A Few ThruLines Are False, and Some are Misleading

A Segment-ology TIDBIT

I made a spreadsheet of my 1,820 ThruLine Matches – to track and analyze them all. I found 86 were questionable (some of those 86 were clearly wrong, and others were iffy – I just didn’t have the information (or time) to sort it out. 86 is roughly 5% of the total, which means I agreed with 95% of my ThruLine Matches. Note a few of my Matches are double counted because they shared more than one Common Ancestor with me.

A high percentage of ThruLine Matches were good, giving me confidence in this tool.

Of my ThruLine Matches, 145 of them had uploaded to GEDmatch (or tested at other companies). I found one of the 145 (1.5%) had a false Shared Segment with me – it didn’t match a Triangulated Group on either side. I also found that 15 of these Matches (10%) with segment info had TG segments with me which were on a different one of my grandparents than the ThruLine Common Ancestor. This is not necessarily an error by ThruLines (the Match is very likely still a genealogy cousin on the ThruLines Common Ancestor), but in each case the DNA Shared Segment indicated we should have another Common Ancestor on a line from one of my other grandparents. Most of the 15 Matches were on the wrong side – the ThruLines Common Ancestor was on one side, and the Shared DNA Segment was on the other side.

So, from this small sample, about 10% of the ThruLines Common Ancestors may be misleading from a genetic (or chromosome mapping) point of view.


[22AK] Segment-ology: A Few ThruLines Are False, and Some are Misleading TIDBIT by Jim Bartlett 20190729e

10 thoughts on “A Few ThruLines Are False, and Some are Misleading

  1. As we are months since TL started I have found a number that are correct. The real problem for me is that my 2nd GGF in the McClure line was a NPE as shown by my FTDNA Y-DNA. I still get TL’s using various McClures almost all of which are in the McClure surname project list, non of which I share enough DNA with to even consider them as ancestors. Since my 2nd GGF was the oldest child my 3rd GGM may have been his mother. Other than her given name Mary nothing else is known about her. I have notified Ancestry of the DNA disconnect and even removed my 3rd GGF from my tree I still get TL’s for the known non matches. They have never given me a TL for my 3rd GGM though. I believe that if Ancestry would try in some fashion to use some of other DNA sources or even use the information they are given by folks such as myself TL could be improved. Years ago when they had their earlier test they took uploads of FTDNA both Y and mt and gave us matching to the testers in their DNA kits.


    • James, Please read my latest two posts on Walking The Clusters Back – if you can identify Clusters at the GGF level, then gradually lower the Matches in those Cluster go – on to other more distant Clusters, which might give you some clues. Jim


  2. Pingback: AncestryDNA and Other Goodies (a test covering this will be given at the DNA Sig) | Monterey County Genealogy Society

  3. Pingback: How Does ThruLines Work? | segment-ology

  4. How did you determine that so many of your matches had uploaded to GEDmatch? Assuming there hasn’t been any contact, my experience has been a bit of a crapshoot in determining if a match is also at GEDmatch. If they haven’t uploaded a GEDcom or their name and/or email doesn’t match up with their ancestry Member ID or who I know them to be, then it usually seems very difficult if not impossible.


    • Brian,
      Bad assumption – I message almost every Circle and Shared Ancestry Hint – and I’m working my way through all of my ThruLine Matches.
      1. I ask them all to upload to GEDmatch.
      2. Like you, I try to determine the AncestryDNA name for each Ancestry Match at GEDmatch – some make it easy, some don’t.
      3. Failing that, I send an email to Ancestry Matches at GEDmatch and ask for their AncestryDNA name.
      This pretty much keeps me busy, so I haven’t tried finding them on facebook…

      I cannot stress enough, the value of contacting Matches. Jim


    • I didn’t download my ThruLines Matches, I type them into a new spreadsheet – with cM, cousinship, Common Ancestor and at two generations down toward the Match. It took about 3 weeks with some very late nights. And then I entered key data into the Notes boxes for each one. I’m now cycling through the whole list again, sending messages to each Match – expressing the hope they’ll upload to GEDmatch. It’s not easy, but it is finite. Jim


  5. Vanessa,
    I think ThruLInes starts with whatever they can find in my Tree and my Matches Tree – and they use our respective lines in the comparison. When my Match only goes back to her grandfather – TL uses that, and then picks up with what I have in my Tree. If neither of us has the actual link, they look at other Trees that overlap mine and/or my Match’s. That’s a lot of computer work for 15-20 million customers. And I’m sure there are glitches – I’ve found several Matches who are in fact genealogy cousins, but not the way TL figured it out. However, all things considered, I think they are doing a great job – much better than anyone else (except you and me, of course;>). AND on the right hand side, they offer a lot of Trees and records to back up their version – again, not always right, but often including new records and other tidbits. Jim


  6. Thank you for sharing your work with Thru Lines. I like the new feature that lets me review the descent to a DNA match and then add the missing “link” to my tree. However it is frustrating to note that in many cases the “link” is already in my tree but Ancestry can’t recognize it, and I often can’t discern a cause. Sometimes Thru Lines even offers my own record of that person as a match, not recognizing it is my own tree, linked to my DNA they are creating a match with. Totally baffling!

    Liked by 1 person

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