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Melting pot? Not in the USA. Yet. But coming soon?

The U.S. as a melting pot, a harmonious and delicious blend of ethnicities from the world over, is a sturdy myth about this country that dates from its founding. The melting pot concept originated, Wikipedia says, in the 1780s, soon after the nation became one. That idea was solidified in a 1908 play of the same name.

“America is God’s Crucible, the great Melting-Pot where all the races of Europe are melting and re-forming!” wrote the play’s author, Israel Zangwill. Only people of European ancestry were stirred into Zangwill’s melting pot. He seems to have been completely ignorant of the First Americans, the slaves dragged in chains from Africa, and the Chinese conscripts who built the railroads in the 19th century. And of course in 1908 the Latino influx, and the immigration of many more Asians and genuine Indians, was several decades away.

The melting pot was fed to me in elementary school, and perhaps to you too. A soothing ideal, but one that has been debunked repeatedly. The most recent debunking, published in December in the American Journal of Human Genetics and free to read, is perhaps the first one based on genetic science—although I’m not sure the researchers would welcome the interpretation that their study showed the melting pot to be largely still a myth, particularly for European Americans.

Genetic Debunkery

The research is noteworthy in particular because it is by far the largest U.S. population genetic study ever. Information about more than 150,000 study subjects who had consented to have their (anonymous) data used in research was drawn from the massive databases of the direct-to-consumer genetic testing company 23andMe. Previously, the country has been considered so messy, genetically speaking, that geneticists have avoided studying it, according to Joanna Mountain, senior director of research at 23andMe.

The study focused on self-identified African Americans, European Americans, and Latinos across the United States. But note that, huge as it was, the sample was also anything but random: It was heavily skewed, consisting as it did entirely of people who had the means to pay, often hundreds of dollars, to indulge their genealogical curiosity.

And the study subjects were overwhelmingly of self-identified European ancestry—148,789 of them. There were only 5,269 self-described African Americans and 8,663 Latinos. One of the authors, Harvard geneticist David Reich, acknowledged that the the work suffered from survey bias—although he also pointed out that the data were consistent with much smaller previous studies.

DNA originating in Europe, Africa, and the Americas was found in all three groups, but the proportions varied substantially. Comparatively few Americans of European descent—only 3.5 percent—possessed 1 percent or more African genes. (Even 3.5 percent is still a lot of people, of course, estimated at more than 6 million.) European Americans with African ancestry are found at the highest frequencies—about 12 percent—in southern states, the genetic legacy of slavery. So too the highest levels of African ancestry among self-reported African Americans, although that was on average less than 75 percent, especially among those in South Carolina and Georgia. (And less than 1 percent Native American.)

It is no secret that African Americans possess a lot of European DNA. In a way the study simply quantifies old news about American admixture. It’s long been known also that nearly all non-Hispanic whites have only European ancestry, but that many blacks have “white” genes because female slaves were simply chattel to their masters. It’s not really news either that these European genes among blacks vary with geography, being most dense, not surprisingly, in the former slaveholding states.

Latinos in the study, on average, possess 18 percent Native American ancestry, with about 65 percent European DNA and a little over 6 percent of DNA originating in Africa. That’s entirely in line with the population history of Latin America.

Beyond the melting pot

Although some reports have have treated the 23andMe data as confirming the idea of the U.S. as a melting pot, the geneticist-blogger Razib Khan argues straightforwardly that the study demonstrates that we’re not much mixed at all, especially European Americans.

“What genetics is showing is that in fact white Americans are shockingly European to an incredibly high degree for a population with roots on this continent for 400 years.” (Emphasis Khan’s.) It’s amazing, he says, that in the U.S. indigenous people had so little demographic impact and that more people with only some black ancestry still don’t self-identify as white. The reverse trends are common in South America.

History, he says, offers some explanation for North-South genetic differences. In the U.S., Native American populations were smaller and often killed off by wars and imported disease, which was less often true in South America. Also, the original European immigrants to New England had some of the highest birthrates ever recorded. In other parts of the country the new settlers sometimes consisted of entire European villages.

Khan’s theory about the explanation for admixture differences between North and South America is that lots of women were among European immigrants to North America, which reduced the amount of intermarriage and made it difficult for children of mixed ancestry to rise in society. But the mostly Spanish original invader/immigrants to South America were nearly all male and often polygynous. This explains why mixed-blood South Americans could become prominent and part of the elite. South American mtDNA lineages are mostly Native American because mothers were mostly Native American.

So the U.S. is still not really a melting pot today. But Khan forecasts that the reality soon will be much closer to that myth.

“If 23andMe did a survey of American genetics 25 years from now I’d be much more amenable to the interpretation that the media is putting on this survey.  In one generation the world of the Baby Boomers, American, black and white, will be gone,” he said.

Even many people who know that their ancestry is not entirely European will self-identify as white, he says. That will bring the situation in the U.S. much closer to the one in South America, where you’re white if you look mostly white and your ancestry is mostly European.

Tabitha M. Powledge is a long-time science journalist and a contributing columnist for the Genetic Literacy Project. She also writes On Science Blogs for the PLOS Blogs Network. Follow her @tamfecit.

Additional reading:

Claims that US is a genetic melting pot appear overblown–if you’re white. Genetic Literacy Project

Genetic Atlas: Human history of moving around and fooling around. New York Times

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