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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.

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“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 23andme.com 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.

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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.

Taking a closer look at the results you sent us, we see that your father has the highest amount of sub-Saharan ancestry, at 1.4 percent, all identified as originating in West Africa. Your mother has a smaller percentage of sub-Saharan African DNA, with 0.5 percent identified as West African and 0.1 percent as unassigned sub-Saharan. You also provided us with 23andMe’s chromosome view, which shows the breakdown of ethnicity by each pair of chromosomes.

Interestingly, the chromosome view of your fathers’ results shows larger bands of West African ancestry on two different chromosomes. The bands on your mother’s DNA are much smaller. This suggests that the African ancestry on your father’s side may be more recent than your mother’s.

How DNA Testing Can Help Trace Your African-American Ancestors

So, you see, it is indeed possible that you have recent African-American ancestors. Perhaps by finding out exactly how your African-American ancestor fits into your family tree, you will have a better understanding of what this means for your own identity. You can approach this research in several ways.

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Because your father has more African ancestry in his DNA results, you may want to research his line first. You can do this by reaching out to relatives on his side of the family to see if they know anything about their own heritage.

In addition to this, as you may already know, 23andMe offers DNA Relatives, which helps put you in touch with those who may be genetically related to you based on your tests results. FamilyTreeDNA offers a similar service called Family Finder, which complements its y-DNA and mtDNA tests. Ancestry.com is also a treasure trove of connections to recent genetic cousins.

Using such a service, you may be able to find others related to you who also have African ancestry in their DNA. You can look for distant relatives who may have done additional research on this line, or maybe they have their own family stories that may shed some light on common ancestors you might have. This may also be helpful in researching your great-great-grandmother who was adopted in Indiana in the 1800s, since it may be difficult to trace her ancestry using traditional methods.

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With that said, you may also want to revisit the paper trail of your ancestors. By connecting with close genetic matches on 23andMe, you may find that there are certain U.S. geographic regions where you found other relatives who also have a percentage of African-American ancestors; this can give you some key regions in which to focus your search.

Since your father’s side of the family was primarily from Texas, you can begin researching his family there using census and vital records to see if you can find any indication of your ancestors’ race. Hopefully, by using your DNA results, reaching out to other relatives and finding your ancestors in paper documents, you can begin to find clues to your African-American ancestry.

Henry Louis Gates Jr. is the Alphonse Fletcher University Professor and founding director of the Hutchins Center for African and African American Research at Harvard University. He is also editor-in-chief of The Root. Follow him on Twitter and Facebook.

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Send your questions about tracing your own roots to TracingYourRoots@theroot.com.

This answer was provided in consultation with Kristin Britanik, a researcher from the New England Historic Genealogical Society. Founded in 1845, NEHGS is the country’s leading nonprofit resource for family history research. Its website, AmericanAncestors.org, contains more than 300 million searchable records for research in New England, New York and beyond. With the leading experts in the field, NEHGS staff can provide assistance and guidance for questions in most research areas. They can also be hired to conduct research on your family. Learn more today.