Kin Selection, Fitness and Cultural Evolution
The two major modes of evolutionary change that are not based on differences in individual fitness have been termed group selection and kin selection. This chapter considers kin selection, particularly in human hunting-gathering populations. The kin selection model proposed by W. D. Hamilton for explaining fitness altruism spoke primarily of a single recipient of an altruistic act although Hamilton did not limit the applicability of the model to the situations. The model of kin selection and the usual model of kin selection are unrealistic in opposite directions. Hamilton’s model of inclusive fitness implicitly assumes that kindreds containing altruists grow without density dependent regulation of numbers. Cultural evolution occurs whenever the frequency of particular learned behaviors change within a society. A particular cultural trait or learned behavior may increase in frequency while lowering the Darwinian fitness of carriers. The changes in cultural evolution can be transmitted not only to descendants but can diffuse “laterally” to collateral relatives or to non-relatives.