My Autosomal DNA Quandary Persists

I wrote My Autosomal DNA Quandary a year ago, and my quandary still persists.

In a nutshell, my quandary is that the three autosomal test results I've taken do not match each other, and only one matches my perception of my genealogical ethnicity.

According to my genealogical research, based on the estimated origins of my 256 6th great-grandparents (I had to guess at some of them), is in these regions:

68%  British Isles
24%  Germany
1%  Holland
1%  France
6%  Unknown (perhaps some are French, or English, or Native American)

Compare that estimate with the results provided by the three autosomal DNA tests taken to date:

1)  The AncestryDNA test results:

The AncestryDNA ethnicity estimate is:

*  66% Europe West
*  18% Ireland
*  9% Great Britain
*  3% Scandinavian
*  1% Italy/Greece
* <1% Iberian Peninsula
*  <1% Pacific Islander
*  < !% Native-American

2)  The FamilyTreeDNA test results:

The FamilyTreeDNA ethnicity estimate is:

*  45% Scandinavia
*  32% Western and Central Europe
*  19% Southern Europe
*  4% British Isles

3)  The 23andMe test results are (Speculative estimate):

The 23andMe ethnicity estimate is:

*  46.7% British & Irish
*  24.7% French & German
*  1.9% Scandinavian
*  23.5% Broadly Northern European
*  1.2% Broadly Southern European
*  1.2% Broadly European
*  0.5% East Asian & Native American
*  0.1% Middle Eastern & North African
*  0.1% Unassigned

4)  As you can see, the ethnicity populations are not exactly the same between the three test companies.  

*  If you combine British and Irish, then 23andMe says I'm 46.7%, AncestryDNA says 27%, and FamilyTreeDNA says 4%.  [Compared to 68% from genealogy research.]

*  FamilyTreeDNA says I'm 45% Scandinavian, AncestryDNA says 3%, and 23andMe says 1.9%.   [Compared to perhaps 1-2% from genealogy research.]

*  If you consider France and Germany to be representative of Western and Central Europe, then the AncestryDNA says 66%, FamilyTreeDNA says 32% and 23andMe says 24.7%.   [Compared to perhaps 28 to 32% from genealogy research.]

*  Only 23andMe provides non-specific ethnicity results, saying I am 23.5% "Broadly Northern European" (which could be Scandinavia, Western and Central Europe).  AncestryDNA and FamilyTreeDNA don't provide any "broad" results.

So do you see why I am still confused?  Also, AncestryDNA and FamilyTreeDNA have changed their ethnicity estimates in the past year or two.  

5)  My understanding for the disparity between these results rests on three factors:

*  The estimates are from DNA test results in reference populations in the specific areas.  Very few of these European populations are homogenous - we know that the British Isles have had significant immigration over the centuries from Scandinavia (Viking, Norman), Iberia, and western Europe (Angle, Saxon, etc.).  Perhaps that explains the British Isles and Ireland ethnicity disparities.

*  The autosomal DNA in our chromosomes comes from ancestors from thousands of years ago, not just 7 generations ago.  

*  Each testing company uses the same chip, but tests different numbers of SNPs, or gives more importance to certain SNPs.

Obviously, I am not an expert in this - just a confused customer and user.

If the tests all agreed, and were really different from my genealogical estimates, then I would think that I have a serious genealogy research problem.  But 23andMe seems to match my genealogical estimates pretty well, especially if I apportion the "broadly Western European" segment to the British Isles and France/Germany.

One concern is that each of the DNA testing companies seem to claim that the results provided are definitive for each person.  Obviously they are not, at least in my case.  We saw a lot of DNA test results on the Finding Your Roots TV series on PBS last year, and I anticipate we'll see more this year when the 2014 season starts in September.  I think they are using 23andMe for those tests, but I'm not positive.  

There was quite a bit of helpful discussion in the comments to my earlier post My Autosomal DNA Quandary  (posted 22 August 2013).  Since then, I have worked a bit in GEDMatch to try to find chromosome matches.  I have not investigated DNA Tribes to date.

Some questions:

*  How well do your test results match across companies?

*  What are the uncertainty bounds for each test company?

*  What am I missing?

*  Should I just accept that the reference populations and methodology are different between test companies?

*  Will the estimates from the testing companies be improved again and again over the coming years?

Reader comments will be appreciated!

The URL for this post is:  http://www.geneamusings.com/2014/08/my-autosomal-dna-quandary-persists.html

Copyright (c) 2014, Randall J. Seaver