Sex and food control in the “uncommon chimpanzee”: How Bonobo females overcome a phylogenetic legacy of male dominance

Abstract

Inferences for female bonding in humans have drawn on models derived from studies of nonhuman primates. In primates, strong affiliative relationships between unrelated females are rare. This is true for the social systems of apes and particularly for those of the closest living relatives of humans, the chimpanzee ( Pan troglodytes). However, the other member of the genus Pan, the bonobo ( Pan paniscus) is strikingly different in this regard as evidenced from the present comparative study that was conducted at the Wilhelma Zoo, Germany. A group of bonobos and of chimpanzees was each provided with limited access to an artificial “fishing” site (a simulated termite mound) filled with desirable food. In chimpanzees, the adult male was dominant over all females and able to monopolize the food. In bonobos, on the other hand, the adult bonobo male was low ranking, and females controlled food access. Sex between bonobo females apparently facilitated affiliative encounters between females in the context of feeding. Until now, studies of exchanges of sex-for-food focused on heterosexual interactions. This study reveals that trading of sex for food occurs regularly between bonobo females. These exchanges appear to reduce tension and facilitate female cofeeding and cooperation. They help create stable long-term relationships among females that result in coalition formation, control of food resources, and ability to elevate their dominance status relative to males well above that of their chimpanzee counterparts. The strong affiliative relationships between unrelated female bonobos provide an alternative model from which predictions for bonding among human females can be generated.