Wednesday, February 16, 2022

D N A : Many Matches, Many Approaches


Some people treat DNA testing as a sure thing, the answer to all our genealogical research problems—and in many ways, that can be true. But when we're approaching a messy stack of DNA matches with a presumption—at least at AncestryDNA—that the subscriber's accompanying documentation is pristine, well, we're bound to be disappointed. Even DNA requires our due diligence to untangle some messy knots.

In the case of my second great-grandmother—so close, and yet so far away—Catherine Laws Davis has presented a research problem in that I can't determine who her parents were, even with the help of DNA testing.

That's not to say I don't have options. I can, of course, look at her suggested matches at Ancestry's Thru-Lines tool. But when I look at her own tile on the lineup of direct ancestors at the Thru-Lines listing, all that is presented to me are two matches, both of whom descend from her other children, collateral lines to my great-grandfather, William Davis. Each of those matches represents tiny genetic connections to me, one at twelve centiMorgans, the other at sixteen. Still, I already have them accounted for in my tree. Connecting DNA matches from collateral lines to my first great-grandfather is a piece of cake, in my opinion.

The trouble is, in order to find any specific Laws matches, I need to step back one more generation, to Catherine Laws' parents. But wait! Those are the exact people I don't yet know the identity of, so how can I take a step like that?

Easy enough, according to Ancestry. They have a handy-dandy way to estimate who those ancestors might be: through the multiple trees posted by Ancestry subscribers onto their website.

And we all know how well-researched each and every one of those trees is.

If we go by Ancestry's guess and look at my DNA matches who descend from my supposed third great-grandparents, my Catherine's own parents, my DNA match count magically doubles from two to four people. Still, of those four matches, the centiMorgan count is so low, it borders on the chance of being Identical by State rather than Identical by Descent. In my case, these four DNA matches share 8, 9, 11, or 12 centiMorgans with me.

If I follow the Thru-Lines suggestion for the next generation removed—in other words, Catherine Laws' suggested paternal grandparents—the count of DNA matches skyrockets to twenty one. And yet, how can I be sure that the Thru-Lines suggested ancestors are correct—especially if they are merely drawn from subscribers' trees? Could these matches be related to me via other familial connections?

There may be a few complicating factors in researching my second great-grandmother, Catherine Laws. Before we begin talking science and genetics, and even before we delve further into the paper trail of her genealogy, let's take a look, tomorrow, at some facts about the setting in which she was born, and in which she got married, raised a family, and spent her later years. Some details about the communities in which she spent those stages of her life may reveal some clues to help us understand some pitfalls inherent in this search. After that, we can examine an alternate approach to depending on the Thru-Lines readout.


  1. Thank you. I hate to confess how many years in I am with my DNA testing, but I still feel like a newbie. First, I can appreciate I have too easy of a time since I am the 7th generation of my mother's family to live in the same county, a county with good record retention and a county recently visited by members of Family Search who were busy scanning and posting records. But, I have a 3rd great grandmother (and I am a little fuzzy on her daughter/gggrandmoter) who is a mystery. Every one of her children gave her a different first and maiden name; the only thing I know for sure is she died as Mrs. Grandfather's name. According to True-Lines I have a name and 23 DNA matches to her, ranging from 9-1419. But the person on all those trees has documents and records to show she was never married to anyone in my tree, was states away from any descendants, the location she lived her whole life is no where near the prior locations of any descendants. It is intimidating to me that everyone else thinks that this is the right person, but I just can't seem to match her to anything. I do have to remember - don't believe anything until you prove it to yourself. I think I am part of a family that seems to love to cut and paste from others.

    1. Don't let yourself feel intimidated, Miss Merry! You have got it right: "don't believe anything until you prove it" for yourself. Develop a solid proof argument from the documentation you find and forget all those copied trees. Let the paper trail reveal the real story...but remember, not everything can be found online. This may take rooting through some records locally in person.


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