The United States is often described
as a cultural melting pot. The degree to which that’s true socially can be
debated – and, at least as regards to race, it has been debated lots
lately.
But another way to look at that
question could be to examine the mixing in Americans’ genetic ancestry. And
that’s just what researchers at 23andMe, a genomics and biotech company, have
done. Their analysis of 160,000 Americans revealed subtle differences in
genetic ancestry as it relates to race across the United States.
Americans
Up Close
Anyone interested in tracing his or
her ancestry can purchase a genetic testing kit from 23andMe for $99. The
company will analyze your sample and provide you with a full report detailing
specific information about your DNA. Over time, 23andMe has assembled a massive
database of over 800,000 genotyped customers.
From this broader population
researchers selected 148,700 European Americans, 8,700 Latinos and 5,200
African Americans who had consented to allow their data to be used in research.
Researchers wanted to determine how people’s self-identified races or
ethnicities – in this case, African American, Latino, or European American –
correlated with their genes, depending on which part of the U.S. they were
living in. Specifically they examined traces of Native American, African, and
European genomes by looking for so-called single nucleotide polymorphisms,
one-letter changes in the DNA sequence.
Patterns
of Genetic Ancestry
Not surprisingly, researchers found
that most people have traces of several ethnicities in their DNA, although we
usually only identify as a single one when describing ourselves. What was more
interesting was how this relationship varied by region, often reflecting
historical events from many generations ago.
The slave trade, for example,
brought thousands of Africans to the United States. Most of the major slave
ports in the U.S. were located in the South, which is reflected by a greater
amount of African ancestry in the genomes of both white and African American
people in the South. Researchers estimated that more than 5 million whites in
the U.S. have at least 1 percent African ancestry in their DNA. Louisiana’s high
level of African ancestry in self-identified whites is consistent with
historical accounts of intermarriage in the New Orleans area.
The researchers also found that more
than 5 percent of African Americans carry at least 2 percent Native American
ancestry. The highest proportion of African Americans with Native American
ancestry was in Oklahoma, where black slaves were a significant part of the
population in the 1860s and where the many Native Americans were displaced to
after the Trail of Tears in the 1830s.
Among Latinos, researchers found
that Iberian ancestry (Spain, Portugal) was particularly pronounced in those
from Florida and the Southwest U.S. Researchers believe this ratio probably
reflects early Spanish influence in these regions, as well as recent
immigrations from Latin America.
Here are a few other quick finds
from the analysis, which was published Thursday in the American Journal of Human Genetics:
- Scandinavian ancestry in European Americans is highly localized in Minnesota and the Dakotas.
- Eastern European ancestry was highest in Wisconsin, Illinois and Pennsylvania.
- Native American ancestry in Latinos was highly concentrated in the Southwest with Texas and California leading the way.
A
True Melting Pot
This analysis has its limits.
23andMe isn’t a free service and requires an Internet connection, which are
both factors influencing the data. And 23andMe chose to focus on only a few of
the racial and ethnic groupings in the U.S. due to data limitations.
Researchers believe they’ll learn more about the ancestry of the U.S.
population as they collect more DNA data.
But the results are still revealing.
“Our results reveal the impact of centuries of admixture in the U.S.,” the
researchers write, “thereby undermining the use of cultural labels that group
individuals into discrete nonoverlapping bins in biomedical contexts…”
In other words, we all have a little
bit of each other in our gene pools – a fact that can perhaps help spur
unity in a divided modern world.
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