Number of Matches on a Segment (or TG)

A Segment-ology TIDBIT

Segments from Ancestors with large families will generally have more Matches (in general, the larger the families, the more cousins you have). Segments from more distant Ancestors will generally have more Matches (in general, the more distant the ancestor, the more cousins you have). Segments from Ancestors in Colonial America will generally have more Matches (in general, more Americans have taken the DNA tests). Segments from endogamous Ancestors will have more Matches (because of endogamy, there is more matching DNA).


22B Segment-ology: Number of Matches on a Segment (or TG) TIDBIT by Jim Bartlett 20170101


10 thoughts on “Number of Matches on a Segment (or TG)

  1. Jim,

    Quick question for you! Do you have any suggestions or guidelines on what makes for a solid TG when you have only 3 individuals who match on a shared segment? If a brother and a sister both match a very distant cousin on a shared segment, does that make for as strong of a TG as and parent and child matching a distant cousin on a shared segment? I realize that the more matches (more than 3) you have in a TG the stronger that is for tracing to the shared ancestor and possibly walking the shared segment back with additional range of “cousins” who test and share the same segment. In cases where you only have 3 people in the TG, is there a vary degree of reliability that you have a solid TG depending upon the familial relationship of the testers?



    • Tim; since a parent and child or two siblings all carry very large amounts of atDNA they are much WEAKER in a TG. So much so that we count two siblings as only one leg (essentially the same person) in a TG. What gives a TG strength is the fact that three widely separated cousins match. Widely separated people generally don’t match – the fact that three of them do, makes the TG strong.


      • Jim,
        Thanks for responding! This is what I was thinking, but wanted your expert confirmation.


  2. Jim, Thanks for this information. I will try my best to digest this as best as I can as it is foreign to me! However, I am willing to learn. Good to hear from you again. I am making good progress on my paternal side but still very slow on my maternal side (the side where your son matches me). I have found some Moody’s in Canada who have relatives in Delaware. Need to determine if they are connected to the Moody’s from Pennsylvania. Not getting anywhere with the Smith’s. I’m on a medical leave for the next two months so I plan on spending most of it on learning more about my ability to search my ancestry.

    Happy New Year!

    John Guilbert A935219


  3. Thank you! Am trying to deal with early colonial ancestors who had large families and married cousins (sometime many generations later cousins). This really helps.


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