The evolution of food sharing in primates

Abstract

The aim of this study is to explain the occurrence of food sharing across primates. Defined as the unresisted transfer of food, evolutionary hypotheses have to explain why possessors should relinquish food rather than keep it. While sharing with offspring can be explained by kin selection, explanations for sharing among unrelated adults are more controversial. Here we test the hypothesis that sharing occurs with social partners that have leverage over food possessors due to the opportunity for partner choice in other contexts. Thus, we predict that possessors should relinquish food to potential mates or allies, who could provide or withhold matings or coalitionary support in the future. We used phylogenetic analyses based on both maximum likelihood and Bayesian approaches in a sample of 68 primate species to test these predictions. The analyses strongly indicate that (1) sharing with offspring is predicted by the relative processing difficulty of the diet, as measured by the degree of extractive foraging, but not overall diet quality, (2) food sharing among adults only evolved in species already sharing with offspring, regardless of diet, and (3) male-female sharing co-evolved with the opportunity for female mate choice and sharing within the sexes with coalition formation. These results provide comparative support for the hypothesis that sharing is "traded" for matings and coalitionary support in the sense that these services are statistically associated and can thus be selected for. Based on this, we predict that sharing should occur in any species with opportunities for partner choice. The aim of this study is to explain the occurrence of food sharing across 26 primates. Defined as the unresisted transfer of food, evolutionary hypotheses have to 27 explain why possessors should relinquish food rather than keep it. While sharing with 28 offspring can be explained by kin selection, explanations for sharing among unrelated 29 adults are controversial. Here we test the hypothesis that sharing occurs with social 30 partners that have leverage over food possessors due to the opportunity for partner 31 choice in other contexts. Thus, we predict that possessors should relinquish food to 32 potential mates or allies, who could provide or withhold matings or coalitionary support 33 in the future. We used phylogenetic analyses based on both maximum likelihood and 34Bayesian approaches in a sample of 68 primate species to test these predictions. The 35 analyses strongly indicate that (i) sharing with offspring is predicted by the relative 36 processing difficulty of the diet, as measured by the degree of extractive foraging, but 37 not overall diet quality, (ii) food sharing among adults only evolved in species already 38 sharing with offspring, regardless of diet, and that (iii) male-female sharing co-evolved 39 with the opportunity for female mate choice and sharing within the sexes with coalition 40 formation. These results provide comparative support for the hypothesis that sharing is 41 "traded" for matin...

Human origins and the transition from promiscuity to pair-bonding

“…Population genetic models tell us, however, that even weak evolutionary forces can result in dramatic phenotypic or behavioral changes if they act over multiple generations. A recent metaanalysis (53) shows correlation between male-to-female food transfer and the opportunity for female mate choice. There are some additional anatomical features of humans-bipedalism, hidden ovulation, and permanently enlarged mammary glands-that are easier to explain in terms of the pair-bonding model than the mate-guarding and communal breeding models (5,54).…”

Reciprocity explains food sharing in humans and other primates independent of kin selection and tolerated scrounging: a phylogenetic meta-analysis

“…We gathered all quantitative studies that tested for a statistical relationship between food given and food and/or other commodities received in human foragers and primates, building on previous comprehensive review work [17,18,26,35] as well as searches of subsequent literature. This search identified 25 studies, all of which focused on sharing among adult individuals.…”

The evolution of altruistic social preferences in human groups

“…Social grooming, alloparental care, coalitionary support and territorial defence are widely distributed across the primate order. Food sharing among adults only occurs regularly in chimpanzees (Pan troglodytes; [19]). The costs of most forms of altruistic behaviours are probably fairly low.…”