I recently wrote about research which found that people choose spouses with similar DNA.
Now, though, this finding has been generalised to include people who are friends rather than spouses.
The study, published in the Proceedings of the National Academy of Sciences, examined almost 1.5 million markers of genetic variation across almost 2,000 people (Christakis & Fowler, 2014).
From this pool of people they then compared pairs of people who were friends with pairs who were strangers.
It turns out that we’re about as genetically related to our friends as our fourth cousins.
One of the study’s authors, Professor Nicholas Christakis of Yale University, said:
“One percent may not sound like much to the layperson, but to geneticists it is a significant number.
And how remarkable: Most people don’t even know who their fourth cousins are!
Yet we are somehow, among a myriad of possibilities, managing to select as friends the people who resemble our kin.”
Oddly enough, the genes that are most likely to be similar are those which control the sense of smell.
One of the most striking findings of the study, though, is that genes which were more similar between friends are also evolving at the fastest rate.
“The paper also lends support to the view of human beings as ‘metagenomic’, not only with respect to the microbes within us but also to the people who surround us.
It seems that our fitness depends not only on our own genetic constitutions, but also on the genetic constitutions of our friends.”
The authors suggest that the social environment itself may be an evolutionary force which has increased genetic changes over the past 30,000 years.
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Image credit: DG EMPL