A model of sex-based social stability

For some time theoretical biologists have been discussing the origin of sexes, which seems somewhat puzzling as there are intrinsic inefficiencies for a species to produce males and females, rather than hermaphrodites. We propose that part of the explanation of this may be the additional social stability that sexes offer. We use notions from cooperative game theory to show that for hermaphrodites, it may be impossible for a social group to find a stable set of partnerships. The existence of such a stable set of partnerships is, however, guaranteed for species with both males and females.