Science shows that you and your best friends probably have similar genes

Best friends tend to have a lot in common. Hobbies. Interests. Personalities. Why else would they spend so much time together? But did you know that the characteristics besties share can go even deeper? Yup. It turns out you and your BFFs may actually share some of the same genes.

Researchers from Stanford, Duke and the University of Wisconsin—Madison studied why and how we select our friends. They used data from the long-term Add Health study. In order to learn about the connection between friends and schoolmates, they compared the genes of 5,000 pairs of teenage friends over the course of a school year, and found some striking patterns.

In The Genes

So why do we choose the friends that we do? Researchers discovered that the deciding factor could be linked to genetics. They found that friends tended to have more genetic similarities than mere classmates, and often shared characteristics such as intelligence and body mass index.

But on top of this, life clusters were another contributing factor. Life clusters refer to groups of people brought together by circumstances, such as schools, churches, athletic programs and more. So while classmates were about half as genetically similar as friends, they were also significantly more genetically similar than unaffiliated individuals.

Researchers say this provides further proof of how close genetics and social circumstances are.

Going Deeper

A few questions still remain. “Are individuals actively selecting to be around people who are like them, or is it due to impersonal forces, such as social structures, that we all are affected by?” asked study author Benjamin Domingue, an assistant professor at the Stanford Graduate School of Education. “Our evidence, with respect to friends, suggest that it’s largely the effect of social structures,” he told Time.

The research also suggests that two friends are more genetically similar than two strangers as a result of “social homophily.” This means that people connect based on matching personalities. Essentially, people are subconsciously attracted to others who have shared traits. Those shared traits result from genes.

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. The genetic similarity is noticeable, but not nearly as close as siblings.

So the next time you say “love you like a sister” or describe a best bud as a “brother from another mother,” remember: You’re not that far off.