domestication syndrome, leading multiple authors to suggest that Homo sapiens has undergone a physiological process of selfdomestication (Cieri et al, 2014;Franciscus, Maddux, & Schmidt, 2013;Groves, 1999;Hare, 2017;Leach, 2003;Wrangham, 2018Wrangham, , 2019bWrangham, , 2019a. Perhaps the most indicative shifts include declines in body size and body size sexual dimorphism (Frayer, 1980;Frayer & Wolpoff, 1985;Gallagher, 2013;Hill et al, 2017;Ruff, 2002;Ruff et al, 1997;Ryan & Shaw, 2015), although teeth and cranial size and shape also show comparatively less sexual difference in contemporary populations (Brace & Ryan, 1980;Frayer & Wolpoff, 1985). In addition, there has been marked reduction in skeletal robusticity (Ryan & Shaw, 2015), Lieberman, 2011; C. Liu et al, 2014;McHenry, 1994;Ruff et al, 1997;Wiercinski, 1979).…”

Section: Signs Of Domestication In Recent Humansmentioning

confidence: 70%

“…From the Mid-Pleistocene, human evolution has involved substantial decline in several sexually dimorphic features, suggesting reductions in relative masculinity and a shift towards a more gracile ('feminised') morphology (Brace & Ryan, 1980;Cieri et al, 2014;Frayer, 1980;Frayer & Wolpoff, 1985;Hill, Bailey, & Puts, 2017;Ruff, Trinkaus, & Holliday, 1997). These trends are consistent with changes seen in domestication syndrome, leading multiple authors to suggest that Homo sapiens has undergone a physiological process of selfdomestication (Cieri et al, 2014;Franciscus, Maddux, & Schmidt, 2013;Groves, 1999;Hare, 2017;Leach, 2003;Wrangham, 2018Wrangham, , 2019bWrangham, , 2019a.…”

Section: Signs Of Domestication In Recent Humansmentioning

confidence: 99%

“…Each is likely to have varied over deep-time in response to differing socioecological contexts, and stages of human physical, cognitive, and social evolution. Increased reliance on social learning and a cooperative sociocultural niche [4][5][6][7][8] Group ostracism or execution of aggressive individuals [9][10][11][12] Group collaboration in inter-group hostilities 13,14 Negative Direct and physical male-male contest competition 15,16 Female selection in favour of masculine 'good genes' 17,18 Notes: 1 (Hrdy, 2009); 2 (Cieri et al, 2014); 3 (Kruger, 2006);4 (Cieri et al, 2014;Ellis, 2016;Hare, 2017;Sterelny, 2011Sterelny, , 2018; 5 (Ellis, 2016); 6 (Hare, 2017); 7 (Sterelny, 2011); 8 (Sterelny, 2018); 9 (Boehm, 2014); 10 (Wrangham, 2018); 11 (Wrangham, 2019a); 12 (Wrangham, 2019b); 13 (Alexander, 1990); 14 (Wrangham & Glowacki, 2012); 15 (Carrier & Morgan, 2015); 16 (Hill et al, 2017); 17 (Holzleitner & Perrett, 2017); 18 (Marcinkowska et al, 2019).…”

Section: Selection Against Masculinity In Humansmentioning

confidence: 99%

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Masculinity and the mechanisms of human self-domestication

Gleeson

2017

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Objectives:Pre-historic decline in human craniofacial masculinity has been proposed as evidence of selection for elevated sociability and a process of 'human self-domestication' thought to have promoted complex capacities including language, culture, and cumulative technological development. This follows experimental observation of similar changes in non-human animals under selection for reduced aggression. Two distinct domestication hypotheses posit developmental explanations, involving hypoplasia of embryonic neural crest cells (NCCs), and declining androgen influence, respectively. Here, I assess the operation and potential interactions between these two mechanisms and consider their role in enhanced human adaptation to a cooperative sociocultural niche. Methods: I provide a review and synthesis of related literature with a focus on physiological mechanisms effecting domesticated reductions in masculinity and sexual dimorphism.Further, I examine pre-historic modes of socio-sexual selection likely to drive human selfdomestication via reduced aggression and masculinity. Results:I find pluripotent NCCs provide progenitors for a wide range of vertebrate masculine features, acting as regular targets for sexually driven evolutionary change; suggesting domesticated hypoplasia of NCC-derived tissues would be sufficient to explain declines in masculine traits and features. However, lineage specific androgen receptor variability likely moderates these NCC-based effects. Conclusions:These findings extend theorised mechanisms driving noted physiological, morphological, and behavioural changes thought to indicate enhanced sociability and human and selfdomestication. Multiple current explanations for human sociability are consistent with physiological domestication under socio-sexual selection favouring dampened masculine physiology and behaviour as adaptations to an enhanced sociocultural niche. The analysis highlights multiple avenues for further investigation.Masculinity and the mechanisms of human self-domestication-Ben Gleeson 3

