Plastic and Immobile: Unequal Intergenerational Transmission by Genotype within Sibling Pairs

Contrary to traditional biological arguments, the differential susceptibility model suggests genotype may moderate rather than mediate parent-child economic similarity. Using family fixed effects models of Add Health sibling data, I investigate the relationship between an index of sensitive genotypes and intergenerational mobility. Full, same sex sibling comparisons hold constant parental characteristics and address the non-random distribution of genotype that reduces internal validity in nationally representative samples. Across multiple measures of young adult financial standing, those with more copies of sensitive genotypes achieve lower economic outcomes than their sibling if they are from a low income context but fare better from a high income context. This genetic sensitivity to parental income entails lower intergenerational mobility. Results support the differential susceptibility model and contradict simplistic genetic explanations for intergenerational inequality, suggesting sensitive genotypes are not inherently positive or negative but rather increase dependence on parental income and reduce mobility.