Adoption and Fosterage in Human Societies: Adaptations or Enigmas?

Abstract

The significance of the role of biological kinship in human social interactions lies at the heart of the contemporary debate over the extent to which natural selection has shaped patterns of human behavior and influenced the structure of human social organization. Some cultural anthropologists contend that there is no relationship between biological relatedness and human kinship systems, and therefore expect to find no systematic association between genetic kinship and patterns of social behavior (e.g., Sahlins 1976; Schneider 1968). At the same time, other anthropologists who have been influenced by contemporary theoretical developments in evolutionary biology, expect kinship' to have a profound impact upon the pattern of human social interactions (e.g., Irons 1979b; Durham 1979). This view derives from the theories of kin selection (Hamilton 1964) and reciprocal altruism (Trivers 1971; Axelrod and Hamilton 1981), which predict that altruistic behaviors, defined in this context as acts that increase the genetic fitness of the recipients at some cost to the donors, will be limited to close kin or reciprocating partners.2 In his influential critique of human sociobiology, Sahlins (1976) cites adoption as compelling evidence that biological kinship plays a relatively unimportant role in the patterning of human social relationships. In Oceania, the North American Arctic, and West Africa a substantial fraction of children grow up outside their natal households (Carroll 1970; Brady 1976; Guemple 1979; Goody 1982). In their adoptive or foster3 households they are nurtured, fed, clothed, housed, socialized, and educated. Adoption, which seems to involve unreciprocated altruism on behalf of genetically unrelated children, apparently violates the predictions of contemporary evolutionary theory (Sahlins 1976). However, the existence of institutions like adoption and fosterage does not necessarily negate the importance of biological kinship relationships (Alexander 1979; Silk 1980). In Oceania, for example, adoption occurs primarily among close kin, natural parents retain an active interest in their children's welfare after adoption, and competition occurs among natal and adoptive siblings over the dis-