Date of this Version
Published in Evolution and Human Behavior 40 (2019), pp 249–258.
Sociosexuality is defined as an individual's interest in uncommitted sexual activity and can be measured in terms of both psychological orientations and behavioral expression. In socio-ecological contexts in which adults monogamously partner and cooperate to raise children, individuals with unrestricted sociosexuality are likely to prioritize mating/competition over committed partnering and parenting. Given the importance of mother-father cooperation in the evolutionary past, humans may have the capacity to facultatively and opportunistically downregulate sociosexuality to focus on priorities related to invested partnering and parenting. To date, no prior studies have used longitudinal data to track within-individuals changes in sociosexuality as it relates to such life history transitions. Given the lack of prior longitudinal research in this area, it is likewise unknown what physiological mechanisms might mediate within-individual changes in sociosexuality through time but testosterone is a plausible candidate. To explore these questions, we drew on a large, long-running study of Filipino men (n=288), who were single non-fathers at 25.9 years of age and were followed up 4–5 years later. We found that men with more unrestricted sociosexuality at baseline were more likely to experience relationship dissolution by follow-up, consistent with past work. Compared to men who remained single non-fathers at follow-up, men who became married residential fathers showed shifts towards more restricted global sociosexuality as well as sociosexual behavior. Relative to their own baseline values, married residential fathers also had more restricted sociosexuality in all domains at follow-up. They were the only group for whom this was found. We found theoretically-consistent but modest support for positive correlations between men's testosterone and their sociosexuality, but no evidence that the two change in tandem together through time. Our results suggest that some amount of between-individual differences in sociosexuality are not stable and can facultatively shift alongside other aspects of male reproductive effort.