A 2014 study found that friends could be a kind of "functional kin," sharing certain genotypes with each other to gain an evolutionary benefit. The study examined the genes of almost 2,000 people, comparing friend pairs with stranger pairs, and found that on average, friends had more genes in common than strangers did. Genes that related to the sense of smell were particularly likely to be shared between friends, whereas those related to immunity tended to have less overlap.
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Key Facts In This Video
Your genes may be similar enough to those of your friends that you could pass as fourth cousins. 00:25
Some of the most common genes shared between friends are related to the sense of smell. 01:14
Sniffing someone's body odor could help you to analyze their immune response. 01:59