How Altruism Can Prevail in an Evolutionary Environment

Abstract: We study environments in which an individual gets a higher payoff from defecting than from cooperating and where "copies" of an individual are more likely to appear the higher is the individual's payoff. We demonstrate that even in single-shot prisoner's dilemma models (where cooperation benefits one's opponent at a cost to oneself), evolution can sustain cooperative behavior between relatives or neighbors. In addition, we show that selfish individuals who conciously choose their actions may find it in their interest to be altruistic when there is some probability that their practices will be imitated. Both genetic and cultural inheritance appear to be blunt instruments that do not operate on individuals in isolation. Those who inherit a genetic tendency to cooperate are more likely than others to enjoy the benefits of cooperative siblings. Similarly with culturel inheritance; altruism can prevail when individuals are likely to interact with others who share the same role model.