Friends who are unrelated share a high proportion of similar genes, new research has shown.
On average the one percent of the genes of pairs friends matched each other when compared with pairs of strangers, according to the study published in the journal Proceedings of the National Academy of Sciences.
US lead scientist Professor James Fowler, from the University of California at San Diego, said: "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."
Scientists believe that a possible reason this, is that our sense of smell draws us to similar environments, citing the example of people who enjoy the aroma of coffee 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 so friends were more likely than strangers to have different genetic defences against various diseases.