Masculinity and the mechanisms of human self-domestication

Abstract

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

Masculinity and the Mechanisms of Human Self-Domestication

“…Further, such preferences appear to be enhanced under conditions of high pathogen presence (DeBruine, Jones, Crawford, Welling, & Little, 2010; and elevated social inequality (Brooks et al, 2010). These observations conform to expectations that women are adaptively predisposed to making context-dependent mating choices between males with either 'good genes' (and elevated masculinity), or those with a higher propensity for pair-bonding and paternal investment (Kruger, 2006;Little, Connely, Feinberg, Jones, & Roberts, 2011;Quist et al, 2012;Trivers, 1972).…”

“…Additionally, the nature of human intersexual selection provides a flourishing field with numerous contributors (Archer, 2009;Brooks et al, 2010;DeBruine, Jones, Crawford, et al, 2010;Feinberg et al, 2008;Kruger, 2006;Lee et al, 2015;Thornhill, Chapman, & Gangestad, 2013). The proposal that group ostracism and punishment could act as selection for domesticated sociability (Wrangham, 2014(Wrangham, , 2018) mirrors work by Boehm (2012Boehm ( , 2014 and Pinker (2011), among others.…”

From Physical Aggression to Verbal Behavior: Language Evolution and Self-Domestication Feedback Loop

“…Self-domestication in humans has been attributed to sexually selective forces, including selection against (physical) aggression, and in favor of pair-bonding beneficial for child rearing (Hare et al, 2012;Stanyon and Bigoni, 2014;Okanoya, 2015;Gleeson, 2018). Likewise, the emergence of early grammars, especially suited to verbal aggression (insult), has been attributed to sexual selection for creative cognitive abilities (Progovac and Locke, 2009;Progovac, 2015).…”

Natural/sexual selection: What’s language (evolution) got to do with it?

“…Sexual selection has been repeatedly invoked in the studies of human evolution, including in the recently postulated self-domestication hypothesis, which invokes selection against (physical) aggression, and in favor of prosociality and pair-bonding, considered to be beneficial for child rearing (e.g. Hare et al 2012;Stanyon and Bigoni 2014;Okanoya 2015;Gleeson 2018). 3 Likewise, relating specifically to language, the emergence of early grammars has been attributed to sexual selection, especially in the context of their utilization for insult and verbal aggression (Progovac and Locke 2009;Progovac 2015Progovac , 2016a.…”