Stepchildren are abused, neglected and murdered at higher rates than those who live with two genetically related parents. Daly and Wilson used kin selection theory to explain this finding and labeled the phenomenon "discriminative parental solicitude." I examined discriminative parental solicitude in American households composed of both genetic and unrelated adopted children. In these families, kin selection predicts parents should favor their genetic children over adoptees. Rather than looking at cases of abuse, neglect, homicide and other antisocial behavior, I focused on the positive investments parents made in their children as well as the outcomes of each child. The results show that parents invested more in adopted children than in genetically related ones, especially in educational and personal areas. At the same time, adoptees experienced more negative outcomes. They were more likely to have been arrested, to have been on public assistance and to require treatment for drug, alcohol or mental health issues. They also completed fewer years of schooling and were more likely to divorce. In adoptive families, it appears that "the squeaky wheel gets the grease." Parents invest more in adoptees not because they favor them, but because they are more likely than genetic children to need the help. I conclude that discriminative parental solicitude differs in adoptive and step households because adoptive families generally result from prolonged parenting effort, not mating effort like stepfamilies.
What's going on? In Western countries adoptive parents are screened. Many of them are of higher socioeconomic status, and they adopt children from the general population, with a likely skew toward lower socioeconomic status biological parents. The traits which determine your social status are a combination of environment and genes, the latter mediated through various personality dispositions and attributes. In fact there is plenty of data to show that shared parental environmenthas a marginal long term effect. This is not to say that there aren't environmental inputs which matter, and which adoptive parents bring to the table, but their direct guiding is not the operative element. In The Nurture Assumption Judith Rich Harris puts forward the hypothesis that the unaccounted for environment are peer groups. Does this mean that adoptive parents are in a futile race against genes? No. Genes express themselves in an environment, and that environment is to some extent within the power of a parent to control. That being said the biological parent confers upon the child more than simply superficial physical attributes, or deep aspects of physiology. Rather one's character is partially heritable, and that character is a critical variable in long term life outcomes. As for the title, it's perhaps crassly reductive, and no doubt simplifies the experience of being a parent. At least for many people.