Do Most Whites Have Traces of African DNA, as I Do?

Tracing Your Roots: Wondering if small amounts of African ancestry come from humanity’s ancient origins or from more recent kin.

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“I have had both of my parents’ ancestry tested by 23andMe, and I have been tested as well. I am ostensibly European, but both parents received West African-ancestry DNA results. I am 1.3 percent West African, which Doug McDonald of the University of Illinois verified as being of Yoruba origins.

“My father has 1.4 percent West African ancestry and my mother around 0.3 to 0.6 percent. Does this mean that one of my great-great-grandparents (I’m not sure how many ‘greats’) was from Africa? Or does this African DNA come from the more distant past, and is it widespread among Europeans? I have no genealogy records to go from, so I am at a loss.

“Both sides of my family have deep roots in the American South: My mother is Cajun, Irish and Canary Islander from southeast Louisiana, and my father’s family is from all over, mainly southeast Texas. His great-grandmother was adopted in Indiana in the late 1800s and moved to Texas with her adopted family. She is listed in the 1910 census as living with them in a mostly black area.

“I notice that there is not a lot of information about European people with sub-Saharan DNA. A lot of my relative connections listed on who are European have maybe 0.1 percent sub-Saharan African ancestry. They also have Iberian results. I have Iberian, as well, but not a lot. I would appreciate your expert thoughts about ‘Caucasian’ Americans, how we should uncover our African roots and what it really means to be ‘white’ or ‘black.’” —Natalie Baker

Determining How Recent Your African Ancestry Is

Perhaps one of the greatest discoveries stemming from recent advancements in genetic genealogy is that previously held assumptions about race and identity are being brought into question. It was always known throughout American history that there was at least some intermixing of races, but only now, through DNA testing, can we see the extent to which this actually occurred.

In the South, the infamous “one-drop rule” was once employed during the Jim Crow era to classify African Americans as anyone who had one drop of African blood. Had there been DNA testing during that time, the segregated South would have looked quite different, since we now know that some people who identify as primarily white actually have some African ancestry as well. New information brought to light by new DNA-testing technologies opens up a new conversation on race and identity.

As you noted, there have been several studies showing that DNA results of many African Americans indicate that they have between 20 and 30 percent European ancestry. These results reflect the fact that many slave owners fathered children by their slaves. DNA tests also show that the opposite of this scenario can be true: Those who identify as primarily white can have African ancestry. 23andMe published a study (pdf) based on its own dataset that concluded that approximately 3 to 4 percent of their customers who identified as being of primarily European descent had at least one ancestor in the last 10 generations who could be traced back to Africa.

Autosomal DNA tests reveal these connections by testing across the entire genome and looking at more recent ancestry. From an autosomal DNA test, you can get an admixture, which shows your ethnicity broken down by percentages. Your test was done by 23andMe and your admixture results were interpreted by its Ancestry Composition system. Other genetic-genealogy testing companies, such as FamilyTreeDNA and AncestryDNA, offer similar tests that also give you admixture results.

Although some DNA tests probe into deeper ancestry, back thousands of years, the autosomal test that you took from 23andMe generally shows more recent ancestry, quite reliably over the last 100 to 200 years—in your case, since the time of slavery, when this “admixing” most likely occurred. Given this information, the African DNA identified in your test is not from ancient ancestors (after all, 50,000 or so years ago, all of our ancestors were Africans, but that ancient DNA has largely disappeared) but, rather, from more recent ancestors, people whose actual identities you could find if you could construct a detailed family tree of ancestors who lived in the last couple of centuries.