Save the Clues!

A Segment-ology TIDBIT

In genealogy if we look for Thomas BARTLETT in the census and find three entries with that name, we don’t discard them all if we cannot immediately figure it out. We record them all and look for more evidence. The same concept applies to DNA. Record all the Common Ancestors you find with a Match. Even if the Match is a 2nd cousin (2C), she may also be a 5C or 8C on a different line. One of her shared segments may go back to that more distant ancestor – it’s happened to me! Don’t disregard a “pile up” of shared segments which Triangulate (just because they may be from a very distant ancestor). Science tells us that some of those 7-20cM shared segments will be with closer cousins – it’s happened to me, often. Don’t disregard a distant cousinship beyond 5C with a Common Ancestor. Save the clues. As new Matches come in, you may find supporting evidence for that CA in the TG – it’s happened to me. I have 11 out of 35 Matches, on one TG with the same 7G grandparents (some of them are 6C and 7C, the rest are 8C).

 

[22E] Segment-ology: Save the Clues TIDBIT by Jim Bartlett 20170103

7 thoughts on “Save the Clues!

  1. Re; ” Even if the Match is a 2nd cousin (2C), she may also be a 5C or 8C on a different line. One of her shared segments may go back to that more distant ancestor – it’s happened to me!” Excellent advice. It’s happened to me as well.
    Lou

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  2. I have a huge pile-up.. I haven’t counted, but well over 500-1000+ people. I had been discarding it because I couldn’t make heads nor tails out of it, Once I started conquering my Colonial Soup, it was becoming clear that I had three 7GGFs who were brothers on three different lines making my 8GGF (their father) the likely common ancestor (and probable cause of the pileup.) The fun part will be trying to place each segment on the correct line (the pileup crosses many segments)

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    • Clark,
      I’d be very suspicious of such a pile-up. Please read my blogpost about pile-ups to see if you have a good one or a bad one. I’ve got two, similar to your description, that are very BAD.

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      • Thanks Jim. I have read it before, and these massive (i didn’t say large) pileups are in the 8-10cM range and also hover around the centromere on Chr19. I still consider the majority as bogus, but there are a few that seem good or that I would consider good if the pileup wasn’t all around them. By bumping the cM to 15, I tend to weed out the pileup noise.

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      • P.s., while not the best indicator of a pileup, I’ve noticed the SNPs are rounded to the nearest 100 in many cases:
        20190111  35756431  9.74  1500 
        20190111  35756431  9.74  1500 
        20190111  35756431  9.74  1500 
        20190111  35756431  9.74  1500 
        20190111  35756431  9.74  1500 
        20190111  35756431  9.74  1500 
        20190111  35756431  9.74  1500 
        20190111  35756431  9.74  1500 
        20190111  35756431  9.74  1500   <–pileup?
        20190111  35756431  9.74  1500 
        20190111  35756431  9.74  1500 
        20190111  35756431  9.74  1500 
        20190111  36206662  10.33  1600 
        20190111  36707544  10.82  1700 
        20875787  35756431  9.10  1400 
        20875787  35756431  9.10  1400 
        20875787  35756431  9.10  1400 
        20875787  35756431  9.10  1400 
        20875787  35756431  9.10  1400 
        34103313  46393368  16.12  3184  <–Good matches?
        38702129  50085313  16.48  2861  <–Good matches?
        38921659  45801296  9.10  1684  <–Good matches? 
        38921659  46127576  9.45  1784   <–Good matches?
        38921659  53030647  22.83  3514   <–Good matches?
        38921659  55971694  31.19  4447   <–Good matches?
        39742673  50085313  15.12  2561   <–Good matches?
        41311232  54350202  21.91  3314   <–Good matches?

        Hard to say without further investigation, but the "exact identicalness" raises red flags for me.

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      • Clark, As I indicated in my Pile-Up post, a very narrow, very tall, group is usually a BAD pile up. Have you compared any of these to each other? That is an important step. If they do not match each other, they are IBC.

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