Triangulation and Ancestry

+10 votes
405 views

A while back I did a MyHeritage DNA test and was working through matches etc. which worked quite nicely. I could download segment data and put them in DNAPainter which was very helpful. Recently I did an Ancestry test as well which has given me so many more matches, but it appears I can't download the segment match data between matches. This means I can't use them on DNAPainter and more worryingly means I can't use triangulation?

As an example: https://www.wikitree.com/wiki/Treble-45 is my G3Grandfather. I now have 6 DNA matches to relatives that have William Treble + Mary Goss as the MCRA, and they go down 3 different children of theirs (3 different legs). It seems obvious that the matches are correct, but am I right in thinking I shouldn't mark the relationships as "confirmed by DNA"?

I'm hesitant to post data about the matches on here as they are living people

WikiTree profile: William Treble
in Genealogy Help by Matt Steady G2G3 (3.4k points)
retagged by Ellen Smith

If you're new to triangulation, understand that you don't confirm the MRCAs with that, the exception being if you're triangulating with a half-relative in the mix. Unless that's the case, you don't know which ancestor in the pair contributed the segment.

For gt-gt grandparents, it's easiest, usually, to find a suitable 3rd cousin (or a 2C1R in you parents' generation) and confirm them without triangulation. With that kind of confirmation, you get to mark the MRCAs.

So to confirm a gt-gt-gt grandparent, you need to triangulate with people who have your corresponding 4th-gt grandparents as the MRCA.

So it's a mess. The places you can compare chromosomes often don't have the matches, and the place with the most matches doesn't offer chromosome-level comparisons, and it's hard to get people to answer a message, much less upload elsewhere. It seems almost like some kind of conspiracy! wink 

That being said, even when triangulation doesn't help confirm an ancestor, it can still be used to confirm various family lines coming down from those ancestors, and even if you can't do THAT with it, it give you more confidence in knowing where a segment came from, if you're mapping out your chromosomes.

Be aware, also, that if you can find someone in your parent's generation who has a test, who is also descended from you gt-gt grandparents, and then find a 3C of THEIRS, that you can use THAT match (a match that does not include you) to confirm those gt-gt-gt grandparents, without triangulation. I've done a couple of those, myself.

Good luck!

Thank you Frank for your well thought out answer. Yes I think I had roughly pieced that together in my head, but it was very helpful to have it written down like that as it crystallised it somewhat.

And yes - it does feel like a conspiracy!

And the second part about using matches that don't involve me ... sounds obvious in hindsight but I hadn't actually thought of that. I'm not entirely sure where to find the other tests though.

Is there any kind of mentoring program for DNA with WikiTree? I feel like I'm reinventing the wheel when it's all been done before...

It's funny. but this got me reviewing my own situation, and I see I have a 2C1R-3C1R match on MyHeritage that I can use to do another pair of gt-gt-gts! I prefer to use GEDmatch for these things, since any GEDmatch member can verify it, but I'm not sure if I have this kind of match there.

I'm also reminded that I have AncestryDNA matches that would work. The problem there, though, is that on THAT site I'd need one of the two people to tell me the cM of the match, and if it isn't at least  90cM (and about 85% of them AREN'T), AncestryDNA will tell me that the "possible" relation is 4th cousin, or more distant, and that technically disqualifies it from being used through the infamous "#5" in the directions: "If the DNA-predicted relationship does not correspond with your known relationship, more genealogy or DNA testing needs to be done." WikiTree never adjusted for the fact that the AncestryDNA "possible relationships" can be just plain wrong, and 3Cs are where it's the worst! (It's that "conspiracy" thing again!)

If you can get the exact same people, using the exact same test results, on GEDmatch (or probably anywhere else), they can be used just fine, without violating any rules. The above mentioned 2C1R-3C1R combo (3C to each other) only matches a paltry 20.8cM (which doesn't really even seem like it's ENOUGH to confirm both of their gt-gt grandparents!) But My Heritage estimates that it's "3rd cousin - distant cousin" so that's just peachy with WikiTree. On AncestryDNA it has to be 90cM, and that's after they throw away some of the more common DNA segments.

Ahhhhh "they throw away some of the more common DNA segments.".... that explains why the same match as different cMs on Ancestry to MyHeritage. I did wonder...

2 Answers

+18 votes
 
Best answer

Yes, segment data are not available for download for Ancestry.com DNA matches - you cannot do triangulation with them as you can with MyHeritage.com. Unfortunately this means in turn that, for anything beyond 3rd cousins, you cannot use Ancestry.com DNA tests for Wikitree DNA confirmations. A work-around would be to have all the relevant matches upload their DNA to MyHeritage or to GEDmatch. See https://www.wikitree.com/wiki/Help:Triangulation#AncestryDNA_Triangulation

by Anonymous Geschwind G2G6 Mach 8 (82.0k points)
selected by Darlene Athey-Hill
Thank you. Yes that was what I was afraid of. I think it's very unlikely they're going to upload their DNA to another platform if they haven't already.

Is there anything we can put in the bio that shows that they are very likely DNA matches but not actually click the radio button? It would be useful information for other people I'm sure.

You can put a statement in the bio that follows the same basic format as the DNA confirmation statement, but uses the word "supported" instead of "confirmed" - see https://www.wikitree.com/wiki/Help:Confirmed_with_DNA#Genealogy_Supported_by_DNA_but_not_Confirmed_with_DNA

For example, I have put a section on the profile for one of my ancestors (based on a previous version of the guidelines which had minor variations) - see William Wall.

Hey Paul, I just had a look at your ancestor's linked profile.  I just wanted to comment that you've done a very nice job on it with the in-line sources and the images!
Thank you - that's really very helpful
+7 votes
If you haven't already, you might want to reach out to those matches on Ancestry and ask them if they have uploaded their DNA to MyHeritage, FTDNA, or GedMatch. Explain the relationship to you and that you would like to accomplish a triangulation. You might be able to interest a couple of them to do just that or you might find out that they have tested at one of the other companies. It is always worth a try!!
by Virginia Fields G2G6 Pilot (702k points)
Thank you - I haven't managed to convince anyone so far :)

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