Social evolution as viewed as a set of behaviours that are "social" and have fitness consequences for both the individual that performs the behaviour (the actor), and another individual (the recipient). Social behaviours can be categorized according to the fitness consequences they entail for the actor and recipient. A behaviour that increases the direct fitness of the actor is mutually beneficial if the recipient also benefits, and selfish if the recipient suffers a loss. A behaviour that reduces the fitness of the actor is altruistic if the recipient benefits, and spiteful if the recipient suffers a loss.

This classification was proposed by W. D. Hamilton. It is easy to see how natural selection favours mutually beneficial or selfish behaviours. Hamilton's insight was to show how kin selection could explain altruism and spite.

See also

• Sociocultural evolution

Theories of history