Small Segments At Work
I have Match A at 25cM with no Tree; but a nephew at 1773cM, Match B who has a Tree. Match B is a 3C3R on my Ancestor 16P. Analysis of the 1950 census and his grandmother’s obit, gave me the same name as Match A and a place in my Tree. Match B is 9cM to me. Match B has another uncle at 1771cM, Match C. Match C is also listed by name in the grandmother’s obit. Match C is 8cM with me. And, sure enough Match A and Match C share 2315cM [siblings] with each other [corrected 7/9/2024].
This is about as solid as it gets. Clearly the 9cM Match B and the 8cM Match C are true cousins to me, per genealogy. Each of these Matches share one DNA segment with me. Although this data doesn’t “prove” these 3 segments are the same and linked back to our MRCA 16P, I’d be willing to wager that an upload to GEDmatch would show these segments would Triangulate; and match many other segments from MRCA 16P. In a genealogy sense it doesn’t matter: these Matches belong in my Tree – with or without a DNA link.
I find this example compelling. The old saw: when you hear hoofbeats, think horses. Yes, zebras are a possibility, but the odds in the USA are way in favor of horses. These individuals show up as DNA Matches to me – they share a segment of DNA with me. Some segments are small, some are large. When they come from such a tight fit in one part of my Tree, I’m inclined to believe that they are the same segment. It is “possible” that they each got a randomly different segment, or even false segments, but the logical reasoning is that they share part of the same segment from an MRCA. Why not just accept that for now? Perhaps, someday, some alternative will come up – even so, it would not change the genealogy backed up by records.
Icing on the cake – in reviewing Match C’s shared Matches, Match D (8cM to me) is 3476cM (a daughter) of Match C – another add to my Common Ancestor spreadsheet and to my Tree.
Bottom Line: ProTools is providing a lot of great bread crumbs to follow; and linking a lot of small cM Matches to my Tree. Be sure to scroll to the bottom of a ProTools Shared Match list, looking for high cM interrelationships! Don’t discard genealogy “finds”, just because they share small cMs.
[22CM] Segment-ology: ProTools Part 5 Small Segments At Work; by Jim Bartlett 20240707
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Maybe I’m at a different stage of the game, but I already have a few clusters of matches I’ve been able to link to ancestral couples in the 1700s or early 1800s, sometimes with triangulated segments for those on MH or GEDMatch, but still no idea how that ancestral couple connects to me (I’m pretty sure which of my grandparents and have theories about GGP, but that’s it). Or in one case, three ancestral couples born in the early 1800s (in different states) who have matches who triangulate between me and more than one of the three couples, but again no idea how those three couples relate to each other or to my ancestors.
I’ve done the genealogy, built trees for these couples, sometimes found their parents and grandparents (and sometimes not — 17th/18th century paper trails being what they are), still no luck.
Have you seen anything in Ancestry Pro Tools that will help here? Finding new 2nd or 3rd great-grandchildren for those couples doesn’t seem like it’ll be illuminating.
I already have my matches in spreadsheets, though with a different layout than yours :-).
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LJ, Many of us tout the ProTools ability to take a large segment Match with no tree, and show us a small segment Match with a large Tree (including our MRCA) who is a child of the large segment Match – BINGO, we now know both are related to us. But in addition to these are 20 to 200 Matches who run the range from 20cM to over 100cM for any Match we have (I’ve saved some down to 6cM). I think it would be well worth it to subscribe for one month and test it for yourself. Read over my ProTools posts (more coming) to get the feel for how it works. It’ll probably be a while before I get to my 8C MRCAs, but I’ll probably post on each generation on how it’s helped me. Good luck. Jim
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Jim, I think you have a typo in Pro Tools 5, but I’m not sure where. Two sentences (“And, sure enough Match A and Match C share 3476cM [siblings] with each other.” and “Icing on the cake – in reviewing Match C’s shared Matches, Match D (8cM to me) is 3476cM (a daughter) of Match C – another add to my Common Ancestor spreadsheet and to my Tree.”
I’m guessing the first one since you say Matches A and C are siblings. But if this one has the correct cM, were looking at a parent-child relationship, aren’t we?
Regards,
Doug
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Doug, It is convoluted – I should have drawn the picture. A and C are siblings, and D is a daughter of C. The typo is that A and C share 2315cM (siblings). Thanks – I’ll correct it. Jim
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Jim, are you using DNAgedcom.com for your Ancestry kits? The CLMs that they provide would get you there a lot quicker. I’m following your blog, but I still don’t see that Ancestry is providing anything worth the first $10. And I don’t intend to just be negative (and it is certainly not directed at you). DNAgedcom has a better payment method as well. It’s $5 a month and very easy to turn on and off. But it also augments FTDNA, My Heritage and GEDmatch on a chromosome matching level with CMA (Chromosome Matrix App) so you are getting SO much more for $5.
my 2 cents
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Ray. Good advice. I’ve been a DGC subscriber since the beginning. I used a full download to develop my Walk The Clusters Back process. As a result of WTCB, I was able to impute Ancestors and TGs to virtually all of my Matches down to 20cM and many more below that. They are sure a help with ProTools now, and almost all of the imputations are coming true, or very close. DGC has been on-and-off for a while – Rob is getting close again (follow DGC Users on fb) – but I don’t think the ProTools shared cMs will be included for a while. And that bit of info is extremely helpful at Ancestry – where most of my Matches are. Jim
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I’ve been finding many examples like that as well, though usually higher than 8 cM, but seems like I’ve found one or two that low as well. This is a fine example of how small segments matter IF they cluster.
I’m now going through the top 600 matches (the cutoff for that is 43 cM on the kit in question). I’ve now placed exactly around 520 of the 600 – with an occasional “Private” for a living person that I couldn’t figure out. On the remaining 80, the vast majority I have determined who their great grandparent is, just not how they exactly connect. That number was closer to 400 two weeks ago. I believe I’ll work on these much easier strong matches before diving into some clusters with a bunch or 20-30 cM matches just to get a feel for how to best use this tool.
It’s most assuredly a game changer. Cheers.
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Brian – Thank you – it’s reassuring when our experiences mirror each other. I don’t start with the small cM Matches, I find them as very close Matches/relatives to Matches who are in a group I’m working on (right now that’s my 16P Ancestor, with the other 2xG couples in the on-deck circle). As you point out, when they Cluster, they are solid. In that vein, I’m going through all Matches (about 80) who descend from 16P, and making sure they match several of the others. So far there is only one standout – a proposed Civil War soldier who fathered a child. There are NO Shared Match Matches above the noise level. I’ve got about a dozen left to check – then on to Ancestor 18P…
Like you, still working on the “best” way to squeeze the most from this tool. Jim
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