To scrounge or not to scrounge? An evolutionary game-theoretical result on the integration of marginalist food-sharing models

Abstract

Abstract Behavioral ecologists believe that a substantial portion of variability in observed human food transfers derive from marginal value asymmetries in resource acquisition and can be explained with the help of tolerated scrounging, kin selection and reciprocal exchange models. For this belief to be true, however, it must be shown whether and to what extent these models might be integrated into a coherently unified explanation of resource sharing behavior. In this contribution, I combine marginalist analysis with evolutionary game theory to show that, contrary to the conventional view, these models cannot be usefully integrated. Given the option to scrounge a producer's acquisition or respect her ownership, natural selection should predispose individuals to adopt a pure scrounging strategy that leads to the equalization of marginal value differences in consumption. Reviewing the empirical evidence with a focus on recent agent-based models that illuminate the complex dynamics of scrounging behavior, I show that the pure scrounging equilibrium hypothesis is (i) able to predict node-level data describing the scale and scope of food transfers, (ii) consistent with dyad-level data indicating kin and contingency biases in food transfers, and (iii) supported by the apparent lack of a production-consumption correlation across small-scale communities.