The Evolution of Moral Codes of Behavior

Within a standard stochastic evolutionary framework, we study the evolution of morality, both at the level of behavior and at the level of codes of behavior. These moral codes involve sanctioning deviant agents. We provide conditions under which the presence of inter- roup conflict allows the emergence of moral codes which improve social efficiency. The result depends on both the efficacy of the available sanctioning technology and on the ratio of the number of societies and the number of members which societies are composed of. We also consider the possibility that a moral code involves rewards rather than sanctions. We show that, in contrast with sanctioning moral codes, no system of rewards will evolve and therefore social efficiency cannot be improved via this mechanism.