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Old 30th August 2017, 04:25 PM
MoberlyDrake MoberlyDrake is offline
mtDNA: T2b5 | Y-DNA: J-M172
 
Join Date: May 2010
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Triangulation Question - Why Such Small Segments?

I have two instances where I have identified large segments as coming from a particular line in which interested. For instance I have one case where 2 matches descend from the same ancestral couple, one sharing 53 cM and one 45 on the same segment, with another person with the same surname, but exact relationship unknown, sharing 23 cM. I get excited thinking I have a great opportunity for a triangulation. Then I look at Gedmatch at at my spreadsheet which contains data from both 23andMe and FTDNA and there plenty of matches on this segment, but almost every one of them is between 7 and 10 cM long.

The same is true for a couple of other segments I have identified as coming from this same line. Why are the segments always so small except when the match is a descendant of my mother's great-grandfather or great-great-grandparents??? I'm trying to identify the unknown 3rd great-grandparents. As far as I can tell, they were descended from families who arrived in America before 1700 from the UK.
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