Why Do People Become Friends?

It's said that friends are the family you choose, and a 2014 study by researchers from Yale University and the University of California at San Diego found that there is more truth to that statement than you might think. The research, which studied an ethnically homogeneous group of individuals, found that people unknowingly choose close friends who have DNA sequences in common. An analysis of 1.5 million markers of gene variations found that pairs of friends tend to have the same level of genetic relation as people do with their fourth cousins, or a great-great-great grandfather.

We're just like family:

• The researchers wanted "to provide a deep evolutionary account of the origins and significance of friendship," said Nicholas Christakis, professor of sociology, evolutionary biology and medicine at Yale.
• The most common gene shared by friends, the study found, was the "olfactory" gene, which is involved in a person's sense of smell.
• On average, pairs of close friends shared 1% of their genes. This might not seem like a lot, but the scientists found it to be significant.