David Friedman claims that it’s not just the religious right that rejects evolution but the left as well, because it refuses to accept the importance of heredity. In Nature vs Nurture: A Natural Experiment, he discusses a study that addresses some age-old questions:
From 1970-1980, a large number of Korean-American children were placed for adoption by an agency which assigned them at random to adoptive families. That meant that any correlation between characteristics of the families, such as maternal education, socio-economic status, or income, and characteristics of the children as adults, would be due to environment not genetics. By comparing the strength of the relation between characteristics of parents and adoptive children with the corresponding figure for parents and biological children raised by those parents, one can get at least some estimate of how much of the relation comes from which cause.The conclusion is striking. An increase of one year in maternal education produces an increase of only .07 years in the education of an adoptive child but an effect four times as large on the education of a biological child. Similar results apply to a variety of other characteristics. It looks as though being brought up by well off or well education parents is indeed an advantage, but a considerably smaller advantage than being the biological child of such parents.