Using historical records has been the most traditional way to shed light on the dark stain of slavery in the United States. Now, per new research that the Scientist calls "the largest DNA study to examine African ancestry in the Americas," gene analysis is helping put more pieces of the puzzle together. In the study in the American Journal of Human Genetics, scientists from 23andMe examined DNA from 50,000-plus participants from coastal West Africa, as well as from the eastern shores of North, South, and Central America where enslaved Africans would have disembarked. The study's subjects all gave the OK for their DNA from this "extraordinary" dataset, compiled over a 10-year period, to be analyzed, then compared with a historical database on slavery and info from historians. Much of the researchers' findings confirmed already established information.
But there were surprises, including "the amount of Nigerian ancestry in the US," study co-author Steven Micheletti tells the New York Times—a find researchers at first thought was an error. That's because that discovery didn't sync up with records tracking how many captive Nigerians had been brought to the US on ships from Africa. But researchers now have some theories on that discrepancy, per NBC News: After digging around, they discovered enslaved Nigerians were often brought to the British Caribbean first, entering the US from there later. Natives from Nigeria may also have migrated to places like Angola and the Congo before being enslaved and brought to the Americas. Scientists also found an "ancestral sex bias," meaning enslaved women contributed more to the gene pool of today's African Americans than enslaved men did, per the Scientist. Why that may be: Enslaved men often died young, while enslaved women were raped and made to bear children. (Read more slavery stories.)