DNA - has somebody not been telling the truth?

Question

Having recently got both my and my wife's DNA tested, I am faced with an inconsistency on my wife's data. Her great grandfather as far as she knew was German and all things being equal (which of course they aren't) she would have some 12.5% of DNA which would normally, due to the company's previous experience, be tagged 'German'. There is no trace of 'German' DNA and in its place is a completely unexpected 5% of European Jewish DNA. Her sister who also recently had her DNA tested shows the same broad traits. Her great grandfather's lineage has been traced on paper back to the sixteenth century with no known digression from the German Lutheran tradition.

The only conclusion I can draw is that her great grandfather wasn't her great grandfather at all! It is not possible to say that the Jewish DNA replaced it as it may have sneaked in some other way but there is nothing obvious.

Unfortunately there is a lack of people to use as a control. A second cousin with ostensibly the same great grandfather checks out with 23% German but this is clouded due to the fact that separately she had a German grandmother. She displays not even a trace of Jewish DNA.

Am I reading too much into this or are my conclusions likely to be broadly correct?

Comments

Jews could also be German.  Germans could also be Jews.  Germans who were Jews may not always have  known they were Jewish, or may have suppressed that knowledge.  Being Jewish was not exactly seen as a good thing for much of European history.

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But in that case her second cousin should have it too. I can accept that there might be a trace but I would have thought 5% was more than that. And where has the well-documented German ancestry gone?

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One thing that has been stated is that basically, the DNA is distributed in a "shot-gun", that is to say it is "unevenly" distributed, as seen in cases of even identical twins (other than the diploid twins) and in many cases among siblings

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I believe it has been said on G2G that most of the ethnicity dna stuff is for "entertainment" and you should not necessarily take is as 100%  truth.  It also can depend on the size of the "pool" being checked against.

IF you have documents with the trail, I would believe the documents.  (If I took a dna test and it told me I was part Egyptian, I would laugh and throw that test result in the garbage. Similarly if it told me I was whatever % Native American, or Pakistani, or Greek.)

Likewise, if my sibling and I took dna tests, the results of each could just as easily come back showing us as cousins, as it would full siblings.  Or it might show me as the child of our parents, and my sibling as the child only of our father.    Neither type of result is reflective of the reality that my mother conceived and gave birth to us both.  Your wife's cousin would not have inherited the same amount of dna from her  parents, as did your wife from hers.  The % from each parent is diluted by the generations, so the chance of them matching is smaller with each generation.

I have 2nd cousins who are related on my paternal line. The amount of dna they inherited from our common ancestor will not be the same % as was passed down to me.  There are also chances that a test result might show us as barely related, due to the influx of dna from their mother's side.  I believe the paper trail, and that they look like their father, who looks like his brother, whose son looks  like him, whose children look like him.  Likewise on my maternal line.

Now, before I make a complete fool of myself (as though I haven't already done so), I shall step away and leave this to the likes of Edison and the other dna mavens of Wikitree.  :)

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Melanie, your summation / explanation is well presented. Thank you. It was eloquent.

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To reiterate one of the points Melanie made: FTDNA says I'm 77% British Isles, 20% East Europe, 1% Scandinavian, and 2% other. MyHeritage, using the exact same DNA data, says I am 42% Scandinavian, 32% East European, 22% Irish/Scottish/Welsh, and 4% other. And ancestry.com says I'm 43% England/Wales, 31% Germanic Europe, 11% Norway, 8% Baltics, 4% Ireland/Scotland, and 3% Eastern Europe. So I'm anywhere between 11% and 32% East European, 22% and 77% British Isles, 1% and 42% Scandinavian, and 0% and 31% German. Based on paper trails, I am actually roughly 45% German, 15% Lithuanian/Polish, and 40% British (with a bit of Huguenot French thrown in). So, all in all I find the ethnicity estimates to be useless for genealogical purposes.

Answer 1

This article explains why someone may have unexpected ethinicity results https://support.ancestry.co.uk/s/article/Unexpected-Ethnicity-Results

Comments

Thanks for sharing that article Samantha, it echoes what I was just about to write:

Ethnicity estimation is still a work in progress.

Ethnicity estimation is a challenge that scientists around the world are still working on. We provide the best estimate possible given our current data and knowledge, but we’re also working hard to improve the precision of your ethnicity estimate.

Each time we tweak our data, it’s possible that your ethnicity estimate will evolve along with our understanding of DNA science.

My father and I, according to our DNA tests share 1/2 of our DNA.  However, our ancestry doesn't just have different percentages, we have different ethnicities.  I have Balkan DNA that he or my mother do not have.  How can this be?

We took out tests more than 10 years apart.  I suspect that while they have refined the test since I was tested and his test is more "up to date" on the ethnicity, they didn't bother to change mine because it tends to upset people when you tell them that they no longer match the DNA ethnicity that they have accepted and internalized.

My wife has a tiny bit of known East Asian DNA and her FtDNA results show it as Native American.  Surely it is an older marker and they have allocated it incorrectly.  In time they will probably update it.

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So the net result is that it should not be taken too seriously. My wife's great grandmother is off the hook... Thanks everybody!