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Add Health Study: Do We Really Pick Our Friends Based on Genetic Similarities?

Using school, network and genetic data from the National Longitudinal Study of Adolescent Health, researchers at the University of Colorado and Yale University studied the effects of social environment and genetic factors on friendship selection, adding to the growing body of research on the role of genetic homophily in friendship formation. Their results suggest that social context plays a fundamental role in friendship formation, as a social environment can facilitate or restrict the opportunity to select friends with similar genotypes.

Using school, network and genetic data from the National Longitudinal Study of Adolescent Health, researchers at the University of Colorado and Yale University studied the effects of social environment and genetic factors on friendship selection, adding to the growing body of research on the role of genetic homophily in friendship formation.  Their results suggest that social context plays a fundamental role in friendship formation, as a social environment can facilitate or restrict the opportunity to select friends with similar genotypes. 

Read the Smithsonian story here:  Do We Really Pick Our Friends Based on Genetic Similarities? (by Joseph Stromberg, released on October 09, 2012). 

Excerpt:  “In recent years, as DNA sequencing has gotten increasingly quicker, cheaper and easier, some researchers have looked at individuals’ genes and come to a surprising finding – that people who are friends are disproportionately likely to share certain similarities in their genetic makeup. 

Some scientists have even hypothesized that this is the result of an evolutionary advantageous strategy, similar to the theory of inclusive fitness for kin: As a prehistoric human, if you tended to stick together and support others with whom you share genes, helping them survive led to the survival of your own genes, even if you personally didn’t make it to pass your genes on to your offspring.  Under that theory, we’re able to recognize our non-family genetic brethren and, consciously or not, become friends with them based on that similarity.

A group of social scientists led by Jason Boardman of the University of Colorado, however, was skeptical.  They doubted whether genetic similarity was really driving the way we pick our friends – and had a suspicion that, instead, other social factors drove us to become friends with people we happen to share genes with.  In order to test their hypothesis, they dove deep into data from the National Longitudinal Study of Adolescent Health, which gathers a wide range of data on thousands of middle- and high-school students across the country, on everything from risk-taking behavior to particular genetic alleles to relationships with others.

Their findings, presented in an article published yesterday in the Proceedings of the National Academy of Sciences, strongly rebut the idea that genes determine friends and instead present an alternate idea: that social mechanisms simply put us into situations where we’re exposed to people we share genes with, and that we become friends with them based on this context.”

Dr. Jason D. Boardman is an associate professor in the Department of Sociology, University of Colorado at Boulder, and research associate in the Population Program at the Institute of Behavioral Science, University of Colorado at Boulder.  Benjamin W. Domingue is a doctoral student in the Population Program at the Institute of Behavioral Science, University of Colorado at Boulder.  Jason M. Fletcher is an associate professor in the Division of Health Policy and Management at Yale School of Public Health, and a scholar in the Robert Wood Johnson Health and Society Scholars Program at Columbia University. 

Scholarly source:  Jason D. Boardman, Ph.D., Benjamin W. Domingue, and Jason M. Fletcher, Ph.D. (2012). How social and genetic factors predict friendship networks. Proceedings of the National Academy of Sciences http://dx.doi.org/10.1073/pnas.1208975109