Why men invest in non-biological offspring: paternal care and paternity confidence among Himba pastoralists

Abstract

Paternal investment is predicted to be a facultative calculation based on expected fitness returns and modulated by a host of social predictors including paternity uncertainty. However, the direct role of paternity confidence on the patterns of paternal investment is relatively unknown, in part due to a lack of research in populations with high levels of paternity uncertainty. Additionally, much of the work on paternity certainty uses cues of paternity confidence rather than direct assessments from fathers. We examine the effect of paternity assertions on the multiple measures of paternal investment in Himba pastoralists. Despite a high degree of paternity uncertainty, Himba have strong norms associated with social fatherhood, with men expected to invest equally in biological and non-biological offspring. Our behavioural data show patterns that largely conform to these norms. For domains of investment that are highly visible to the community, such as brideprice payments, we find no evidence of investment biased by paternity confidence. However, more private investment decisions do show some evidence of sex-specific titration. We discuss these results in light of broader considerations about paternal care and the mating–parenting trade-off.

The Role of Spousal Separation on Norms Related to Gender and Sexuality among Himba Pastoralists

“…However, this high rate of extra-pair paternity does not always lead to the titration of investment that evolutionary scholars would predict. Both experimental and observational evidence has shown that Himba men place great value on their role as social fathers, even when they suspect they are not the biological father (Prall and Scelza 2020b;Scelza et al 2020a). There is some evidence that spreading paternity across multiple partners positively impacts women's reproductive success, as women who have more children with lovers have overall greater fertility (Scelza 2011a).…”

“…Although we do not present data on child labor here, our previous findings lend support to this idea. Himba men have been shown to bias their investments in biological versus non-biological children, in what appears to be a functional response to their productive value (Prall and Scelza 2020b). Girls, who Himba resoundingly praise as being valuable laborers, have poorer anthropometric outcomes when they are believed to be omoka (non-biological offspring).…”

Are fathers a good substitute for mothers? Paternal care and growth rates in Shodagor children

“…Additionally, Shodagor children tend to be watched very closely until around the age of 5, at which point they are often considered proficient swimmers and no longer at risk of drowning, should they fall off of the boat. It is clear that Aka and Shodagor fathers' caregiving are serving different purposes, which is consistent with the facultative nature of human fatherhood, as well as the fact that fathers' contributions to their children vary a great deal across cultures, based on child age (e.g., Crittenden & Marlowe, 2008;Harkness & Super, 1992;Scelza, 2010;Shenk & Scelza, 2012;Shenk et al, 2013;Prall & Scelza, 2020;Winking et al, 2009). Despite limitations with our data, it is clear that Shodagor fathers provide very high levels of direct care for their young children during the dry season, and that fathers in trading households are the primary caregivers of their children more often than mothers, which is a pattern of care that has never before been documented in a subsistencebased society.…”

Evolutionary and Life History Insights into Masculinity and Warfare

“…What is of particular interest is that EPP is very transparent, with both men and women accurately detecting and accepting cases of EPP (women 72% accuracy; men 73%) (Scelza et al 2020b). The Himba express strong norms associated with fatherhood independent of biological paternity (Prall and Scelza 2020).…”