The Curious Naturalist Seminar Series

Dr. Joan Silk November 10, 2011

Joan Silk
Department of Anthropology
Center for Society and Genetics
Center for Behavior, Evolution and Culture
University of California, Los Angeles

"What are friends for? The adaptive value of social bonds"

Group living has evolved in many animal taxa, but humans and other primates are unusual because individuals establish close and lasting social bonds with other members of their groups. Such bonds are particularly pronounced among females in species like baboons, in which females’ social lives revolve around a tight core of close associates, who are mainly close maternal relatives. Data derived from long-term studies of female baboons at several sites in Africa suggest that social bonds help females cope more effectively with the stresses of everyday life. In addition, females that have close and stable social bonds reproduce more successfully and live longer than others. These findings closely parallel evidence that social ties have positive effects on physical and mental health in humans. As with baboons, the strength and quality of these bonds are more important than their number. Although we are not yet certain whether the mechanisms that underlie these effects in humans and other primates are the same, it seems likely that the capacity and motivation to establish and nurture close social relationships with others have been under strong selective pressure in the primate lineage for many millions of years.


Prof. Silk studies the evolution of social behavior in primates. Her field research focuses on the social lives and reproductive strategies of primate females, informed by fieldwork on baboons in Kenya and Botswana. Her recent work includes long-term evaluation of the structure and adaptive function of close social bonds among female baboons, experimental studies of the phylogenetic roots and ontogenetic development of pro-social preferences, and comparative analyses of the evolutionary forces that shape primate sex ratios.

Prof. Silk was awarded a B.A. with honors in Anthropology at Pitzer College in Claremont, California, and went on to earn an MA and PhD at the University of California, Davis. After postdoctoral research at the University of Chicago, she joined the faculty in Anthropology at UCLA in 1986 where she is now a Full Professor. The author of more than 100 papers published in scientific journals or as contributions to volumes of collected works, Dr. Silk is also the co-author (with Robert Boyd) of How Humans Evolved, which was originally published by W.W. Norton in 1997 and has subsequently appeared in five revised editions and been translated into French, Spanish, and Japanese.