Though not biologically related, friends are as "related" as fourth cousins, sharing about 1% of genes. That is（1）_____a study published from the University of California and Yale University in the Proceedings of the National Academy of Sciences, has（2）_____.

The study is a genome-wide analysis conducted（3）_____1932 unique subjects which（4）_____pairs of unrelated friends and unrelated strangers. The same people were used in both（5）_____.

While 1% may seem（6）_____,it is not so to a geneticist. As co-author of the study James Fowler, professor of medical genetics at UC San Diego says, "Most people do not even（7）_____their fourth cousins but somehow manage to select as friends the people who（8）_____our kin."

The team also developed a "friendship score" which can predict who will be your friend based on their genes.

The study（9）_____found that the genes for smell were something shared in friends but not genes for immunity. Why this similarity in olfactory genes is difficult to explain, for now. （10）_____, as the team suggests, it draws us to similar environments but there is more（11）_____it. There could be many mechanisms working in tandem that（12）_____ us in choosing genetically similar friends （13）_____than "functional kinship" of being friends with（14）_____!

One of the remarkable findings of the study was that the similar genes seem to be evolving（15）_____than other genes. Studying this could help（16）_____why human evolution picked pace in the last 30,000 years, with social environment being a major（17）_____factor.

The findings do not simply corroborate people's（18）_____to befriend those of similar（19）_____backgrounds, say the researchers. Though all the subjects were drawn from a population of European extraction, care was taken to（20）_____that all subjects, friends and strangers were taken from the same population. The team also controlled the data to check ancestry of subjects.