30 March 2017

Why Are Your DNA Ethnicity Results Unexpected: Misattributed Parentage

Misattributed parentage, paternity and/or maternity, is an even more PC term for NPE (non-paternal event), an umbrella term for undocumented name change and adoption, illegitimacy, bastardy, etc.

NPEs are one factor to be taken into account in examining ethnic ancestry results of a DNA test. It's highly unlikely your genetic and genealogical family trees are the same, even for those occupying high office.

What ever you call it studies suggest the rate of NPEs is in the range 1-2% per meiosis (meaning for each child).

Back 10 generations, the timeframe now given by Living DNA as appropriate for the results of their sub-regional results, we all descend from a total of 1+2+4+8+16+32+64+128+256+512, or 1,023 meiosis.

At a rate of 1% meiosis that's an average 10.23 NPE events in your family tree; at 2% 20.46 NPE events.

On average half of them will be in the most distant generation. If the misattributed partner is from the same group of founders the ethnic ancestry will be unaffected.

In case you think that doesn't apply to you, at 1% the probability of no NPEs in 10 generations is
0.99^(512+256+128+64+32+16+8+4+2+1) = 0.99^1023 = 0.000034.

That's only 34 out of 1 million people without any NPEs in the 10 generations. At 2% it's one in a billion. To be clear, that's the probability for all ancestors not for a single line such as the father's father's father's ... At 1% (2%) NPE rate there's a 90% (82%) probability the paternal line is correct for 10 generations and the genetics follows the surname.

NPEs are not the only reason you may have unexpected results from any DNA ethnic ancestry test. Stay tuned.

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