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  • Big Y STR differences

    My one match's Big Y results are in, and our STR differences are 4 of 652. Is this a close match? Would this be a more accurate indicator of TMRCA than the 12-111 markers?



  • #2
    Originally posted by macp View Post
    My one match's Big Y results are in, and our STR differences are 4 of 652. Is this a close match? Would this be a more accurate indicator of TMRCA than the 12-111 markers?

    Those differences should be added to what you got originally. For example, a Y-DNA 5th cousin of mine started out as a 110/111 match for me. On the Big Y-700 he differs from me at "0 of 647" of the additional STR markers. That makes him a 757/758 match for me, or 99.868%! Not bad!

    So, it depends on how far off your match you were on your original 111 markers.

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    • #3
      Yes and No......

      Yes, in my experience 4 out of 652 is a very nice match. I have two 5ths with a GD of 3 and a 6th with a GD of 6 (on the BigY STRs only).

      But..No...
      The BigY STRs are the orphan of BigY testing. Very few people look at them seriously, at least not in the present time. As Stevo said, you need to add them to your Y111 scores as well.

      You can get much better estimates by looking at your BigY Non-Matching Variants and your Y111 mutations. Those two results are the key components.

      AFAIK, not even FTDNA uses the BigY STRs in their Discover or TIP tools.

      And while you can see your BigY STR values, you can not see the BigY STR values of your match unless he downloads and sends you his markers. So they are not very helpful in the current FTDNA report.


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      • #4
        I would also like to add that SNPs are much more important than STRs, since STRs mutate more frequently, and a number of them are infamous as fast mutators. Back in May of 2006, when I got my initial Y-37 results, STRs were pretty much it. People were doing all they could with them, but there was a lot of fantasy/sci-fi creativity and speculation involved, as well as some rank stupidism (I prefer "stupidism" to "stupidity" in this context, since it implies a philosophical approach that was prevalent at the time). This was especially the case since the ancient DNA revolution had not yet taken place.

        One can have fairly close STR matches who do not share one's terminal SNP. One can have STR matches a little farther away who do. Bet on the SNPs.

        The Big Y-700 is a Godsend. It really tells the tale, if you can get enough of your Y-DNA relatives to test (which takes some effort, and sometimes some cash).
        Last edited by Stevo; 8 January 2023, 06:31 PM.

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        • #5
          Don't use the STRs for determining closeness of a match, use the SNPs. If this person is a close match then find what terminal SNP you are determined to share with them in the Big Y section then use the Discover Haplogroups tool to find the estimated age of the particular branch. The age estimate is always subject to change so check back from time to time.

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          • #6
            Originally posted by mattn View Post
            Don't use the STRs for determining closeness of a match, use the SNPs. If this person is a close match then find what terminal SNP you are determined to share with them in the Big Y section then use the Discover Haplogroups tool to find the estimated age of the particular branch. The age estimate is always subject to change so check back from time to time.
            I don't quite understand, as our terminal SNP dates to about 750 BCE.

            EDIT: I'm not sure what constitutes a close match, but this man matches me at 2 of 25, 4 of 37, 5 of 67 and 7 of 111. We don't match on 12.

            Last edited by macp; 9 January 2023, 12:20 PM.

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            • #7
              Provide a screenshot of your "Block Tree" making sure no peoples names are shown. Or join a project and have an administrator look at your results for you.

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              • #8
                Originally posted by macp View Post

                I don't quite understand, as our terminal SNP dates to about 750 BCE.

                EDIT: I'm not sure what constitutes a close match, but this man matches me at 2 of 25, 4 of 37, 5 of 67 and 7 of 111. We don't match on 12.

                Honestly, that's not an especially close match, not in genealogical terms, anyway. If your MRCA was born about 750 BC, you two are not close Y-DNA relatives. That info is still valuable, however, since you are closer to each other by far than to most other men, and it can be used to construct a useful phylogenetic tree showing the origin of your own Y-DNA line.

                Hope I'm not boring you, but I'm going to post a graphic I made for my own line under R1b-BY168, which dates back to about 550 BC. My kit number is one of those under FGC36981 in the bottom middle of the graphic. I just wanted to show you how things might pan out for you under a SNP dated that far back. My very closest genealogical matches are all under FGC36982. All those under FGC36974 share my surname.

                R1b-BY168 descendant tree.jpg
                Last edited by Stevo; 11 January 2023, 02:20 PM.

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                • #9
                  Originally posted by Stevo View Post

                  Honestly, that's not an especially close match, not in genealogical terms, anyway. If your MRCA was born about 750 BC, you two are not close Y-DNA relatives. That info is still valuable, however, since you are closer to each other by far than to most other men, and it can be used to construct a useful phylogenetic tree showing the origin of your own Y-DNA line.
                  I have several slightly closer matches, all with the same surname or variation of it as "mine" (not really my name; I'm descended from an NPE), and our most recent common ancestors are 7-9 generations ago. If these matches took a Y700 test, would my terminal SNP change and match theirs? I'm completely confused.

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                  • #10
                    Originally posted by macp View Post

                    I have several slightly closer matches, all with the same surname or variation of it as "mine" (not really my name; I'm descended from an NPE), and our most recent common ancestors are 7-9 generations ago. If these matches took a Y700 test, would my terminal SNP change and match theirs? I'm completely confused.
                    That is possible, if a SNP turns up further downstream that you share with one or more of them.

                    For example, as a result of my initial Big Y-500 test, I got the terminal SNP R1b-FGC36974. Then a fifth cousin of mine also did the Big Y-500. He and I both went to R1b-FGC36982, one step downstream of FGC36974. Subsequently, another fifth cousin did the Big Y-700 when it first came out. He also landed at R1b-FGC36982. Then a second cousin of mine (we share the same Y-DNA great grandfather) did the Big Y-500. He and I went to R1b-FGC36981, one step downstream of FGC36982. Our two fifth cousins stayed at FGC36982.

                    The two of us who started it all with the Big Y-500 upgraded to the Big Y-700. Nothing changed on the terminal SNP front, but we did gain some information which has proven valuable on newly discovered SNPs upstream of FGC36974. My second cousin (the one who shares my current terminal SNP with me) has not upgraded from the Big Y-500 to the Big Y-700. We might get yet another terminal SNP further downstream of our current one if he did, since the 700 covers SNPs that the 500 did not.

                    Hope that is clear enough. The point of it all was to show that, yes, further testing of Y-DNA relatives can change your terminal SNP to reflect new knowledge.

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