Friday, August 18, 2017

Are Ethnicity Percentages and Ancestry Calculators from DNA Tests Accurate?

The media has blasted headlines this week that show an incredible ignorance of DNA testing for ethnic percentages.  One, which could have been pulled out of a 1980s tabloid for its ridiculousness, screeched, "Neo-Nazis are taking genetic tests and are deeply upset by the results!"

Neither of the two writers delved too deeply into the subject, and that is because shorthand reporting is easier.  As we've posted, again and again, most of the three major DNA testing sites disclose quite openly that their science is far from perfect.  For example, that if one is German, French, Dutch, Belgian, Austrian, or Swiss, that they cannot discern your ancestry 92% of the time.  (With the US having more people of German ancestry than even English or Irish -- that's a big deal).

In fact, it's quite common for someone taking a test from three different websites to receive three different results!  And as the post beneath this one shows, trying the 40 or so other "ethnicity calculators" available for free on Gedmatch produced...40 different results.

As I often say: if 5 different scales produced 5 (vastly different) weights, you would know that at least four of 'em don't work!  :-)

Anyway, for those looking for perspective, we shouldn't highlight the bad, so we've decided to highlight the good -- or the excellent, rather.

One of the best posts we have seen on the topic comes courtesy of a blog called The Legal Genealogist.  It's called, "Those Percentages If You Must" -- and is a Must Read for people curious about whether ancestry calculations from DNA tests are accurate.

It first, rather hilariously, goes into the various myths and misperceptions about DNA and human history.  Concepts like, "black Irish" or "I have some Native American in me."  Concepts that plague the world of pop-DNA-testing.

After it goes through the science (in easy to understand terms), it reveals what I have posted here time and time again:

DNA testing IS GREAT and REMARKABLY PRECISE for finding you cousins.  It CAN tell you if you are a third-cousin, once-removed (with that kind of precision).  If you don't know your heritage, and that cousin is, for example, 100% Native American -- then it follows that you too have a pair of Native American great-great-great grandparents.

DNA testing IS NOT good at ethnicity percentages and ethnic calculation.  As if anything could be so precise as to tell you that you are "4.2% Jewish."  The science is still just not ready for prime time, and many underrepresented populations, even in Europe, still confound the tests.

(As an aside, ancestry calculators should all produce nice and even results when people get back to the pre-travel era."  In other words, if you had 64 ancestors that were alive in 1500 AD, you should only see multiples of 1.56% chunks, right?  Since no one is half a human!)

The article succinctly concludes with:

DNA testing is a wonderful tool. It can connect us with cousins we’d have never found otherwise to help us reconstruct our family histories.

But in terms of “am I Native American?” “what tribe did I come from in Africa?” “am I 25% Irish?” No. No, no, no.  That’s the absolute weakest aspect of DNA testing. 

Indeed.  Well said.

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