1. Department of Human Evolutionary Biology; Harvard University; Cambridge MA 02138 USA
2. School of Natural Sciences; Trinity College Dublin; College Green Dublin Ireland
3. Trinity Centre for Biodiversity Research; Trinity College Dublin; Dublin Ireland
4. Courant Research Center Evolution of Social Behavior; Georg-August-Universität Göttingen; Kellnerweg 6 37077 Göttingen Germany
5. Harvard School of Public Health; 677 Huntington Avenue Boston MA 02115 USA