As I look at ThruLines Matches under 15cM, roughly half of them have a Side (Maternal or Paternal) which is different from the Side of the Common Ancestor proposed. What’s up?
AncestryDNA has determined a “side” (Maternal or Paternal) for most of my Matches. Pretty slick! And very helpful!! For above-20cM Matches they appear to be fairly accurate. This is despite the fact that all of my Paternal and half my Maternal Ancestor were mostly from Colonial Virginia. I was expecting a lot of Matches to be “Both”, but relatively few are. The bulk of my Matches are in the Maternal and Paternal categories. And below 15cM, the Maternal or Paternal “sides” are not aligning with the “side” for many of the ThruLines Common Ancestors. Side note: it appears that Ancestry is now only reporting one ThruLines Common Ancestor per Match – they used to report two or three if they found them….
What are the possibilities?
1. The AncestryDNA “sides” may be incorrect. I’d like to think (hope?) that the science behind them is valid and that they are largely correct. Most of mine above 20cM appear to be.
2. The ThruLines may be incorrect. This is a genealogy area (not DNA). With my 50 years of genealogy research, I already know many of the descendants of my Ancestors, and I run a check (not-GPS-comprehensive) on each ThruLines reported. I used to spot about 5% with errors (some of which were easily fixed), but now there are more and more as AncestryDNA appears to have become fairly aggressive at finding Common Ancestors. It appears they have loosened up the algorithms to allow “close” name variants and “close” dates, resulting in more false results. But even with the ThruLines I review and accept the Common Ancestor from a genealogy point of view, there are roughly half which don’t agree with the “side”.
We cannot have it both ways… or can we?
When AncestryDNA determines a Maternal “side”, does that guarantee that 100% of the Match’s atDNA can only be on my Maternal side? I really think that is absurd! Particularly when you consider most of my Ancestry is from Colonial Virginia. Surely my Colonial Virginia Matches could descend from Ancestors who would be on both sides of my Ancestry. In fact, I have several of my own Ancestors who, due to distant pedigree collapse, are on both sides of my Tree.
I think it is entirely possible that the bulk of a Match’s atDNA could align with my Paternal or Maternal DNA, but that some of the Match’s segments could be from the other side. I’m scratching my head over whether or not this could occur half of the time.
3. Both Ways! My conclusion is that we can have it both ways! I have a colored Dot for cases with both “sides”, but I’ve decided not to let that, by itself, stand in the way of accepting a ThruLines Common Ancestor as valid.
I’m curious about your overall experience and observations about conflicting “sides”. You are encouraged to add your insights in the comments.
[35AA] Segment-ology: AncestryDNA Side vs ThruLines Side by Jim Bartlett 20240213
segment-ology 