MONDAY, Jan. 17 (HealthDay News) -- Your friends aren't just people you enjoy: You tend to befriend others with similar or complementary genes, a new study suggests.
Researchers from the University of California, San Diego found that gene clusters were comparable among friends, even after accounting for the predisposition to befriend others in the same geographic area.
The team analyzed two independent U.S. health studies, the Framingham Heart Study Social Network and the National Longitudinal Study of Adolescent Health, which allowed respondents to name friends over a period of time ranging from six to 32 years.
"It does blur the line between nature and nurture, that's for sure," said study author James Fowler, a professor of medical genetics and political science. "We show in this paper that our environments, in part, are based on the genes of our friends. What the study brings to light is that genes of other people are part of what affects our environment."
Mapping specific genetic markers within each individual's social network, the researchers learned that individuals tend to forge friendships with those who share two of six tested markers.
For example, those who carried the so-called DRD2 marker, which is associated with alcoholism, were apt to befriend other DRD2-positive friends, while those without the gene formed alliances with other DRD2-negative peers.
Fowler said this situation exemplifies homophily, a sociological term that means "love of like" and illustrates the adage "birds of a feather flock together."
"We were wondering if this was true not just socially, but biologically and genetically," he said. "It makes sense because we know there are some genes associated with social outcome."
The team was surprised to find that individuals also tend to befriend those with opposite but complementary traits. People who carried a gene kno
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