A Segment-ology TIDBIT

Bottom Line Up Front (BLUF):

1. Email GEDmatch Matches with Ancestry kits to identify their AncestryDNA Profile.

2. Use Ancestry tools to extend the Ancestry of DNA Matches at other companies.

As mentioned before, genetic genealogy is a combination of genealogy and DNA. Another way to look at it is: genealogy with a DNA tool. The foundation is our genealogy – we want to build it out and we want to get it right. That’s were the DNA comes in. Each segment of our DNA comes down to us from a specific line of our Ancestors to our mother or our father, and then to us. People who share the same DNA segment (called segment Triangulation), are related to us somewhere on the Ancestral line we got it from.

In the practice of genetic genealogy, we look for Common Ancestors (CAs) with our DNA Matches; and we look for DNA Matches who share the same DNA segment. Finding the same DNA segment can be done through DNA Painting, and/or by segment Triangulation (forming Triangulated Groups (TGs)), and/or, roughly, by Clustering. Because it is a precise process, segment Triangulation is generally considered to be the gold standard. 

Our search is for DNA Matches with Common Ancestors AND specific segments.

The problem is that AncestryDNA does not reveal the needed DNA segment information. They have the largest database of DNA Matches, and, by far, the best Trees. Yes, many Matches have Private, or no, or skimpy Trees, but still: AncestryDNA has a much higher percentage of Matches with decent Trees than any other company. On the other hand, the other companies (23andMe, FamilyTreeDNA, MyHeritage and GEDmatch all provide the detailed shared DNA segment information, and tools to determine if these shared segments Triangulate. But the genealogy side of these companies pales in comparison to AncestryDNA – in numbers, quality and useful tools. For example I have identified over 4,400 CA-Matches at Ancestry, and only 575 CA-Matches at the other 3 companies (a few are Matches with multiple CAs). However, at each of the other 3 companies, I’ve grouped all my DNA Matches (with IBD (true) DNA segments) into my 372 Triangulated Groups. In other words, I have Common Ancestors for all 84 of my known 128 5xG grandparents (roughly 3/4 of my Tree at that generation); and 372 TGs that cover all of my DNA – if I could only link them together…

The effort now is to: 1) find segment data for Matches at AncestryDNA; and 2) find CAs for Matches in TGs at the other companies.  The following two “tricks” have helped me a lot.

Trick 1. Email Matches at GEDmatch who have a DNA test from Ancestry. My standard email:

Hello – we share a DNA segment at GEDmatch (I am kit M200…), and I’d like to determine our Common Ancestor. I will do the research and report back to you on what I find. All I need from you is a link to your Profile at AncestryDNA – this could be your AncestryDNA user name and/or the URL of your Tree. My Ancestry user name is jimbartlett1; and my Tree URL is https://www.ancestry.com/family-tree/tree/20620230/

Hope to hear from you… Jim Bartlett email: jim4bartletts…

Please be sure to follow up and report back to each Match who cooperates.

Trick 2. Use Ancestry tools to extend the Ancestry of DNA Matches at other companies (where we already have segment data). Some of our Matches at these companies provide some information about their Ancestry – even a little bit may be enough. However, I cannot sugar coat this – it’s work! But Matches who share larger segments should be closer cousins – the Common Ancestors should not be very far back. For Matches in key TGs, I actually work on a quick and dirty list of their Ancestry – an Ahnentafel list – 2 parents, 4 grandparents, 8, 16… usually by this time I’ve picked up a probable thread, if not the actual CA. Sometimes the Match has true dead-ends and a CA cannot be found – but often a CA can be determined. More on this process in a recent blogpost here.

Neither of these two Tricks will guarantee success, but they may be helpful if you are Painting or Clustering or Triangulating or just researching your genealogy. I use them regularly. NB: To link a CA to a TG segment (mapping), we need corroborating evidence – certainly genealogy Triangulation with close cousins, and Walking the Ancestor Back for more distant ones.

[22BA] Two Tricks TIDBIT by Jim Bartlett 20210709