Social evolution is a subdiscipline of evolutionary biology that is concerned with social behaviors that have fitness consequences for individuals other than the actor. Social behaviors can be categorized according to the fitness consequences they entail for the actor and recipient. * Mutually beneficial – a behavior that increases the direct fitness of both the actor and the recipient * Selfish – a behavior that increases the direct fitness of the actor, but the recipient suffers a loss * Altruistic – a behavior that increases the direct fitness of the recipient, but the actor suffers a loss * Spiteful – a behavior that decreases the direct fitness of both the actor and the recipient This classification was proposed by W. D. Hamilton, arguing that natural selection favors mutually beneficial or selfish behaviors. Hamilton's insight was to show how kin selection could explain altruism and spite. Social evolution is also often...