A new US study revealed that friends may be genetically linked, explaining the "chemistry" we feel with those closest to us.
Science has explained why you finish off each other's sentences and share the same love of fashion, sauvignon blanc and George Clooney. US researchers have found you and your "BFF" may also share very specific compatible genes, MSNBC reported.
This genetic link may explain the chemistry among friends, said lead author Dr James Fowler, a professor of medical genetics and political science at the University of California, San Diego, whose research focused on social networks, health and the biological basis of behaviour.
According to Dr Fowler, "the whole idea of friendships is very weird," as humans are the only species that form long-term friendships that aren't based on the need to procreate. The genetic link may begin to provide a scientific explanation for this behaviour.
In the study, researchers gathered data from two large studies that asked participants about their friendship ties and social network: the National Longitudinal Study of Adolescent Health, and a replication study in an independent sample collected from the Framingham Heart Study.
Those who carried a particular genetic marker for a gene called DRD2, a dopamine receptor, tend to make friends with other DRD2-positive people. Individuals who lacked the gene tended to form friendships with people who were also DRD2-negative, the researchers said.
But the scientists also found that sometimes, opposites really do attract. Those who carried a version of a gene called CYP2A6 made friends with people who didn't carry it.
"Humans live our lives in social networks in a sea of genes," said co-author Dr Nicholas Christakis, a professor of medicine and sociology at Harvard Medical School.
"And the fact that we're showing that it's not just our own genes, but [also] the genes of other people [having] relevance in our lives, has a lot of implications."
The study was published in PNAS, the journal of the US National Academy of Sciences.