Exponential random graph modeling (ERGM) is used here to test hypotheses derived from human behavioral ecology about the adaptive nature of human food sharing. Respondents in all (n=317) households in the fishing and sea-hunting village of Lamalera, Indonesia were asked to name those households to whom they had more frequently given (and from whom they had more frequently received) food during the preceding sea-hunting season. The responses were used to construct a social network of between-household food-sharing relationships in the village. The results show that kinship, proximity, and reciprocal sharing all strongly increase the probability of giving food to a household. The effects of kinship and distance are relatively independent of each other, while reciprocity is more common among residentially and genealogically close households. The results show support for reciprocal altruism as a motivation for food sharing while kinship and distance appear to be important partner-choice criteria.Keywords food sharing; cooperation; reciprocity; kin selection; social network analysis; ERGM Food sharing is an example of an apparently altruistic behavior: those who give food provide a benefit to others at a cost to themselves. Under most circumstances it should be difficult for natural selection to promote the evolution of such behaviors, as, all else being equal, those who undertake altruistic acts towards others will do worse than those who reap the rewards of others' altruism without paying its costs (Hamilton 1963). Yet apparently altruistic behaviors such as food sharing can evolve, and a number of adaptive mechanisms have been proposed to explain how natural selection might favor the evolution of such behaviors. By studying the adaptive significance of food sharing, we hope to learn something about the evolution of altruistic behaviors more generally (Kaplan and Hill 1985, Smith 1988, Winterhalder 1997, Gurven 2004a.In reconstructing the behavioral evolution of our species, food sharing has often been viewed as part of a suite of interrelated adaptations including hunting, central-place foraging, the sexual division of labor, and the nuclear family (Washburn & Lancaster 1968;Isaac 1978;Parker and Gibson 1979;Lovejoy 1981; McGrew and Feistner 1992). According to this view, differences in reproductive constraints between the sexes led to a sexual division of labor, with males pursuing high-variance meat resources and females pursuing more predictably acquired vegetal resources. Variance in meat acquisition favored sharing of meat within the group, and nutrient complementarity of animal and plant foods favored exchange of food between males and females. This in turn led to the establishment of the NIH Public Access
Author ManuscriptHum Nat. Author manuscript; available in PMC 2011 October 1.
NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript human pair-bond and the nuclear family, with female sexual fidelity coevolving with paternal investment in offspring.A competing view questions el...