Groups of friends share more DNA than strangers, experts discover
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Unrelated friends share 1% of genes - similar to fourth cousins with the same great-great-great grandparents. Stock image pictured
Even if you think you share everything with your friends, you may have more in common than you suspect.
For new research reveals that groups of pals have a remarkable number of the same genes.
The study, which gives new weight to the saying that 'birds of a feather flock together', found that friends share significantly more DNA than strangers.
Geneticists discovered that unrelated friends have 1 per cent of genes which match - about the same as fourth cousins who share great-great-great grandparents.
The finding means scientists are even able to make a calculated guess as to which people are likely to become friends, just by testing their DNA.
Such a test is more accurate than genetic tools used to predict risk of obesity or schizophrenia.
Professor James Fowler, a medical geneticist at the University of California at San Diego, said: 'Looking across the whole genome, we find that, on average, we are genetically similar to our friends.
'We have more DNA in common with the people we pick as friends than we do with strangers in the same population.'
Professor Nicholas Christakis, a sociology who co-wrote the study, added: 'One per cent may not sound like much to the layperson, but to geneticists it is a significant number.
'We are somehow, among a myriad of possibilities, managing to select as friends the people who resemble our kin.'
The academics, whose research was published in the journal Proceedings of the National Academy of Sciences, suspect tat the tendency to choose friends who are genetically similar is rooted in human evolution.
Early human beings may have formed groups if they were genetically suited to certain environments, or had similar likes and dislikes.
Researchers suspect the tendency to choose genetically similar friends is rooted in evolution. Illustration of DNA pictured. Early humans may have formed groups genetically suited to certain environments. The trait, known as 'functional kinship', may have also been driven because some attributes only work when shared
Those who had a similar susceptibility to the cold, for example, may have helped each other build a fire.
The trait - which the scientists call 'functional kinship' - may have also been driven because some genetic attributes only work if you have someone to share it with.
WHAT IS FUNCTIONAL KINSHIP?
The academics, whose research was published in the journal Proceedings of the National Academy of Sciences, suspect that the tendency to choose friends who are genetically similar to us is rooted in human evolution.
Early human beings may have formed groups if they were genetically suited to certain environments, or had similar likes and dislikes.
Those who had a similar susceptibility to the cold, for example, may have helped each other build a fire.
The trait - which the scientists call 'functional kinship' - may have also been driven because some genetic attributes only work if you have someone to share it with.
The first, most intelligent humans to develop speech would have grouped together with others who had the same skill, they said.
Among the sets of genes they studied, those affecting the sense of smell were among the most similar among friends.
A possible reason is that our sense of smell draws us to similar environments, the scientists suggest.
People who enjoy the smell of coffee, for instance, may be more likely to frequent cafes, providing an opportunity to make friends with others of a similar disposition.
The first, most intelligent humans to develop speech would have grouped together with others who had the same skill, they said.
Professor Fowler said: 'The first mutant to speak needed someone else to speak to.
'The ability is useless if there's no one who shares it. These types of traits in people are a kind of social network effect.'
The scientists analysed the genetic make-up of 1,932 people, finding that those who were friends had significantly more genetic resemblance than those who were strangers.
The authors wrote: 'Humans may - when choosing friends from among individuals who are strictly not related to them - come to choose individuals who resemble them on a genotypic level.'
Among the sets of genes they studied, those affecting the sense of smell were among the most similar among friends.
A possible reason is that our sense of smell draws us to similar environments, the scientists suggest.
People who enjoy the smell of coffee, for instance, may be more likely to frequent cafes, providing an opportunity to make friends with others of a similar disposition.
The opposite was true for genes controlling immunity.
Friends were more likely than strangers to have different genetic defences against various diseases.
The scientists believe it may reflect the evolutionary advantage of connected people withstanding a wide range of infections, thereby reducing the likelihood of epidemics.
They also suspect that those genes which are most shared in friends also seemed to be evolving faster.
This may help to explain why human evolution has sped up over the last 30,000 years, and may have suggest that the phenomenon has played in accelerating human evolution.
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