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

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.