Jigsaw Puzzles
Our genetic genealogy is very much like a jigsaw puzzle. Our Ancestors and our DNA segments are both pieces of a large jigsaw picture (ourselves). Soon after the moment of conception – when sperm meets egg – our DNA segments and crossover points are determined. And, of course, our Ancestors, each with 2 biological parents, are determined. There may be lots we don’t know, but those configurations (DNA and Ancestors) are fixed – waiting for us to discover them. Just like a box of jigsaw puzzle pieces, all the pieces are there – and they only go together one way (like our DNA segments and our Ancestors).
Now think about our DNA Matches – perhaps 100,000 of them – as we open our list… The overarching concept is that a Match sharing at least 15cM with us is always a true (Identical By Descent or IBD) relative; and over half of the remaining Matches will also be IBD and a true relative. Of course, some of these Match-relatives will be distant cousins.
Based on my deep dive with Pro Tools, I’m now convinced at least 20% of my DNA Matches at Ancestry are relatives within a genealogy time-frame. I’ll go out on a limb and say 8C or closer!.
So, to the point of this blog post… 20,000 of my 100,000 Matches are probably 8C or closer. Each one of them is a jigsaw puzzle piece. Each one interlocks with me (sometimes in multiple ways) and very often with other Matches (look at *their* Shared Match list). In many cases they form interlocking relationships with each other, from siblings to parent/child to 1C and 2C and 3C interrelationships. Just like a jigsaw puzzle. Some will be like the jigsaw lake, or forest, or barn or road – all of which “clumps” of the puzzle will eventually integrate – only one way – into the grand picture….
With Pro Tools’ new Sort feature (the Shared Matches’ *close to distant* Sort), it’s a whole lot easier to form small branches. Think of it this way…. You have 1,000 Matches, and you can easily find links that result in 500 pairs…. In a flash, you’ve cut your workload in half. And as you form larger clumps of Matches – all of your Matches in that clump must lead back to you! Put another way, look at the clump and see where all of your Matches have a Common Ancestral line – out of the clump and directly into your Tree – somehow…
The jigsaw puzzles:
- The Ancestors must interlock in pairs and form an entire “Tree” jigsaw picture>
- The DNA segments must array adjacently and form a Chromosome Map picture
- Our Matches will interlock with us; each other; and our Ancestor Tree.
[22CV] Segment-ology: Pro Tools Part 14: Jigsaw Puzzles by Jim Bartlett 20241124
segment-ology 
I’ve been reading your ProTools articles with great interest. I’ve looked at segments on-an-off for a few years, so I’m familiar with all of the terms.. Here is a MyHeritage “study” I carried out recently. I found a match of interest that possibly leads back to a 7X or 8X great-grandparent. Scot is 1 generation older than me, and our match is just 10.4 cM. Beside the common surname (about 1750 or earlier) I found we share 751 DNA Matches. Even more intriguing is how many triangulate. I downloaded the segment information for those to a spreadsheet, and stopped when I hit 100 matches. The effort just wore me down, and I wanted to get input on my method. The greatest match amount in the bunch is 21.7 cM. All are on Chr 11. Three matches have a segment greater than the 15 cM IBD threshold you mention in this article. Besides looking at as many trees as I can find, do you have any suggestions? Above all, is this a reasonable pursuit as far as the segments? Thank you,Ed
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Ed, A good example – right on the fringe of what I think is a reasonable limit to genetic genealogy (without a LOT of extra work). My go-to method is to look at the Trees,,,. Sorry, In theory, every Match in a TG will share an Ancestor on one path back up your Ancestry. This path is rarely all one surname line. I’ve been lucky a few times to have a TG that was on the same SURNAME line for 4 or 5 generations – so 4C to 8C would have that surname in their Tree. If the TG path is an all female line or one with lots of male-female zigzags then we won’t have a single surname for the whole path. Well…. most of the Matches should, eventually, go back to a CA, but for 7X and 8X grandparents that’s a long way back to trace all of the lines.
The only other option I know of is Clustering (Shared Match Clusters *tend* to form on individual Ancestors) which can also be done at MyHeritage, based on closest cMs to each Match (just like Pro Tools). In this case, you use a Match’s closest Shared Matches to build their Tree back, gradually adding more and more Matches. “Their” CA should be on their path back to their CA with you. In some cases this may be easier; in some cases, not. Please let me (actually all of us) know if you figure out a good method that works – even just some of the time. Jim
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I really appreciated this blog post, and others you have written on Pro-Tools. In fact prior to reading your various posts, I wasn’t bothered about subscribing to Pro-Tools. Since then I have found that cracks are appearing in my brickwalls. I hadn’t looked into the sort feature for Pro-Tools until reading this post – so thanks for sharing your thoughts.
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Kerrie, Thanks for the feedback. I’ve found several new Floating Branches with Protools. At first I was worried that they may have a Common Ancestor who is not, in fact, tied to my Tree. But then I realized that they were all *my* Matches – so in theory they should tie in somewhere. Usually with enough digging into their Tree (almost always on their female lines), I can find the link. Sometimes I put it into the “comebacklater” pile…. Jim
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I got lost at the 4th paragraph. I am under the impression that a much higher percentage of my DNA matches are 8C or closer. I don’t know how to quantify that percentage. I didn’t follow your argument about doubling the matches.
I have identified about 2400 DNA matches to a spot in my tree. The larger part of them are from Ancestry where I presently have 72118 matches of which 3006 are 4th cousin or closer. I can’t get a count of those over 15 cM.
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Greg – don’t lose any sleep over it. In para 5 I was trying to make a point that connecting individual jigsaw pieces helps – just like linking a parent/child or 2 siblings with Pro Tools – it starts building a clump… I do have almost 100,000 Matches at Ancestry, and I’ve got about 8,000 linked into my Tree (well indentified to a path – I’m now going through the whole list and typing them into my Tree) – I think that will more than double with Pro Tools. I have saved Matches down to 6cM. I do believe many of them are IBD relationships, but are probably beyond my 8 cousin level. Back when I could easily tally the numbers I had 4% over 20cM; 8% 15-20cM; 20% 10-14.9cM; 9% at 9cM; 12% at 8cM; 17% at 7cM; 30% at 6cM. FYI. Jim
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