KIN SELECTION (see Glossary) theory shows how

individuals gain INCLUSIVE FITNESS indirectly through the reproduction of related individuals (INDIRECT FITNESS) as well as directly through their own reproduction (DIRECT FITNESS) [1–3]. By doing so, kin selection theory provides a framework for understanding a wide range of social interactions, including ALTRUISM, cooperation, aggression, selfishness and spite. In its simplest form, Hamilton’s rule states that altruism (or reduced aggression and/or selfishness) is favoured when rb − c>0, where c is the fitness cost to the altruist of an action, b is the fitness benefit to the beneficiary and r is their genetic RELATEDNESS. Kin selection theory has been extremely successful in explaining a variety of phenomena