1. School of Mathmatical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK
2. Department of Anthropology, Hunter College, City University of New York, NY 10065-5024, USA
3. Program in Anthropology, The Graduate Center, City University of New York, NY 10016-4309, USA
4. Program in Biology, The Graduate Center, City University of New York, NY 10016-4309, USA
5. New York Consortium in Evolutionary Primatology New York, NY, USA
6. Department of Anthropology, University College London, 14 Taviton Street, London WC1H 0BW, UK
7. Department of Anthropology, The Field Museum, 1400 S. Lake Shore Drive, Chicago 60605-2496, IL, USA
8. Department of Biology, University College London, Gower Street, London WC1E 6BT, UK
9. Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, UK