Human Kin Investment as a Function of Genetic Relatedness and Lineage

Two independent samples of students were asked to allocate fictional lotteries of varying dollar amounts to their blood relatives. In both studies, a reliable genetic relatedness by lineage interaction emerged, such that the genetic effect was a more positive predictor of percent of money allocated for relatives of a direct lineage (e.g., parents, grandparents) than it was for peripheral relatives (e.g., siblings, aunts and uncles). In a third study, this interaction was replicated in an archival analysis of wills. The implications of accounting for differences in relatives' lineages in studies of kin investment are discussed