Paternity and father-offspring relationships in wild chimpanzees, Pan troglodytes schweinfurthii.

Abstract

Hamilton's seminal theory of kin selection asserts that because relatives share a certain proportion of genes, individuals can increase their inclusive fitness by helping and/or not harming kin, as long as the benefits to kin outweigh the costs to the individual. We would expect animals to attain maximal inclusive fitness by discriminating both the available maternal and paternal kin from non-kin in their social groups. The primate order is a useful taxon in which to study kin selection and kin discrimination because most primates live in permanent social groups with both kin and non-kin between which to discriminate, and their complex social interactions provide many opportunities to both hurt and aid others. However, the prevailing view has been that the discrimination of paternal kin does not occur in most species. Despite emerging studies that suggest otherwise, study of paternal kin discrimination thus far has been limited in primates. Furthermore, study has been restricted to matrilineal species with male-biased dispersal. Paternal kinship could also be important in a patrilineal species such as chimpanzees as males will remain with fathers and other paternal kin for life, as will females until they disperse. Thus, this study aimed to further our understanding of importance of paternal kinship in social behavior by examining the most direct paternal relationship, that of fathers and offspring, in the chimpanzees of Gombe National Park, Tanzania. Identifying fathers and offspring and characterizing their relationship is a necessary first step on the way to testing for kin discrimination amongst non-descendent paternal kin. Thus, in Chapter 1, I first determined paternal relationships and explored patterns of male reproductive success relative to dominance rank and the priority of access model, as well as fathers' mating strategy and age. Then in Chapter 2, I examined whether fathers showed parental investment in their juvenile and adolescent sons. Finally, in Chapter 3, I investigated whether there was inbreeding avoidance between fathers and daughters.