tend to choose friends who share our interests and outlooks, but our
selections may have less conscious and more ancient roots. Recent
research suggests friends share genetic similarities and that resulting
social networks play an important role in human evolution.
In their paper "Friendship and Natural Selection," published in the Proceedings of the National Academy of Science, Nicholas Christakis, a physician and social scientist at Yale, and James Fowler,
a professor of medical genetics and political science at the University
of California at San Diego, write that the number of genetic markers
shared by two friends is about what they would have if they were fourth cousins.
That amounts to about one percent of a human's genetic markers. That doesn't sound like much, but Fowler explains in a Washington Post story
that has huge implications for human evolution. Researchers found the
genes that friends have in common seem to be evolving faster than other
genes, so our social environments and social networks could be a key
no gene for friendship, and no way to predict friendship among people
because of a particular genetic trait. But the genetic data of two
people provides clues to whether they will become friends. The
researchers developed a genetic "friendship score" that suggests the
likelihood of friendship. Individuals don't consciously recognize these
similarities, but they are statistically measurable in huge data sets.
are likely to share genes associated with the sense of smell. Being
drawn to the same scent could attract us to certain environments, the
authors suggest: people who like the smell of coffee might be drawn to
coffee shops where they meet others who like the smell. The authors
think our sense of smell may be one of the mechanisms humans use to
identify genetically similar friends, though they emphasize more
research is needed to discover how that happens.
and Fowler examined genetic information and details of social
relationships documented among nearly 2,000 people who participated in
the Framingham Heart Study
that began in 1948. They and colleagues analyzed nearly 1.5 million
markers of gene variations, and compared the data for pairs of unrelated
friends and pairs of unrelated strangers. Because nearly all the people
in the study had similar European origins, the findings weren't
explainable by the tendency to gravitate to others of similar
friends are less likely to share genes associated with immunity to
specific diseases, the authors note, and that that could be an
evolutionary advantage. We're somewhat less susceptible to the things
that sicken our friends.
In their book Connected,
Christakis and Fowler write that social networks are in our genes.
After studying friendship networks among 1,110 twins drawn from national
health data of 90,115 adolescents, they discovered that social network
structure was influenced by genes: kids located at the center of their
networks had a different genetic makeup than those located at the
periphery, and those whose friends were closely connected had different
genetic make than those with friends in divergent groups.
the new paper they discuss the role of genes in a broader social
environment where we interact and collaborate with friends and
strangers. "Our results support the idea that humans might be seen as metagenomic
not just with respect to the microbes within them, but with respect to
the humans around them. It may be useful to view a person's genetic
landscape as a summation of the genes within the individual and within
the people surrounding the individual, just as in certain other