When it comes to friends versus family, you like to keep each separate. You get to say the most outlandish things to your mates knowing they'll never tell your parents, but when you need people to squabble with over Sunday lunch, you've got your family. That could all be wrong, though, as according to a new study, turns out that we somehow strike up friendships with our semi-distant relatives. On average, close friends are likely to have as much shared ancestry as fourth cousins – people who share great, great, great grandparents.
Scientists found this out when they were doing some studies of 2,000 people in order to find out the factors influencing heart disease. First off, their DNA was analysed to show up any mutations. Then, Professor James Fowler from the University of California and Nicholas Christakis of Yale University took pairs of people – either strangers or friends – and analysed their DNA to work out if they were similar to one another.
The strangers were pretty different to each other, but the mutations in the friends tended to match up: 'Looking across the whole genome we find that, on average, we are genetically similar to our friends,' Professor Fowler said. 'We have more DNA in common with the people we pick as friends than we do with strangers in the same population.'
The friends would have a genetic similarity of one per cent of their DNA, which is actually a lot. 'One per cent may not sound like much to the layperson but to geneticists it is a significant number,' Professor Christakis said.
And it wasn't because the people tended to choose friends of the same ethnic group; the people in the test were overwhelmingly Americans of European ancestry.
Why are we drawn to our relatives when choosing mates? Well, it could be because the mutations we carry need to be carried by whoever we breed with in order to make it to the next generation. 'The first mutant to speak needed someone else to speak to,' Professor Fowler wrote in the journal Proceedings of the National Academy of Sciences, reports The Independent. 'The ability is useless if there's no one who shares it.'
And apparently we are drawn, via smell, to people who are genetically similar to us.
That said, what good is there in being able to sniff out a friend who's related to us if we're all stupid enough not to consciously work out that our friend is our fourth cousin? Should we really be allowed to breed if we're that stupid?
** Follow Sophie on Twitter @sophwilkinson**
Picture: Lukasz Wierzbowski
This article originally appeared on The Debrief.