Neither nature nor nurture: Using extended pedigree data to understand indirect genetic effects on offspring educational outcomes

Families transmit genes and environments across generations. When parents’ genetics affect their children’s environments, these two modes of inheritance can become linked in an “indirect genetic effect.” Such indirect genetic effects may, through bias, account for up to half of the estimated genetic variance in educational attainment. We tested if indirect genetic effects on educational attainment reflect within-nuclear-family transmission (“genetic nurture”) or instead a multi-generational process of social stratification (“dynastic effects”). We analyzed indirect genetic effects on children’s academic achievement in their 5th-9th years of schooling in N=37,117 parent-offspring trios in the Norwegian Mother, Father, and Child Cohort Study (MoBa). We used analysis of pairs of genetically-related families (parents were siblings, children were cousins; N=10,913) to distinguish within-nuclear-family genetic-nurture effects from dynastic effects shared by cousins in different nuclear families. We found that indirect genetic effects on children’s educational achievement were explained primarily by dynastic effects.