Collapse and rescue of cooperation in evolving dynamic networks

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 about how social structure itself coevolves with social traits. Here, I use a simple yet realistic model of within-group social structure to study such coevolution. In this model, social connections are either inherited from a parent or made with random individuals. My model shows cooperation can evolve when individuals make few random connections, but the presence of cooperation selects for increased rates of random connections, which leads to the collapse of cooperation. Inherent costs of social connections can prevent this negative feedback, but the more beneficial cooperation is, the higher linking costs have to be maintain it, and linking costs can negate some or all of the aggregate benefits of cooperation. Exogenously maintained social inheritance can mitigate the latter problem and allow cooperation to persist and increase the average fitness of a population. These results illustrate how coevolutionary dynamics can constrain the long-term persistence of cooperation.