Applying socioendocrinology to evolutionary models: Fatherhood and physiology

Abstract

Owing to humans' unique life history pattern, particularly comparatively short interbirth intervals, early weaning, and prolonged support of multiple dependents, human females have greater reproductive value and higher lifetime fertility, on average, than do their Great Ape counterparts. As hominin females began weaning their young early and "stacking" dependents of various ages, they must have had cooperative allomaternal care partners already in place or been successful at concurrently soliciting help to ensure a high rate of survival of their offspring. Following Hrdy, I define allomaternal care (and its derivatives, such as "allomothers" and "allomothering") as "care from anyone other than the mother," which thus encompasses a wide range of individuals, including fathers. Who the likely allomother candidates mothers were and what form that cooperation took remain intriguing, difficult-to-answer questions, which are limited, in some capacity, by the lines of evidence available to us. Here, I present a framework for the ways in which we can integrate neurobiological-endocrine and social-behavioral data ("socioendocrinology") to contribute to this dialogue in terms of evaluating fathers' roles.

Testosterone and human behavior: the role of individual and contextual variables

“…Thus, paternal care is associated with lowering of testosterone levels [18,19]. There are also differences in the extent to which individual men prioritize parental or mating behavior, and this is correlated with their testosterone levels [5].…”

Evolving the neuroendocrine physiology of human and primate cooperation and collective action

“…The neuroendocrine physiology of OT was co-opted for numerous behaviours associated with maternal care including the regulation of the amount of care given by mothers and demanded [20,21], macaques [22], marmosets [23] [9, 13,24,25] intergroup interactions [26,27] testosterone paternal care marmosets [28], not titi monkeys [29] [16] pair bond [16] in-group [30] [31] out-group chimpanzees [32] [33] no effect [34] intrasexual competition chimpanzees [35], baboons [36], colobus monkeys [37], not bonobos [38] [ 39,40] [ 31] rstb.royalsocietypublishing.org Phil. Trans.…”

“…(a) Testosterone, parenting and pair-bonding While OT tends to increase during parenting, many species, including humans, show decreases in testosterone [16,99]. Higher levels of testosterone are correlated with mating effort in seasonally breeding [100,101] and non-seasonally breeding primates [16,35].…”

“…Higher levels of testosterone are correlated with mating effort in seasonally breeding [100,101] and non-seasonally breeding primates [16,35]. Engaging in mate competition, mate guarding and courtship takes a significant amount of time and energy.…”

Salivary oxytocin increases concurrently with testosterone and time away from home among returning Tsimane’ hunters

“…Hunting and meat sharing are ancient contexts of male status competition, parental investment and reciprocal cooperation [17], and therefore well suited to reveal evolved endocrine mechanisms underlying male strategies [1,12,13,16].…”