Evolution of shame as an adaptation to social punishment and its contribution to social cohesiveness

Feelings of shame are common among humans although shameless individuals do not seem to be handicapped in achieving social success in life. What then is the adaptive value of shame? How can shame have evolved? Here I simulate shame as the emotion that induces an increase in pro‐social behavior after receiving social punishment. Simulations with the agent‐based model, Sociodynamica, show that shame is evolutionary stable in a context of individual selection, without the need for including group selection as an evolutionary force. The adaptive advantage of shame is based on the fact that it increases flexibility to the shameful individual, allowing it to act selfish if the probabilities of being punished are low and achieving a reduction in the costs of social punishment when frequent punishment is likely. The results show that shame, together with pro‐social punishment and social cooperation, produce a fluctuating dynamics of social cooperation, achieving long periods where the populations stabilizes pro‐social behavior interspersed with periods where selfish behavior predominates. This temporal stabilization of pro‐social behavior might provide societies with sufficient time to build institutions that might stabilize sustainable pro‐social behavior. © 2008 Wiley Periodicals, Inc. Complexity, 2008