Abstract # 3212 Event # 128:

Scheduled for Sunday, September 18, 2011 11:00 AM-11:15 AM: Session 17 (Meeting Room 408) Oral Presentation


THE EVOLUTION OF NON-KIN FOOD SHARING AMONG NON-HUMAN PRIMATES: PARTNER CHOICE, SOCIAL BONDS, AND RECIPROCAL EXCHANGE

A. V. Jaeggi1,2 and C. P. van Schaik1
1University of Zurich, Anthropological Institute and Museum, Winterthurerstr. 190, Zurich 8057, USA, 2Integrative Anthropological Sciences, University of California Santa Barbara, Santa Barbara CA 93106-3210
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     Food sharing is relatively common among primates but the vast majority of transfers are passive, suggesting inducement by harassment. However, harassment models alone fail to explain sharing among unequal social partners, such as dominants and subordinates, where the physical costs inflicted by harassment are minimal. Hence, we suggest that the social costs of not sharing explain its occurrence among such partners. In particular, we predict that owners should tolerate harassment by allies or potential mates, who could provide or withhold coalitionary support or matings in the future and sharing should thus co-evolve with opportunities for partner choice. We tested this hypothesis in a sample of 68 primate species using phylogenetic analyses based on both maximum likelihood and Bayesian approaches. We also included possible constraints namely the pre-existence of sharing in the mother-offspring context and diet, and controlled for kinship. We found strong evidence that (i) food sharing among adults was derived from sharing with offspring, and that (ii) sharing within the sexes co-evolved with the formation of same-sex coalitions and sharing between the sexes with the opportunity for female mate choice. These results provide comparative support for the hypothesis that food is “traded” for coalitionary support and matings. Based on our results, we predict that sharing should occur wherever partner choice is important and review evidence for this in species not included in our sample.