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Section: Signs Of Domestication In Recent Humansmentioning

confidence: 70%

Section: Signs Of Domestication In Recent Humansmentioning

confidence: 99%

Section: Selection Against Masculinity In Humansmentioning

confidence: 99%

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Masculinity and the mechanisms of human self-domestication

Gleeson

2017

Preprint

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“…Indeed, sexual ornaments are more variable in males and tend to be more sensitive to the overall growth of individual compared to other traits (23,24,26,27) . Traits such as tall height (28)(29)(30) , facial masculinity (31,32) , and deep voices (33)(34)(35)(36)(37) are often thought of as sexual ornaments in humans as they are perceived to be attractive to females (38) and intimidating to other males (35,(39)(40)(41) However, the evidence that these traits reflect the condition or quality of males in humans is ambiguous and inconsistent across studies (17,(42)(43)(44)(45) . Some of the inconsistency could be due to methodological limitations of previous studies such as small sample size, lack of correction for population structure, and the use of perceived measures of masculinity and attractiveness, which are likely influenced by socio-cultural factors that are difficult to control in observational studies.…”

Section: Introductionmentioning

confidence: 99%

Facial masculinity does not appear to be a condition-dependent male ornament in humans and does not reflect MHC heterozygosity

White

Mattern

et al. 2018

Preprint

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Facial masculinity is thought to be a condition-dependent male ornament, reflecting immunocompetence in humans. To test this hypothesis, we calculated an objective measure of facial masculinity/femininity using three-dimensional images in a large sample (N = 1,233) of people of European ancestry. We show that facial masculinity is positively correlated with adult height in both males and females. This suggests that variation in growth contributes, at least in part, to variation in facial masculinity, which is characteristic of condition-dependent traits. However, facial masculinity scales with growth similarly in males and females, suggesting that facial masculinity is not specifically a male ornament. Additionally, we measured immunocompetence via heterozygosity at the major histocompatibility complex (MHC), a well known genetic marker of immunity. We show that while height is positively correlated with MHC heterozygosity, facial masculinity is not. Thus, facial masculinity does not reflect immunocompetence measured by MHC heterozygosity in humans as thought previously. Overall, we find no support for the idea that facial masculinity is a condition-dependent male ornament that has evolved to indicate immunocompetence.

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“…Additionally, because testis maintenance requires a larger percentage of energetic resources in smaller species (e.g., in mammals10), production of large sperm may serve as an indication of underlying male quality in smaller species. Humans, though, are a large species whose males possess relatively small testes21 alongside a host of traits suggestive of an evolutionary past characterized largely by premating competition, particularly physical aggression or threats of physical aggression 22. By helping to unravel the big-sperm paradox, however, Lüpold et al .…”

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confidence: 99%

The long and the short of it: new insights on sperm length help demystify the complexities of sexual selection

Hill

Eisenberg

2016

Asian J Androl

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Human sperm are approximately 6000th of a centimeter long, a small fraction of a man's total body length. By contrast, fruit fly (Drosophila spp.) sperm can reach nearly 6 cm, roughly twenty times the total length of their bodies. This dramatic variation in male reproductive biology is explored in a recent paper from the journal Nature.1 While the literature on sperm competition has for decades emphasized the fitness benefit males of many species accrue by producing small gametes in large quantities, understanding species whose males produce large gametes in small quantities while remaining competitive for fertilizations has until recently proven more difficult. Stefan Lüpold and colleagues suggest a solution to this “big-sperm paradox.”

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Gorillas in Our Midst? Human Sexual Dimorphism and Contest Competition in Men

Cited by 36 publications

References 142 publications

Masculinity and the mechanisms of human self-domestication

Masculinity and the mechanisms of human self-domestication

Facial masculinity does not appear to be a condition-dependent male ornament in humans and does not reflect MHC heterozygosity

The long and the short of it: new insights on sperm length help demystify the complexities of sexual selection

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