Affiliation: | ∗ Department of Biology, University of Pennsylvania, Philadelphia, PA, U.S.A. † Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, U.S.A. ‡ Department of Anthropology, Emory University, Atlanta, GA, U.S.A. § Moremi Baboon Project, Maun, Botswana, U.S.A. ∗∗ Department of Psychology, University of Pennsylvania, Philadelphia, PA, U.S.A. |