Friends are family and you choose them because they share many common genes with you.
According to an interesting study, people choose friends who have some DNA sequences in common with them.
"Humans are unique in that we create long term connections with people of our species. Why do we do that? Why do we make friends? Not only that, we prefer the company of people we resemble," said Nicholas Christakis, a social scientist at Yale University in Connecticut.
To reach this conclusion, researchers compared gene variations between 2,000 people who were not biologically related.
After analysing almost 1.5 million markers of gene variations, they found that pairs of friends had the same level of genetic relation as people did with a fourth cousin - or a great-great-great grandfather - that translates to about one percent of the human genome.
"Most people do not know who their fourth cousins are, yet we are somehow, among a myriad of possibilities, managing to select as friends the people who resemble our kin," Christakis contended.
The most common gene shared by friends was the "olfactory" gene - involved in the sense of smell.
The results suggest that choosing friends who share similar genes is a behaviour that may have contributed to human evolution.
The study appeared in the journal Proceedings of the National Academy of Sciences.
