1. Department of Anthropology and Center for Population Biology, University of California, Davis, CA 95616, USA.
2. Santa Fe Institute and University of Siena, Santa Fe, NM 87501, USA.
3. International University College of Turin, 10121 Turin, Italy.
4. Graduate Group in Ecology, University of California, Davis, CA 95616, USA.
5. Department of Economic and Social Affairs, United Nations, New York, NY 10017, USA.
6. Department of Economics, University of California, Davis, CA 95616, USA.
7. Center for Economic Performance, London School of Economics, London WC2A 2AE, UK.
8. Integrative Anthropological Sciences Program, University of California, Santa Barbara, CA 93106, USA.
9. School of Human Evolution and Social Change, Arizona State University, Tempe, AZ 85281, USA.
10. Department of Anthropology, University of New Mexico, Albuquerque, NM 87131, USA.
11. Department of Anthropology, Northwestern University, Evanston, IL 60208, USA.
12. Department of Anthropology, University of Washington, Seattle WA 98195, USA.
13. School of Natural Resources and Environment, University of Michigan, Ann Arbor, MI 48109, USA.
14. Department of Anthropology, Florida State University, Tallahassee, FL 32306, USA.
15. Harvard Academy for International Studies, Harvard University, Cambridge, MA 02138, USA.
16. Carolina Population Center, University of North Carolina, Chapel Hill, NC 27516, USA.
17. 100 Tunney's Pasture Driveway, Ottawa, ON K1A 0T6, Canada.
18. Department of Anthropology, Washington State University, Pullman, WA 99164, USA.
19. Department of Social Policy, London School of Economics, London WC2A 2AE, UK.
20. Department of Anthropology, University of Missouri, Columbia, MO 65211, USA.
21. Department of Anthropology, University of Washington, Seattle, WA 98195, USA.
22. Department of Anthropology, University of Utah, Salt Lake City, UT 84112, USA.