early hunting and foraging societies (the EEA for humans) may persist even if they are not adaptive for humans’ current environment. Mechanisms behind parental investment may respond to cues in the modern environment that actually work against genetic fitness. In the past, humans had fewer resources and often lived in close kin networks. The presence of a genetic stranger was unlikely. Now, however, humans’“ innate psychological predispositions that promote an intense desire for children” may “permit the formation of close relationships with infants and children of strangers”. These underlying mechanisms may actually (if accidentally) facilitate adoption. As a result of these evolutionary blunders, adoptive parents may invest as if their children were their own biological sons and daughters.
Evolutionary scholars sometimes use the EEA to explain results contradictory to kin selection theory. Experts suggest that adoption as a practice among unrelated individuals has “neither historical nor evolutionary underpinnings” to account for some archival evidence that adoptive and biological parents bequeathed the same amount to their children. They imply that the current context in which adoption occurs is so new that evolutionary predispositions have not yet caught up, leaving adoptive parents vulnerable to intrinsic desires for children that once served them well. Evolutionary psychologists, however, typically do not apply the EEA to stepfamily research that tends to support kin selection theory. Thus, the EEA appears on a practice-to-practice basis rather than detailing the specific conditions under which it is relevant; this inconsistent use makes it difficult to falsify the theory and limits its explanatory utility. Arguably, today’s stepfamilies (and all family forms in the United States) are influenced by a social context that is new by evolutionary standards—one in which the institution of marriage and a postindustrial world shape family relations. Logically, if applied uniformly, the EEA implies that a love for children influences all parents—not just adoptive ones. Therefore, if the EEA is the main explanatory factor, we would expect no differences in the levels of investment by two-adoptive-parent families, two-biological-parent families, and other alternatively structured families.
