Effects of Migration as Environmental Response on the Evolution of Cooperation

Altruistic behaviors are common in humans and some other animals, and are essential in the formation of societies. However, the evolution of cooperation is paradoxical, since altruistic traits confers a cost to the actor and a benefit to other individuals and thus natural selection should favor selfish individuals. Evolutionary biologists have developed theoretical frameworks to explain this paradox. One explanation is reciprocal altruism and another one is kin selection. In 1998, Sober and Wilson proposed a modern version of group selection called “multilevel selection”[2]. This idea has attracted great attention because it could incorporate previous various theories for the evolution of cooperation. Consider a population that is subdivided into groups. An individual in a group including many cooperators gets a higher payoff than in a group including many defectors (between-group selection). A defector gets a higher payoff than a cooperator within the group (within-group selection). Multilevel selection theory shows cooperators evolve when the former selection predominates over the latter selection. Here, one of the most important factors is whether the bias between groups continually exists. In other words, the evolution of cooperation requires a structured population in which cooperators interact