Origins of Prosocial Preferences

We vote, recycle, give blood, and volunteer for committee assignments. The beneficiaries of these altruistic acts are often strangers, that we will never meet. This kind of behavior is motivated by empathy and concern for the welfare of others. What are the phylogenetic roots of prosocial preferences? To answer this question, my colleagues and I have begun a series of experiments with chimpanzee and children to evaluate their responses when given the opportunity to provide benefits to others.

Adaptive variation in primate sex ratios

Do female primates adjust the sex ratio of their offspring in relation to their own rank? The primate literature presents conflicting evidence about this question. To make sense of this body of data, Gillian Brown and I have conducted a series of meta-analyses of sex ratio biases in primate groups. Our results suggest that observed biases are the product of stochastic variation in small samples. However, comparative analyses show that local resource competition and local resource enhancement influence species-level sex ratios.

What are friends for?

For humans, and perhaps for other primates, the capacity to form and maintain close social bonds has an important impact on health and happiness. Human friendships seem to transcend the calculus of kin selection or reciprocity. This kind of relationship defies the logic of evolutionary theory, but seems to play an important role in our lives.I am interested in the evolution of these kinds of relationships in humans and other primates.

The structure and function of social bonds

I have studied yellow baboons in Amboseli, Kenya and chacma baboons in the Okavango Delta, Botswana Analyses of long-term data from both of these sites indicates that females form strong, supportive, equitable, and enduring bonds with selected partners, particularly close maternal kin and peers, who may be paternal half siblings. At both sites, the most sociable females have the highest survivorship among their offspring. For females, social bonds have adaptive value.