Abstract
This study shows how non-individualistic preferences can be individual .tness maximizing in the presence of general equilibrium externalities. In the model, individuals share an endowment among themselves and use the proceeds either for immediate consumption or for the purchase of consumption goods from merchants on the external market if such exists. Assuming that increased consumption means increased individual .tness, inequity-averse behavior with respect to endowment distribution can be an optimal response to merchants.price discrimination and lead to the evolution of inequity-averse preferences. The .nding that members of a market-integrated society are more pro-social as compared to members of an isolated society is supported by empirical evidence.