Tinbergen Institute Discussion Paper No. TI 2020-063/I
Most of the literature on the evolution of human pro-sociality looks at reasons why evolution made us not play the Nash equilibrium in prisoners’ dilemmas or public goods games. We suggest that in order to understand human morality, and human prosocial behaviour, we should look at reasons why evolution made us not play the subgame perfect Nash equilibrium in sequential games, such as the ultimatum game and the trust game. The “rationally irrational” behavior that can evolve in those games is a better match with actual human behaviour, including ingredients of morality such as honesty, responsibility, and sincerity, and also less nice properties, such as anger, as well as the incidence of conflict. Moreover, it can not only explain why humans have evolved to know wrong from right, but also why other animals, with similar population structures and similar rates of repetition, have not evolved the morality that humans have.