Though not biologically related, friends are as "related" as fourth cousins, sharing about 1% of genes. That is【B1】______a study, published from the University of California and Yale University in the Proceedings of the National Academy of Sciences, has【B2】______. The study is a genome-wide analysis conducted【B3】______1,932 unique subjects which【B4】______pairs of unrelated friends and unrelated strangers. The same people were used in both【B5】______. While 1% may seem【B6】______, it is not so to a geneticist. As James Fowler, professor of medical genetics at UC San Diego, says, "Most people do not even【B7】______their fourth cousins but somehow manage to select as friends the people who【B8】______our kin." The study【B9】______found that the genes for smell were something shared in friends but not genes for immunity. Why this similarity exists in smell genes is difficult to explain, for now.【B10】______, as the team suggests, it draws us to similar environments but there is more【B11】______it. There could be many mechanisms working together that【B12】______us in choosing genetically similar friends【B13】______"functional kinship" of being friends with【B14】______! One of the remarkable findings of the study was that the similar genes seem to be evolving【B15】______than other genes. Studying this could help【B16】______why human evolution picked pace in the last 30,000 years, with social environment being a major【B17】______factor. The findings do not simply corroborate people’ s【B18】______to befriend those of similar【B19】______backgrounds, say the researchers. Though all the subjects were drawn from a population of European extraction, care was taken to【B20】______that all subjects, friends and strangers, were taken from the same population. 【B15】