A Segment-ology TIDBIT
I made a spreadsheet of my 1,820 ThruLine Matches – to track and analyze them all. I found 86 were questionable (some of those 86 were clearly wrong, and others were iffy – I just didn’t have the information (or time) to sort it out. 86 is roughly 5% of the total, which means I agreed with 95% of my ThruLine Matches. Note a few of my Matches are double counted because they shared more than one Common Ancestor with me.
A high percentage of ThruLine Matches were good, giving me confidence in this tool.
Of my ThruLine Matches, 145 of them had uploaded to GEDmatch (or tested at other companies). I found one of the 145 (1.5%) had a false Shared Segment with me – it didn’t match a Triangulated Group on either side. I also found that 15 of these Matches (10%) with segment info had TG segments with me which were on a different one of my grandparents than the ThruLine Common Ancestor. This is not necessarily an error by ThruLines (the Match is very likely still a genealogy cousin on the ThruLines Common Ancestor), but in each case the DNA Shared Segment indicated we should have another Common Ancestor on a line from one of my other grandparents. Most of the 15 Matches were on the wrong side – the ThruLines Common Ancestor was on one side, and the Shared DNA Segment was on the other side.
So, from this small sample, about 10% of the ThruLines Common Ancestors may be misleading from a genetic (or chromosome mapping) point of view.
[22AK] Segment-ology: A Few ThruLines Are False, and Some are Misleading TIDBIT by Jim Bartlett 20190729e