Genetic and educational assortative mating among US adults

Abstract

Understanding the social and biological mechanisms that lead to homogamy (similar individuals marrying one another) has been a long-standing issue across many fields of scientific inquiry. Using a nationally representative sample of non-Hispanic white US adults from the Health and Retirement Study and information from 1.7 million single-nucleotide polymorphisms, we compare genetic similarity among married couples to noncoupled pairs in the population. We provide evidence for genetic assortative mating in this population but the strength of this association is substantially smaller than the strength of educational assortative mating in the same sample. Furthermore, genetic similarity explains at most 10% of the assortative mating by education levels. Results are replicated using comparable data from the Framingham Heart Study.

Keywords: genetic homogamy; homophily; random mating.

Fig. 1.

Graphical representation of GAM and EAM. The y axis charts quantiles of the distribution of kinship or squared educational differences between all pairs. The x axis charts quantiles of the same distribution but restricted to just cross-sex white spousal pairs. The shaded area in each gives an estimate of assortative mating. The horizontal and vertical lines aid in interpretation. In Upper Left, one can observe that the genetic relatedness estimate at the 0.5 quantile of spousal pairs corresponds to the 0.55 quantile of all pairs. Adjusted GAM (Lower Left) includes control for same birth region (census division). Adjusted EAM (Lower Right) includes a control for kinship between the pairs.