A recent U.S. study has uncovered something remarkable: the people we choose as friends tend to be genetically more alike to us than random strangers. The research was led by Nicholas Christakis, a Greek-American professor holding dual appointments in sociology and medicine at Yale University, alongside James Fowler, a professor of medical genetics and political science at the University of California.
Their findings were published in the prestigious Proceedings of the National Academy of Sciences (PNAS). To reach their conclusions, the team examined the genomes of 1,932 individuals, carefully comparing genetic pairings between friends and between strangers.
None of the participants shared any blood relation — the only variable at play was the nature of their social bonds.
The data revealed that, on the whole, each participant shared more genetic markers with their friends than with unfamiliar people. The researchers were quick to point out, however, that part of this pattern likely reflects the natural tendency to gravitate toward others who share similar ethnic — and therefore genetic — backgrounds.
Beyond this baseline, the genetic overlap between friends proved even stronger than what would be expected between individuals drawn from the same national and ancestral gene pool. The precise mechanism behind this phenomenon remains unknown.
So just how alike are we to our pals?
According to the findings, the typical friend shares roughly the same degree of genetic relatedness as a fourth cousin — meaning about 1% of our genes are shared with our friends.
Christakis and Fowler went a step further, crafting a "friendship score" capable of forecasting who would become friends with an accuracy rivaling genetic predictions for conditions like obesity or schizophrenia.
Zooming in on specific genes, the study found that friends are more inclined to share DNA linked to the sense of smell, while differing notably in genes governing immune response. This means friends often have varying genetic defenses against illness.
Researchers believe this could be an evolutionary adaptation benefiting society as a whole. By surrounding ourselves with people whose immune systems differ from our own, we may inadvertently create a buffer that slows the spread of infectious outbreaks. Equally fascinating is the observation that genes shared among friends appear to evolve at a faster pace than others.
Professor Christakis suggests this might help explain why human evolution appears to have sped up over the past 30,000 years. He argues that our highly social environment — especially the central role of language — acts as a powerful driver of evolutionary change.
Adding to this, the Greek-American scholar notes that
Anna LeMind, Learning Mind;
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