How hungry is the selfish gene?

We examine resource allocation in step-households in the United States and South Africa to test whether child investments vary according to economic and genetic bonds between parent and child. In the United States, households spend less on food when a child is raised by a nonbiological mother. The reduction is identical for step, adoptive, and foster households, consistent with the hypothesis that genetic ties are the ones that binds. In South Africa, where food spending can be disaggregated, households spend less on milk, fruit and vegetables, and more on tobacco and alcohol, in the absence of a child's birth mother.