Lead author Katarzyna Bryc from Harvard Medical School and 23andMe and colleagues analyzed the genomes of over 160,000 European Americans, Latinos and African Americans to take an in-depth look at how different genetic ancestries are from each other in the U.S.
Bryc explained that the study not only sheds light on the historical underpinnings that genetic ancestry's regional differences have but also uncovers the complex relationship of self-identified ethnicity and race and genetic ancestry.
Over the last 500 years, Africans, European settlers and Native Americans have been mixing together in North America. While most of the world is characterized genetically, the same cannot be said about the U.S., what with less attention trained on the country's complex patterns of ancestry. There's also the fact that the relationship between self-described ethnic and racial identities has not been reconciled with genetic ancestry.
To paint a clearer picture of ancestry in the U.S., the researchers analyzed variations in DNA sequences known as single-nucleotide polymorphisms in 148,789 self-described European Americans, 8,663 Latinos and 5,269 African Americans. These subjects already participate in research done by 23andMe, allowing their data to be used and completing surveys.
According to the results of the study, regional differences in ancestry are reflected in historic events, tied to major occurrences like waves of immigration. For instance, 10 percent of European Americans in Dakota and Minnesota are of Scandinavian ancestry whereas it is only present in trace amounts in most other states.
Additionally, most subjects identify with majority of what runs in their DNA as opposed to expectations that they conform under a "one-drop rule." Over six million Americans self-identified as European might actually be African in ancestry and up to five million self-described European Americans will have at least a percent of Native American blood.
Bryc said that their study suggests that numerous individuals that are part Native American and African in ancestry have been welcomed into the white community without trouble, undermining cultural labels used to segregate individuals into subtle but non-overlapping groups.
She added that when taken together, the results of the study hint that genetic ancestry may be used as leverage to change historical records and affect cultural processes responsible for molding the modern population.