This post is intended to get you to think about the possibilities in your own Tree – it is not about the term NPE (there are many variations); and it is not about the historical percentage (there are NPEs, but not many good studies on the NPE percentage). For this blog, I’m using NPE to mean an Ancestor who by most accounts is in our Tree, but it turns out that “Ancestor” is not our biological Ancestor.

Three assumptions for this post (in order to get to the thought process):

1. NPE is a paper-trail/genealogy Ancestor, who is not the biological Ancestor.

2. The rate is 2% – there are many studies (cf: https://isogg.org/wiki/Non-paternity_event )

3. I’m going to count each “box” in our Tree as an Ancestor (recognizing that there may be some Pedigree Collapse and/or Endogamy)

The mumber of our Ancestors doubles every generation. At 8 generations back we have 256 Ancestors at that generation and 510 total Ancestors all together. At a 2% NPE rate overall, that would mean about 10 of our Ancestors were NPEs. If you read the ISOGG article above, you’ll find a slew of reasons for NPE (in addition to infidelity). As a genealogist with many Colonial Ancestors, I believe the instance of one or both parents dying in those times, and someone else raising the orphaned children as their own (with no paperwork) was more prevalent than we know. And probably many other variations…

So if the paper-trail doesn’t help, how would we ever know? I think our DNA Matches can sometimes give us a clue.

From my experience tracking Matches (see: https://segmentology.org/2021/12/19/segmentology-common-ancestor-spreadsheet/ ), I can tell you there is a clear correlation between family size and number of DNA Matches – the larger the number of surviving children (with families of their own) the more DNA Matches we’ll have. And the obverse: with a “skinny” family of only one child, we get no cousins, and if there are two children (one is our Ancestor), any Matches would descend from the other child, and there would be far fewer Matches. Some other factors may also come into play, such as distance back to the Ancestor and recent immigration, so we must take those into consideration as well.

So here are two scenarios to think about:

1. A large family with relatively few descendant Matches – maybe one or both of the “parents” are NPEs.

2. A Surname comes up repeatedly in Matches – say within a Shared Match Cluster, or a Triangulated DNA Group. I now have two of these – in each case virtually all of the Matches are from the same Tree. Clearly, I should descend from this Surname – I just need to find out how (and if it involves an NPE or a Brick Wall).

As I said at the top of this post, this is just to get us all to think – to keep an open mind – to follow the DNA signals – and to understand that we probably have some NPEs in our Tree. Watch for the clues….

[30B] Segment-ology: How Many NPEs Do You Have? – by Jim Bartlett 20220325