Kin Selection Theory - Hamilton (1963)

Equation of altruism

Altruism is favored when... rB - C > 0 R = genetic similarity between altruist + recipient B = fitness benefit to recipient C = fitness cost to altruist

Objective of theory

Proposed this theory to support the following predicament: we are more likely to sacrifice ourselves for relatives than non-relatives and that the degree of altruism can be measured by the number of genes shared by individuals. This is because by sacrificing yourself you can contribute to the survival of your genes (they can carry on surviving) [genetic fitness]

Influenced by Darwin

This theory provides an evolutionary explanation of prosocial behavior; proposes that prosocial behavior - its presence - can be explained by indirect or inclusive fitness. Direct fitness = individual survival and fitness Indirect fitness = (an individual's impact on) the survival and reproduction of relatives Inclusive fitness: equivalent to an individual's total fitness; indirect + direct.

Kin Selection Theory Definition

When an animal engages in 'self-sacrificial behavior' that benefits the genetic fitness of its relatives