Kin selection is a theory to explain why living things engage in behaviors that contribute to the survival and reproduction of others, often at the expense of their own survival and reproduction. In biology, such behaviors are considered examples of altruism (see Altruism ). Kin selection proposes that altruism evolved (developed over time) because altruistic behaviors benefit close relatives of the altruistic individual. Such relatives share many of the same genes, the basic units of inheritance (see Heredity ). Thus, by helping a relative survive and reproduce, the altruistic individual promotes the survival of his or her own genes.
An example of kin selection can be seen in honey bees. A worker honey bee collects nectar that sustains the queen bee and her offspring. The worker’s behavior is clearly altruistic, because it benefits the queen and her offspring at the worker’s expense. Yet, worker bees are also offspring of the queen and share genes with her and her offspring. By helping the queen and her offspring survive and reproduce, worker bees thus help to spread their own genes.
Kin selection was described formally in the 1960’s by the British biologist William D. Hamilton. Hamilton developed a mathematical formula that became known as Hamilton’s rule. It describes conditions under which genes that promote altruism can spread throughout a group.
Hamilton’s theory of kin selection showed how altruism could develop and survive in nature. For this reason, it was celebrated as a major advance in the study of evolution, in part because it seemed to provide an alternative to a controversial theory known as group selection (see Group selection ). Many scientists now regard the two theories as different ways of viewing the same evolutionary process.
See also Hamilton, William Donald .
