Adult sex friend
We considered the genetics of three phenotypes: height, body mass index (BMI) (a measure of adiposity), and educational attainment.We used polygenic scores to summarize phenotype-related genetics.Add Health surveyed 90,118 US adolescents aged 12–18 in 1994–1995 using a school-based sampling frame.
We linked these genetic data with social network information from the original school-based surveys along with information about personal characteristics and social environments accumulated across Add Health follow-up waves.Whether this sorting of like with like arises from historical patterns of migration, meso-level social structures in modern society, or individual-level selection of similar peers remains unsettled.Recent research has evaluated the possibility that unobserved genotypes may play an important role in the creation of homophilous relationships.Among non-Hispanic whites in Add Health, KING estimates of genetic homophily were about two-thirds the magnitude of our previous KING estimates of genetic similarity among spouses in the US Health and Retirement Study (friend similarity = 0.031, CI = 0.022–0.036, compared with spousal similarity = 0.045 from ref. REAP estimates of genetic similarity were somewhat smaller.
Our second analysis tested whether friends were more similar to one another on specific phenotype-related genetic dimensions.
Adult friends are, on average, more genetically similar than random pairs from the population (13).