Genetic genealogy: why more DNA is better

Genetically speaking, my sisters and I are all half Mom and half Dad, right? DNA 101. So, only one of us needs to do a DNA test, and then we’ll all know our ethnic origins, correct? . . . OK, I confess I never took DNA 101. But thanks to AncestryDNA, I have learned the answer is no (at least when it comes to autosomal DNA). The more family members you test, the fuller the picture of your genetic genealogy will become.

Testing the family

I was the first in my family to send my DNA sample to AncestryDNA for analysis. All by itself, it was intriguing! It drew the family around and raised questions. We had become interesting and interested.

Then we added my mother, sisters, and a paternal first cousin — all taking AncestryDNA’s autosomal test. That’s when it got really fascinating.

Perhaps the biggest surprise came from the ethnicity results of a sister who has often been mistaken for my twin.  Look at this breakdown:

Another sister’s results came back showing 97% DNA from Great Britain, while our mother is 52%. This sister must have gathered virtually all the British DNA from both of our parents to have this result.

As I began to look at the results, it finally got through to me that the half-Mom-half-Dad scenario is more like a liquid measure than one of breaking Dad and Mom in half, like a cookie. As we get our half portion of each parent, it could be any mix of DNA segments. And the likelihood of exactly matching a non-twin sibling would be practically zero.

When you look at the results of my sisters and me all together, you get a more complete picture of our heritage. Pooling our results, we find that we have heritage from the Middle East, Caucasus, and North Africa, in addition to what you see above.

Bringing in my mother and my first cousin on my father’s side, we began to be able to sketch out which heritage came from my mother and which from my father. The Caucasus and Middle East appears to be my mother’s heritage, for example.

Do we descend from slaves?

This family group project also helps us with the one genetic genealogy fragment that has us particularly interested — the African ancestry. We know we descend from slaveowners, but do we also have slave ancestors?

Our mother shows African heritage from the south-central part of the continent. Me, all of my sisters, and my paternal cousin, on the other hand, all show ancestry from north and west Africa, centering on Mali, which was a part of the nineteenth-century Atlantic slave trade.

With all of us showing around 2% African heritage, this could place that ancestry around six generations back, which would likely be the early nineteenth century. The presence of the DNA in my paternal cousin means we need to look for this ancestor on my father’s side. And we are looking.

Finding cousins

AncestryDNA also links us to others who have taken the test and show up as cousins, near and distant. It has presented cousin relationships for my sisters that don’t appear connected to me. Had I been the only one in my family to do the DNA tests, we would not have found these connections.

I am not an expert on DNA, and likely never will be. I do know that this science and the methods used by AncestryDNA and other providers are in a process of growth and change. In other words, “doing your DNA” will not be the end of the story for your genetic genealogy.

I encourage those with an interest in DNA to follow another blog: The Genetic Genealogist. It’s host, Blaine Bettinger, knows this subject inside out. He explains two more complex forms of DNA tests that can isolate heritage to mother’s mother’s mother… (mitochondrial DNA) and to father’s father’s father… (yDNA).

I encourage you to test your DNA. And your parents and siblings and cousins. There is no better path to genetic education and genealogical “brick wall” answers.

One day soon, I’ll tell you how we used yDNA to shed light on a long-ago family mystery and discovered that our real family name is probably Winchester, not Cox.

Please tell me your genetic genealogy stories!

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