What’s the genetic ancestry of average Americans?

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In the United States, almost no one can trace their ancestry back to just one place. And for many, the past may hold some surprises, according to a new study. Researchers have found that a significant percentage of African-Americans, European Americans, and Latinos carry ancestry from outside their self-identified ethnicity. The average African-American genome, for example, is nearly a quarter European, and almost 4 percent of European Americans carry African ancestry.

Until recently, “human population geneticists have tended to ignore the U.S.,” says Joanna Mountain, a geneticist and senior director of research at 23andMe, a company in Mountain View, California, that offers genetic testing. With its long history of migrations from around the world, she says, the country was “considered to be kind of messy in terms of genetics.” But Mountain and her colleagues thought they might have a fighting chance of deciphering Americans’ complex genetic ancestry. Their secret weapon? 23andMe’s huge database of genetic information.

The team started by looking at the average genetic ancestry of the three largest groups in the United States: European Americans, African-Americans, and Latinos. Those categories are based on how 23andMe customers defined themselves. But as you might expect in a country where different groups of people have been meeting and mixing for hundreds of years, the genetic lines between the groups are quite blurred.

Read full, original article: Genetic study reveals surprising ancestry of many Americans