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. We used 18 years of data from the Panel Study of Income Dynamics, and compare food expenditure by family type, holding constant household size, age composition and income. We find that in those households in which a child is raised by an adoptive, step or foster mother, less is spent on food. We cannot reject the hypothesis that the effect of replacing a biological child with a non- biological child is the same, whether the non-biological child is an adoptive, step or foster child of the mother. In South Africa, where we can disaggregate food consumption more finely, we find that when a child's biological mother is the head or spouse of the head of household, the household spends significantly more on food, in particular on milk and fruit and vegetables, and significantly less on tobacco and alcohol. The genetic tie to the child, and not any anticipated future economic tie, appears to be the tie that binds.