We May Choose Our Friends Based On Shared Genetics

Senior Contributor
07.16.14 6 Comments
Then how do you explain this, SCIENCE?!

Via Flickr/heart-felt-robot

Then how do you explain this, SCIENCE?!

Here’s an odd question: How do you choose your friends? Shared interests? Physical proximity? Possession of video games or, as high school wears on, illicit substances? According to a new study, none of the above! Your friends are your friends because of your genetics!

Or, at least, that’s the outcome of a study conducted by James Fowler and Nicholas A. Christakis. Specifically:

Across the whole genome, friends’ genotypes at the single nucleotide polymorphism level tend to be positively correlated (homophilic). In fact, the increase in similarity relative to strangers is at the level of fourth cousins. However, certain genotypes are also negatively correlated (heterophilic) in friends. And the degree of correlation in genotypes can be used to create a “friendship score” that predicts the existence of friendship ties in a hold-out sample.

If the names sound familiar, it’s because they’ve ridden the phrase “social networking” to pop science success. Fowler and Christakis have claimed that whether or not you vote is encoded in your genetics, that being obese is “contagious”, and a whole bunch of other claims that, while interesting, are packaged more for sensationalism than accuracy.

And there are a few weasel words in there. If you’re fourth cousins with someone, for example, that means your genetic link goes back four generations: A lot can happen, genetically, in roughly sixty to a hundred years. Look, we don’t know what your family was like. There are 32-year-old grandmas out there.

Also of note is the fact that we tend to make friends based on physical proximity, and populations in many areas tend to be relatively close to each other genetically for obvious reasons. Fowler and Christakis claim it’s more a structural point across the genome than a specific set of genes. That said, none of the friends they studied are actually related to each other, so that does raise a few questions.

This won’t settle the debate between nature and nurture, but it will make it more interesting. And it also gives us an excuse to post adorable photos, so we’re running with it.

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