The research team used data from the National Longitudinal Study of Adolescent Health. Boardman's team focused on 1,503 pairs of friends in seventh through 12th grade in 41 schools. As with the earlier study, Boardman's group found that some pairs of friends shared certain genetic characteristics.
The team tested the evidence, arguing that if genes were the driving friendship factor, genetically based friendship should emerge most often and easily in schools with the least amount of social friction. "But we found the exact opposite," he said.
In the most socially equal environments, genetic homophily (or love of the same) was "pretty weak," meaning that friends were less likely to share genetic traits. He added, "It was in the most unequal social environments that we saw the highest level of genetic homophily."
In a socially stratified school, "Students from different populations within the school may be effectively 'off limits' for friendships," the team wrote.
While applauding the revolutionary advances in genetics in recent years, Boardman said "we have to have social scientists at the table, because we're the ones with the data, methods and theories to characterize the multidimensional and multilevel nature of the social environment."
Scientists cannot fully understand heritable changes in gene expression unless they understand "what kind of schools people go to, what neighborhoods they live in" and other social factors, Boardman said.
"To me, to say whether genes predict friendships without understanding the context within which these friendships may or may not occur just doesn't tell the whole story."
|Contact: Jason Boardman|
University of Colorado at Boulder