Fathers enhance social bonds among paternal half-siblings in immature olive baboons (Papio hamadryas anubis)

Abstract

A universal aspect of mammalian sociality is substantive, core relationships among relatives. Although comparative studies of nonhuman primates have clarified the adaptive importance of kinship, previous research has focused primarily on maternal relatives. To rectify this gap in the literature, recent work has begun to examine the social and adaptive consequences of paternal kinship. However, among multimale-multifemale species, particularly Old World primates, there have been conflicting reports describing the social bonds among paternal relatives. Some researchers have suggested that this inconsistency results from the availability of preferred relatives (maternal kin) as social partners. To explore this hypothesis, we examine the relationship between the availability of kin and sociality among immature olive baboons (Papio hamadryas anubis) by considering the effects that parents have on the social bonds among young maternal and paternal half-siblings. We found that while the presence of a mother in the group did not affect social bonds among immatures, the presence of a father did have a significant impact. Compared to immatures whose fathers were absent from the group, individuals with a father present maintained stronger bonds with paternal half-siblings. These data may help explain some of the variation in previous results among different studies examining the social bonds of half-siblings. Furthermore, our study suggests that the development of relationships among paternal half-siblings is facilitated by fathers and that relationships with paternal kin may be just as critical as those with maternal kin. This study indicates that even in a social system in which matrilineal kinship powerfully influences group structure and dynamics, paternal kinship may nevertheless form the basis of significant selective forces in social evolution.