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

Abstract

Oxytocin, testosterone and cortisol can have opposing effects on social behaviour, yet few studies have examined their interactions. We measured changes in salivary oxytocin, testosterone and cortisol among Tsimane' men returning home after hunting, an ancient context of male status competition, parental investment and cooperation. Contra normal diurnal rhythm, oxytocin increased relative to baseline and this increase was positively associated with duration of the hunt and change in testosterone, but not cortisol, social context, hunting outcome or physical activity. The concurrent increase in endogenous peripheral oxytocin and testosterone is unexpected given their opposing independent effects on social cognition and behaviour, and has not been observed before. We discuss the potential significance of these effects for the biology of pair-bonding, parenting and social foraging in humans and other species.

Endogenous Testosterone and Exogenous Oxytocin Modulate Attentional Processing of Infant Faces

“…Hence, these results also suggest that the interaction between testosterone and oxytocin is sexually dimorphic. Another study, which investigated hormonal shifts in Tsimané hunters, found that both, endogenous oxytocin and endogenous testosterone, increased after hunting [22]. The authors presumed that the elevated testosterone levels might have resulted from successful hunting while the increase of oxytocin could enhance social salience.…”

“…The authors presumed that the elevated testosterone levels might have resulted from successful hunting while the increase of oxytocin could enhance social salience. Further suggesting an interaction between both hormones was the fact that the percentage of increase of both hormones was strongly correlated [22]. …”

“…In addition, lower baseline testosterone levels in those fathers were associated with more optimal paternal behavior [23]. Even though low testosterone levels as well as high oxytocin levels are usually linked to parental behavior [18,19,24–27] there might exist situations that lead to an increase of both hormones in order to modulate behavior (such as hunting-, protection-, or sexual-behavior) [22,23,26,27]. Nevertheless, a hormonal mechanism through interaction between testosterone and oxytocin that increases responsiveness to babies could be an adaptive feature that facilitates caretaking in adults and should thus enhance reproductive success.…”

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

“…OT can also augment Leydig cell testosterone production [127,128]. Studies in humans show that both testosterone and OT increase simultaneously in a range of activities from sexual activity [18], to hunting [46], to in-group/out-group competition [26,33], and that exogenous OT administration increased salivary testosterone levels and enjoyment from parenting in fathers [47] (though note that not all OT administration studies find concurrent increases in testosterone [129]). Taken at face value, this evidence may suggest the potential for OT and testosterone to work in concert to promote cooperative or coalitional behaviours.…”

“…The human feeding niche requires extensive bi-parental care, as well as additional multi-generational support, all of which would benefit from extensive tolerance by human males of both their offspring and other family members [45]. The anxiolytic and bonding aspects of increased OT may be a critical proximate mechanism that keeps human males engaged in familial provisioning [46].…”