Humans Choose Friends With Similar DNA

KentuckyFC writes "The study of social networks has long shown that people tend to pick friends who are similar to them — birds of a feather stick together (PDF). Now a study of the genomes of almost 2000 Americans has found that those who are friends also share remarkable genetic similarities. 'Pairs of friends are, on average, as genetically similar to one another as fourth cousins,' the study concludes. By contrast, strangers share few genetic similarities. The result seems to confirm a 30-year-old theory that a person's genes causes them to seek out circumstances that are compatible with their phenotype. If that's the case, then people with similar genes should end up in similar environments and so be more likely to become friends."

Similar areas?

[Anonymous Coward]

Was there a control for geographically similar area? If you live in certain areas like Appalachia, everyone you know is probably a fourth cousin. So of course your friends would be related to you.

Could it be something more basic?

[lagomorpha2]

In a number of different memoirs from actors in the original Planet of the Apes, it was noted that people playing different types of apes always sat with each other at lunch. It was a bizarre granfalloon - baboons with baboons and orangs with orangs for no other reason than that they looked the same. And these were people that knew each other before the film.

People have a natural inclination to like people that look more like them whether it makes sense in modern society or not.

Fourth cousins?

[Tony Isaac]

If there are only six degrees of separation between you and just about everybody on earth, the classification "fourth cousin" probably covers a large part of the earth's population!

Re:2000 Wyoming (or Montana, or Nebraska) citizens

[Bill, Shooter of Bul]

I find your comment to be the same. Assuming that people in the city are more sophisticated than "rednecks who listen to country music and drink cheap beer and whisky"? How is that not an elitist comment? Cultural bubbles can also exist within large urban areas. This is how you end up with a Little Italy, China Town, etc sections in each large city. There are others not so visually apparent, I'm just picking on commonly known ones who's existence I wouldn't have to argue about.

Choice of circumstance?

[fahrbot-bot]

I'm reminded of the Better Off Ted episode Get Happy [tvrage.com]

Linda suggests that Veridian let its employees have decorations in their company. Veronica agrees, but the company selects the decorations and assigns them to the employees. Linda discovers that she's suddenly a cat person, while other employees have cars, Green Bay Packers, or space decorations.

... Linda bonds with her fellow cat employees who start obsessing about cats... At lunch, Linda decides to talk with the outer space employees. They think they're too smart for her, and the cat employees see her as a traitor... Later, Linda discovers that the cat people have destroyed her cat decorations.

"Veridian Dynamics. Teamwork. It keeps our employees gruntled."

Re:Could it be something more basic?

[moteyalpha]

That reflects something that I pondered. In terms of neural networks and the ability to recognize familiar things. The action of recognizing could be a composite of those people you have become familar with. In other words, a person could see someone and assign them for recognition by the similarity of their traits to others that are already impressed on their brain such that they would be 10 percent like my cousin, have a nose like my brother, walk ike my sister, etc. So in the same way that people communicate in the language they learn as a child, they can only recognize based on the visual clues that act as a type of hidden language of form, action, and appearance. People of similar genotypes would naturally have similar recognizable features and people who share culture would have the similar and understandle behavior and speech. I aree with some other poster that everybody shares similar DNA, it just depends on how similar you want to get since some genetic sequences are conserved across a vast range of genotypes / phenotypes and even extend to single cell organisms, I am certain that all organisms share most of the tRNA molecules and rRNA structure. So people like to be in familiar surroundings because it reduces the stress of dealing with unfamiliar environments.

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[account_deleted]

Comment removed based on user account deletion

Re:Bull

[Samantha Wright]

The suspicion that part of social compatibility can be explained through superficial genetic traits has been explored before. The bibliography on page 21 of the totally free and unpaywalled arxiv PDF [arxiv.org] has a few citations that seem pretty similar.

That being said, I'm not so sure about some of their conclusions; they make it sound like there are purely mechanistic reasons why we seek out the friends we do. Consider the following:

The implications of the finding regarding homophily on genes related to linoleic acid metabolism are unclear. Linoleic acid is a precursor for substances involved in a broad range of important bodily processes (ranging from adipocyte function to bone formation to the regulation of gene expression) (42), and the component genes in the pathway are related to the metabolism of cholesterol, steroids, and various ingested substances, though it is intriguing that linoleic acid compounds might be used by moths as pheromones (43). Possibly, this pathway is related to the restrained consumption or the specific metabolism of various foodstuffs, traits for which homophily may be advantageous and heterophily self-injurious.

Personally, I think this is patently absurd and that there is no way this could influence personality or human behaviour. It seems to me to be more likely that the linoleic acid genes either have some wildly obscure indirect effect on personality that we can detect, or that they're simply inherited by chance with something that does.

It would have been wonderful if people here actually bothered to RTFA so we could argue about whether or not biochemically-inclined sociologists are out to destroy civilization by being too narrow-minded. On the plus side, this is a biology paper that was submitted to Arxiv, which means that it probably is having trouble getting into a major journal (i.e. it's very possibly being regarded as crap by journal editors due to its weird conclusions.)

Re:Bull

[interkin3tic]

That doesn't make the findings impossible. The genetic variation is known or could be estimated given the demographics of a person's locale, and you could compare the profile of expected (if friend making was completely random) to actual pretty easily. If they don't match up, then there's some selection going on.

For example, if you're white and live in the bronx, and significantly less than half of your local friends are hispanic [wikipedia.org], then obviously race factors into who you make friends with in some way. You could do the same thing with genetic markers.

Re:How dare you!?

[Stormy Dragon]

Groucho wasn't being self deprecating, he was mocking the anti-semitism of the time and how once he became famous, all these organizations that normally would never have considered letting someone Jewish join suddenly wanted him to become a member.