1. Department of Ecology, Evolution and Organismal Biology, Iowa State University, Ames, IA 50011, USA.
2. Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 88001, USA.
3. Institute of Primate Research, National Museums of Kenya, Nairobi, Kenya.
4. Department of Anthropology, University of North Carolina, Charlotte, NC 28223, USA.
5. Department of Ecology, Evolution and Environmental Biology, Columbia University, New York, NY 10027, USA.
6. Department of Anthropology, University of Calgary, Calgary, T2N 1N4 Canada.
7. Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA.
8. The Dian Fossey Gorilla Fund International and Zoo Atlanta, Atlanta, GA 30315, USA.
9. Department of Biology, Duke University, Durham, NC 27708, USA.
10. Department of Anthropology, University of Wisconsin-Madison, Madison, WI 53706, USA.