Friendship and Genetic Similarity By Brian Simpson

It was once common sense, but science is re-discovering that even friends are usually genetically similar, for like goes with like.

https://time.com/5095903/genetic-similarities-friends-study/

“You may have more in common with your friends than you think, according to a new study published in Proceedings of the National Academy of Sciences. Your genes may be similar, too.

Past research has suggested that people tend to be somewhat genetically similar to their spouses and adult friends, likely because humans naturally gravitate toward people with whom they have something in common. But how and why does this subconscious sorting happen? Researchers from Stanford, Duke and the University of Wisconsin—Madison studied 5,000 pairs of adolescent friends using data from Add Health, a long-term study of people who were in grades seven through 12 during the 1994-1995 school year. They ran a number of genetic comparisons, seeking to learn more about pairs of friends and schoolmates.

Overall, the researchers found that friends were more genetically similar than random pairs of people, and about two-thirds as similar as the average married couple. Study author Benjamin Domingue, an assistant professor at the Stanford Graduate School of Education, says this similarity is strong enough to detect, but not nearly on the same level as siblings, for example.

https://www.pnas.org/content/pnas/115/4/702.full.pdf

“Humans tend to form social relationships with others who resemble them. 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. We extend this work by using data from 5,500 adolescents from the National Longitudinal Study of Adolescent to Adult Health (Add Health) to examine genetic similarities among pairs of friends. Although there is some evidence that friends have correlated genotypes, both at the whole-genome level as well as at trait-associated loci (via polygenic scores), further analysis suggests that meso-level forces, such as school assignment, are a principal source of genetic similarity between friends. We also observe apparent social– genetic effects in which polygenic scores of an individual’s friends and schoolmates predict the individual’s own educational attainment. In contrast, an individual’s height is unassociated with the height genetics of peers.”

As I said, this was something commonly known before the manic age of political correctness. Friends are usually part of the racial tribal family.