Abstract
The evolutionary dynamics of social traits depend crucially on the social structure of a population, i.e. who interacts with whom. A large body of work studies the effect of social structure on behaviors such as cooperation, but relatively little is known how the social structure co-evolves with social traits. Here, I present a model of such coevolution, using a simple yet realistic model of within-group social structure. In this model, social connections are either inherited from a parent or made by meeting random individuals. My model shows that while certain conditions on the social structure (low probability of making random connections) can select for cooperation, the presence of cooperation selects against these conditions, leading to the collapse of cooperation. Inherent costs of making social connections unrelated to cooperation can prevent this negative feedback. However, the more beneficial cooperation is, the higher linking costs have to be to counteract the self-limitation. These results illustrate how coevolutionary dynamics can constrain the long-term persistence of cooperation or the aggregate benefits from it.