Similar genes promote friendship

People unconsciously choose friends for genetic similarities

Clustering of genotypes in social networks © Fowler et al. / PNAS
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Our genetic make-up not only plays a role in mate choice, but also subconsciously when choosing our friendships. American researchers have discovered that certain genetic markers are piling up within social networks - across geographical distances or across social strata. Obviously, as we report in the "Proceedings of the National Academy of Science" (PNAS), we unconsciously choose people that are similar to us, at least in some genetic traits.


"Same and like to join" - this motto applies not only to many relationships, but also for friendships. That we humans tend to surround ourselves with others that have similar qualities is nothing new. Whether this similarity could also refer to genetic similarities, was so far unclear. It was only known that the genes of people within a region or a social stratum show stronger matches than the average of the population.

Occurrence of genetic markers in social networks

James Fowler of the University of California at San Diego has now explored the relationship between genes and friendship with researchers from Harvard University. As a base, they used data from two independent studies, the National Longitudinal Study of Adolescent Health and the Framingham Heart Study.

In both studies, in addition to the health and genetic parameters of the subjects, their social network was also examined. Each of the participants was therefore asked to name ten or two close friends. In this data, the researchers looked for six specific gene markers and analyzed whether they frequently appeared within the social networks of the subjects. display

Accumulation of similar genes among friends

In fact, it appears that humans tend to gather around others who have at least two of the six gene markers in common with them. This trend was still visible when the scientists calculated the effect of geographical proximity and the same social stratum.

"The results indicate that there is an accumulation of genotypes in social networks that goes well beyond those generated by population stratification, " the researchers explain in their article. "Friends seem to have not only similar properties, but are actually similar at the genetic level, even at the level of specific alleles and nucleotides." Thus, genes shape our environment even more than previously thought and could also on ours Behavior has a significant impact.

For example, one of the examined gene markers, DRD2, is considered to be associated with a predisposition to alcoholism. Interestingly, it has now become apparent that people with this marker tend to have an above-average number of DRD2-positive people around them. However, subjects without this marker had more friendships with other non-carriers of this marker. Since these patterns can also influence the outcome of genetic association studies, these effects should be taken into account, the researchers say.

"An important conclusion of these findings is that the genetic structure in human populations is not only characterized by the formation of reproductive units, but also by the formation of friendships within a population, " the researchers said.

(PNAS, 19.01.2011 - NPO)