"Nature teaches beasts to know their friends," wrote Shakespeare. In humans, nature may be less than half of the story, a team led by University of Colorado Boulder researchers has found.
In the first study of its kind, the team found that genetic similarities may help to explain why human birds of a feather flock together, but the full story of why people become friends "is contingent upon the social environment in which individuals interact with one another," the researchers write.
People are more likely to befriend genetically similar people when their environment is stratified, when disparate groups are discouraged from interacting, the study found. When environments were more egalitarian, friends were less likely to share certain genes.
Scientists debate the extent to which genetics or environmental factors -- "nature" or "nurture" -- predict certain behaviors, said Jason Boardman, associate professor of sociology and faculty research associate with the Population Program in CU-Boulder's Institute of Behavioral Science. "For all the social demographic outcomes we care about, whether it's fertility, marriage, migration, health, it's never nature or nurture.
"It's always nature and nurture," he said. "And most of the time it has a lot more to do with nurture."
Boardman's team included Benjamin Domingue, research associate in the Population Program at IBS; and Jason Fletcher, associate professor of health policy at the Yale School of Public Health. Their research was recently published in the Proceedings of the National Academy of Sciences