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Don’t take ThruLines as gospel either

So a couple of weeks ago The Legal Genealogist focused on the dangers of uncritical acceptance of the automated systems at the DNA testing companies that link us to possible/proposed ancestors by showing how one suggested Theory of Family Relativity at MyHeritage couldn’t be correct.

Based on nothing more than trees that shared a same-name person — Matthew Johnson — MyHeritage had me linked to a family I can’t be linked to, at least not in that way.1

Today let’s share the love.

Here’s one from Ancestry’s ThruLines that’s just as bad.


One of my nemesis ancestors is George Washington Cottrell (b. c1821, probably in Kentucky; d. 1891 in Texas). He was a thorough-going scoundrel whose early appearances in Texas records generally have him running one step ahead of the law.2 Finding even a clue to George’s parents would be terrific.

But the most recent iteration of Ancestry’s ThruLines for George isn’t going to help one bit.

Because, it suggests, his mother was Mary Parsons of West Virginia, who married Thomas H. Cottrell, and had a son George Washington Cottrell, born in 1820-1824.

Opening up the Evaluate button to examine this theory, ThruLines tells me that “None of the trees linked to your DNA matches identify Mary Ann Parsons as the mother of George Washington Cottrell.” So, to begin with, nobody who has tested and who matches my DNA descends from the Cottrell-Parsons family of West Virginia.

ThruLines then tells me that “8 other member trees identify Mary Ann Parsons as the mother of George Washington Cottrell.”

Okay. But there are a few problems with those identifications:

1. Not one of the trees cited as support for George-as-son-of-Mary has so much as a single documentary source for linking any George as a son to Mary, much less my George. The sole citations are to other family trees.

2. All of the trees that do list this George have him well-documented via census records as living in Ohio without a shred linking him to Texas, at a time when my George is equally well-documented in Texas.

3. All of the trees that do list this George have him marrying a different wife than my George, and having different kids from my George, all at the same time as my George.

4. If the trees are right, this George died 16 years before my George.

In other words, this is another same-name-therefore-same-person suggestion.

And if that’s not enough, this particular Cottrell line in West Virginia? Their YDNA says it’s not the same Cottrell family at all. At the basic 12 marker level, we only match at eight of 12 markers. At 25 markers, it’s 15 of 25 markers. The genetic distances only increase as the number of markers tested increase: this isn’t the same family line.3

This isn’t something I’m guessing at. I know this family really well. You see, I happened to research this West Virginia family pretty thoroughly some years ago as part of my kinship determination project for certification by the Board for Certification of Genealogists; my brother-in-law is collateral kin to this family. And no, we’re not the same Cottrell line at all.

Again, I want to stress that these tools are wonderful sources of hints and clues.

But they’re not more than that.

They’re not proof.

And we shouldn’t accept them without critical analysis.

The best tool we have is the grey matter between our ears.

Cite/link to this post: Judy G. Russell, “Equal opportunity DNA criticism,” The Legal Genealogist ( : posted 11 Aug 2019).


  1. Judy G. Russell, “Just a theory,” The Legal Genealogist, posted 21 July 2019 ( : accessed 11 Aug 2019).
  2. See Judy G. Russell, “George Washington Cottrell of Texas: One Man or Two?,” National Genealogical Society Quarterly 105 (September 2017): 165-179; pdf online at the Board for Certification of Genealogists Genealogical Work Samples page ( : accessed 11 Aug 2019).
  3. Cottrell FamilyTreeDNA Project – Y-DNA Classic Chart,” ( : accessed 11 Aug 2019), comparing the West Virginia Cottrells (Group 2) with the Virginia Cottrells (Group 3) to which my George belongs.
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