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  • Predicted 2nd - 4th cousin

    On my match list, I have a 2nd - 4th predicted cousin relationship with a person who shares 69 cm with me, the longest block being 22 on chromosome 15 (the same chromosome contains another tiny block of 2.64 cm and chromosome 16 after it contains another two shared blocks of 4.74 cm & 3.3 cm respectively). I am Scottish and this person is looking for a mystery ancestor in Scotland, in an area where I have roots. Since I have an extensive family tree and know the names of at least every one of my third great grandparents and on most lines up to sixth or seventh, I was wondering if I might be able to assist the individual concerned...however since I am a complete 'newbie' to the field of genetic genealogy, I wanted to ask first if others reckon this match is genealogically significant?

    I am aware that the 'link' can often be further back in time than the predicted relationship.

    My other shared DNA with this individual - aside from the 22 cm block - mostly consists of very small blocks of around 2-4 cm.

    Thoughts?
    Last edited by Matt62; 6th November 2014, 10:04 AM.

  • #2
    Now that I'm no longer getting the "our website is down for maintenance" message I can give you a couple examples from my family.

    Example 1:

    I just confirmed that a match that I share with my mother is my third cousin. We knew about them but apparently they didn't know they had 100s of cousins in Canada.
    • Results for my mom and this individual: total cM = 84, longest block = 23
      Results for me and this individual: total cM = 59, longest block = 23


    My third cousin is related to me through my maternal grandfather's mother. These results need to be taken with a small grain of salt because apparently my maternal grandmother is also related to my cousin on a completely and yet to be discovered line. My grandmother does have a mystery line so I can't rule that one out. My mom and I share a double dose of DNA so to speak, albeit a small contribution from my grandmother's side.

    Example 2:

    A confirmed 4th cousin to me uploaded her test results and those of her father to Gedmatch. This cousin is related to me on my maternal grandmother's father's side of the family.
    • Results for me and my 4th cousin: total cM = 21, longest block = 10
      Results for me and my mom's 3rd cousin: total cM = 24.9, longest block = 13.6
      Results for my mom and her 3rd cousin: total cM = 73.6, longest block = 20.5

    Comment


    • #3
      Originally posted by andreastill.gen View Post
      Now that I'm no longer getting the "our website is down for maintenance" message I can give you a couple examples from my family.

      Example 1:

      I just confirmed that a match that I share with my mother is my third cousin. We knew about them but apparently they didn't know they had 100s of cousins in Canada.
      • Results for my mom and this individual: total cM = 84, longest block = 23
        Results for me and this individual: total cM = 59, longest block = 23


      My third cousin is related to me through my maternal grandfather's mother. These results need to be taken with a small grain of salt because apparently my maternal grandmother is also related to my cousin on a completely and yet to be discovered line. My grandmother does have a mystery line so I can't rule that one out. My mom and I share a double dose of DNA so to speak, albeit a small contribution from my grandmother's side.

      Example 2:

      A confirmed 4th cousin to me uploaded her test results and those of her father to Gedmatch. This cousin is related to me on my maternal grandmother's father's side of the family.
      • Results for me and my 4th cousin: total cM = 21, longest block = 10
        Results for me and my mom's 3rd cousin: total cM = 24.9, longest block = 13.6
        Results for my mom and her 3rd cousin: total cM = 73.6, longest block = 20.5
      Hi Andrea

      Thanks a lot, this information is very helpful for comparative purposes.

      Given that you have total cM = 59 & longest block = 23, my total cM = 69 & longest block = 22 with this individual seems broadly in the same playing field given that FTDNA predicts our relationship to be "2nd - 4th cousin". Also I should add that they are Canadian! There seems to be such a deep history connecting Scotland and Canada through migration.

      Last edited by Matt62; 6th November 2014, 12:06 PM.

      Comment


      • #4
        I would not count on this. The relationship can be a lot more remote, as far out as 8th or 9th cousin from what others have reported. In my own case, I can give two examples:

        Longest block 22, total 55
        Longest block 24, total 49

        Both of these matches are related to me on a Swiss ancestral line for which I have a very extensive tree; one is a Swiss national. The other had a Swiss ancestor who came to America in the early 18th century. I have not been able to find a traceable common ancestor for either, but in the latter instance, based on dates, it's virtually impossible for the relationship to be closer than 5th cousin.

        Originally posted by Matt62 View Post
        Hi Andrea

        Thanks a lot, this information is very helpful for comparative purposes.

        Given that you have total cM = 59 & longest block = 23, my total cM = 69 & longest block = 22 with this individual seems broadly in the same playing field given that FTDNA predicts our relationship to be "2nd - 4th cousin". Also I should add that they are Canadian! There seems to be such a deep history connecting Scotland and Canada through migration.

        Comment


        • #5
          Originally posted by NYMark View Post
          I would not count on this. The relationship can be a lot more remote, as far out as 8th or 9th cousin from what others have reported. In my own case, I can give two examples:

          Longest block 22, total 55
          Longest block 24, total 49

          Both of these matches are related to me on a Swiss ancestral line for which I have a very extensive tree; one is a Swiss national. The other had a Swiss ancestor who came to America in the early 18th century. I have not been able to find a traceable common ancestor for either, but in the latter instance, based on dates, it's virtually impossible for the relationship to be closer than 5th cousin.
          Hi Mike

          Thank you for this input! Very helpful, this is what I suspected could be a possibility as well. Comparing your matches and Andrea's, what surfaces for me is just how variable in time these inherited blocks can be.

