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Just where did that Sub Saharan African ancestry come from?
October 18, 2013 - Andrea Johnson
My decision to have my DNA tested by the company 23andme has led to more questions than answers about my family tree in the last few weeks.
For instance, there are four people who match me and each other on a particular chromosome and I have no idea how we might all be related. They live all over the country: one a black man from somewhere in New York City who had family roots in North Carolina; another a white woman who had some ties to Indiana; another a white woman who had ties to Missouri. Based on locations alone, I have my suspicions that the connection might be through my one branch of the family. Among my many times great-grandparents were people who lived in North Carolina and Kentucky and Tennessee before they made their way to Indiana and then on to North Dakota.
A small percentage of whites who are tested through 23andme have some Sub Saharan African admixture, according to the site, which claims that there are about 3 to 4 percent of their white customers who have "hidden African ancestry." It turns out that I am among them. In my case, the Sub Saharan African ancestry is about 0.4 percent of my genome. Most whites with some hidden African ancestry have between 0.5 to 0.75 percent African ancestry. That percentage is so vanishingly small that I don't know quite what to make of it. There were no indications of such ancestry in family stories or in the family tree, which shows overwhelmingly Scandinavian, French, German and British and Irish ancestry.
This could be a testing glitch. It could also be the remnant of some ancestry from thousands of years ago, when all of our ancestors lived in Africa. Perhaps it came in from some ancestor who lived in Europe. At least according to Wikipedia, almost all Southern Europeans have inherited some small percentage of Sub Saharan African ancestry, ranging from 1 to 3 percent. It is supposed to go back as far as 55 generations, maybe to Roman times. Since 23andme also claims that I have a small slice of Southern European DNA – where it comes from, I'm not sure, though I seem to have a bit of Swiss ancestry several generations back and there are Italian-speaking Swiss – it's possible that this is where that 0.4 percent of Sub-Saharan DNA comes from.
And, of course, it could also be an indication that some 200 or 250 years ago, I had one great-grandparent who was black or mixed race, who probably lived somewhere in the South. This was probably fairly common back in the Colonial era, based on what I know of history. There were interracial marriages between black slaves or free black servants and white indentured servants, as well as between other people of different races. According to 23andme, it is also possible that I have 0.1 percent American Indian ancestry.
I know the names of many of my ancestors who lived back then and, in many cases, where they were born or where their parents were from. I know whom they married and who their children were. But the names alone don't give anything away about what they looked like or whom they loved. In some cases, there are written wills and historical anecdotes that have been passed down from generation to generation, but they can't answer all the questions I have. This particular mystery is likely to go unsolved. As I told my cousins, there is no real way to know, but it is certainly an intriguing discovery.
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