inclusive fitness The adaptive value (fitness) of an individual, taking account not only of that individual's own success, but also of the success of all its kin (i.e. those bearing some portion of the same genotype). J. B. S. Haldane is reputed to have said that he would lay down his life for more than two brothers or sisters, eight cousins, 32 second cousins, etc., these numbers corresponding to the proportions of his own genes shared by these relatives. See also KIN SELECTION.

inclusive fitness The adaptive value (fitness) of an individual, taking account not only of that individual's own success, but also of the success of all its kin (i.e. those bearing some portion of the same genotype). J. B. S. Haldane is reputed to have said that he would lay down his life for more than two brothers or sisters, eight cousins, 32 second cousins, etc., these numbers corresponding to the proportions of his own genes shared by these relatives. See also kin selection.

inclusive fitness The quality that organisms attempt (unconsciously) to maximize as the result of natural selection acting on genes that are influential in controlling their behaviour and physiology. It includes the individual's own reproductive success (usually taken as the number of its offspring that survive to adulthood) and also the effects of the individual's actions on the reproductive success of its relatives, because relatives have a higher probability of sharing some identical genes with the individual than do other members of the population. When interactions between relatives are likely to occur (which happens during the lives of many animals and plants) kin selection will operate.