          24 seems quite large though, does it not, for an seventh or eighth great grandparent? Wouldn't recombination have chopped that down to nearly zero? Intriguing, nevertheless and good to keep in mind.

          Comment


          • #6
            Some of these long blocks can be very persistent. This has been discussed on various threads over the years. The general consensus seems to be that FTDNA shouldn't count segments of under 5 cM. It leads to badly inflated predictions, especially when there's a significant amount of endogamy in a population. My other side is Ashkenazi Jewish, and the predictions, even with the adjustments are off typically over-optimistic in the extreme.

            In the case of the 24 cM block, I share it with both this match and her mother.

            Originally posted by Matt62 View Post
            Hi Mike

            Thank you for this input! Very helpful, this is what I suspected could be a possibility as well. Comparing your matches and Andrea's, what surfaces for me is just how variable in time these inherited blocks can be.

            24 seems quite large though, does it not, for an seventh or eighth great grandparent? Wouldn't recombination have chopped that down to nearly zero? Intriguing, nevertheless and good to keep in mind.

            Comment


            • #7
              Originally posted by Matt62 View Post

              Comparing your matches and Andrea's, what surfaces for me is just how variable in time these inherited blocks can be.
              I've come to realize this as well! I've tested both of my grandmothers and it is clear I inherited more DNA from them than my grandfathers plus I inherited more from my paternal grandmother than my maternal gandmother. I haven't yet tested my sisters or any of my 1st cousins but I'm interested to compare them just to see how different their results are.

              I also made a mistake in my first example. After my newly discovered cousin sat down and worked out the relationships it turns out her son is actually my 4th cousin, not 3rd. :-)

              Comment


              • #8
                Matt62, I thought I would add another situation and also some tips.

                There are two siblings that are predicted to be 2nd Cousin - 4th Cousins at FTDNA to an uncle. They both share 65 cM and the longest block is 21 for one and 20 for the other. One matches me at 35 cM and longest block of 11.

                Our trees go back at least 13 generations for most lines. Only a couple of lines have a brick wall at 6 generations. We have a lot of ancestors in common but I have to go back 10 generations before I can find the most recent common ancestor.

                I did triangulation and there is another person that matches them and my uncle on the same chromosome and the same segment but that person doesn't have a tree and isn't willing to share one. So I am not able to determine which specific line is the most likely one that we share the DNA on.

                In order to help yourself and to help your match you should get other close relatives of yours to order the Family Finder test. Then you can see if your match is a match to your relatives and if you all share DNA on the same segment on the same chromosome. If so and if one of your relatives is from an older generation the longest block should increase. Also have your match get other relatives to test in order to determine which side of their family the match is on. Then you can look for other matches on the same chromosome and segment in order to triangulate even more. The program at www.Genomemate.org makes triangulating a lot simpler. You can also copy and paste data from Gedmatch into Genomemate. So if someone has tested with Ancestry or 23andme and uploaded the data to Gedmatch you will be able to compare with them also.

                I hope you don't give up trying to help out your match. The two of you likely do have ancestors in common at some point in the past 6-15 generations.
                Last edited by Armando; 6th November 2014, 09:11 PM.

                Comment


                • #9
                  Originally posted by Armando View Post
                  Matt62, I thought I would add another situation and also some tips.

                  There are two siblings that are predicted to be 2nd Cousin - 4th Cousins at FTDNA to an uncle. They both share 65 cM and the longest block is 21 for one and 20 for the other. One matches me at 35 cM and longest block of 11.

                  Our trees go back at least 13 generations for most lines. Only a couple of lines have a brick wall at 6 generations. We have a lot of ancestors in common but I have to go back 10 generations before I can find the most recent common ancestor.

                  I did triangulation and there is another person that matches them and my uncle on the same chromosome and the same segment but that person doesn't have a tree and isn't willing to share one. So I am not able to determine which specific line is the most likely one that we share the DNA on.

                  In order to help yourself and to help your match you should get other close relatives of yours to order the Family Finder test. Then you can see if your match is a match to your relatives and if you all share DNA on the same segment on the same chromosome. If so and if one of your relatives is from an older generation the longest block should increase. Also have your match get other relatives to test in order to determine which side of their family the match is on. Then you can look for other matches on the same chromosome and segment in order to triangulate even more. The program at www.Genomemate.org makes triangulating a lot simpler. You can also copy and paste data from Gedmatch into Genomemate. So if someone has tested with Ancestry or 23andme and uploaded the data to Gedmatch you will be able to compare with them also.

                  I hope you don't give up trying to help out your match. The two of you likely do have ancestors in common at some point in the past 6-15 generations.
                  Oh definitely not Even if it is further back, yet within the window of possibility for discovering, I would be thrilled to find the most recent common ancestor. There is something rather attractive about embarking on an 'investigation' with another person and the idea that a block of DNA can be inherited for so long through numerous generations is fascinating to me!

                  Your example and advice are highly appreciated. I just joined gedmatch the other day and hadn't heard of genomemate, so thank you very much

                  Comment


                  • #10
                    That's great news Matt. I see too many people not interested in looking past 5 generations or don't want to try to figure out if a match is on a line that has a brick wall or NPE.

                    Comment


                    • #11
                      Originally posted by Armando View Post
                      That's great news Matt. I see too many people not interested in looking past 5 generations or don't want to try to figure out if a match is on a line that has a brick wall or NPE.
                      Must be laziness on their part! The idea that a substantial block of DNA on one chromosome could have been passed down through so many generations without being reduced to mince-meat through recombinations fascinates me and if the MRCA can be tracked down as a 7th, 8th or 9th ancestor then I think it would be well worth the effort.

                      Comment

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