17 thoughts on “Insights into cM Patterns”

1. Jim – You say “I can only dream of how many ThruLines I’d get at the 7C and 8C levels.” As you likely know, you can fool AncestryDNA into providing some of these by making yourself a sibling to your parent (or grandparent) in the tree you are linked on. What had been your 6th GGPs are now your 5th GGPs and visible. I’m not sure how many would show up if you are now two or three generations older than your actual 7Cs – but I do it every few years and I find some interesting and real 7Cs. I posted this on Facebook years ago and three or four people thought it was the end of the world; that at that moment someone might be looking at my tree and get the wrong data. Meh. It takes maybe 36 hours to update, and I change it back a few days later.

   LikeLiked by 1 person

   Reply ↓

   • Rich, I do use that tip – several times a year. And like you, I try to whiz through the new ThruLines (and put them in my spreadsheet), so that I can revert to the standard way quickly. Note that ThruLines limit is 6C level on both parties. So what you can get at the parent level is only 6C1R. You look like 7 generations back (but the CA is actually 8 generations back); and the Match has to be within 7 generations of that same, fairly distant, CA. It does add some true Matches to our list, but if Ancestry up the level to 7C for ThruLines, we’d get a LOT more. In the meantime, we do what we can. Jim

     LikeLike

     Reply ↓

2. Jim, WOW is right. Very impressive. I’m imagine you are shooting for 10000 matches now to make statistics easy. I was wondering if you have correlated all these matches somehow with your TG’s and if any insights resulted? I know much of this match data is from Ancestry, but with all the overlapping matches in multiple databases the segments often seem identifiable.

   LikeLiked by 1 person

   Reply ↓

   • pdtbill, When I add in my data for other companies (not really apples to apples because of Timber), I have over 10,000. My goal was to confirm relationships with 10% of my Matches at AncestryDNA, which is hard (but ProTools are helping – not enough time). And yes, I’ve determined the TG with 1,065 AncestryDNA Matches, but not all of those Matches include MRCAs.
     I am working on an improved/streamlined Walk The Clusters Back (WTCB) version, which lets me impute known TGs in a Cluster to other Matches (working down to 20cM Matches). This TGID then carries over to the data set in this post. My “expectation” there is that the TGs will be distributed, roughly, equally by generation. In other words, if I round my 372 TGs up to 400 TGs, I’d have 100 TGs “flowing” through each of my grandparents (with Matches at nominal 1C level. Note: “flowing through” is not the same as “originating at”. Then 50 at each G grandparent; 25 per 2XG grandparent, etc. to about 1 TG for each 7xG grandparent at 7C level. In other words at the 6C level (where I have the most Matches), I would expect to see about 3 TGs (or actually 6 TGs for each couple). So if you track the TGs in the Common Ancestor spreadsheet (as I do), don’t expect them all to be the same in each family, but do expect a small number of them, probably confined to different branches in each 5xG grandparent/couple family.
     I check GEDmatch every week for new Matches from AncestryDNA kits… AND I put the TGID in the new Notes column at GEDmatch to track the ones I’ve done. Jim

     LikeLike

     Reply ↓

     • Great, thank you. I’m always trying to learn & follow your lead here.

       LikeLiked by 1 person

3. Jim o ricevuto un altra corrispondenza di condiviso di 13.9cN con due segmenti il più grande triangolato con altri di 7,1cM che si aggiunge al gruppo Gia esistente di 18 match piu io sul chromosome16 e dai suoi cognomi genitori mi pare che sia tra rom e misti rim

   LikeLike

   Reply ↓

   • Kevin, It looks like you are making good progress with this TG on Chr 16. It’s now time to transition to genealogy research to try to determine how the TG Matches all interrlate to each other – to find your Common Ancestor. Jim

     LikeLike

     Reply ↓

     • Jim mi sai spiegare che vuol dire questo messaggio dal team di myheritage sul fatto che ho queste corrispondenze che ti parlo sempre

       LikeLike

     • Kevin, It’s all about the power of autosomal DNA to find distant cousins to you. Generally, the more distant they are the smaller the shared cMs. You should use DNA Painter, and plug in the small cM amount and see the wide range of relationship possibilities. These small segment Matches may well be from your Ancestors well beyond a genealogy timeframe. The DNA gives you Matches and their cMs, which provide a rough range of possible relations. The next step is to use genealogy to figure out how you are realted to the Matches. Jim

       LikeLike

     • Jim.come posso vedere se un tg triangolato viene da un figlio ho dei figli dei antenati o antenato?

       LikeLike

     • Kevin – only with genealogy – finding a Common Ancestor with each MAtch. The TG segment of DNA you share with each Match was present in one of your parents, one of your grandparents, one of your Great grandparents, etc back to the Common Ancestor you have with that Match. You may have different Common Ancestors with different Matches, but they must all be along one path to the most distant CA. In other words with the Matches in a TG, you may be a 4C with one, and 5C with another and 6C with a different Match – but the CAs would be along one path. As I explained in a recent post, when you get down to 15cM or below, that amount of DNA can be shared with a wide array of different relationships from 4C on back. For each of your Matches in the TG, you should look up the shared cM using DNA Painter to see the wide array of possibilities. That’s all the DNA can do! The rest has to be genealogy work – looking at Trees and records. Jim

       LikeLike

4. Thank you for this explanation … I could feel “bits and pieces” of that story lurking in all we speak to in genetic genealogy but you have explained it in a way that helps make sense of it all to me !!! Thank you.

   LikeLiked by 1 person

   Reply ↓

   • John, Thanks for your feedback. Jim

     LikeLike

     Reply ↓

5. Jim, some amazing analysis here. Well done.

   LikeLiked by 1 person

   Reply ↓

   • Jean, Thank you! Jim

     LikeLike

     Reply ↓

6. If I had to describe what one of worst nightmare situations would be it would be having to live with this man.

   LikeLike

   Reply ↓

   • Linda, Well… my wife is a PhD scientist and taught me a lot about DNA/biology. Her work with cancer researchers had a parallel with this post… be sure you understand when some data is missing (for a variety of reasons), because it skews the averages. I see many genetic genealogists trying to “sharpen a marshmallow” – trying to pinpoint a relationship using shared cMs… we can get a range, but not “the” relationsip with cMs. At that point we have to include genealogy in the analysis. Jim

     LikeLiked by 1 person

     Reply ↓

This site uses Akismet to reduce spam. Learn how your comment data is processed.