Tuesday, March 18, 2014

DNA : Ancestry Composition - Tweaking the Results

When I wrote about my Ancestry Composition results from 23andMe before, I didn’t realize that the numbers could be ‘tweaked’ just a bit, depending on how conservative or speculative an estimate you wanted to have.

For example, here are my “Conservative” estimates of my genetic make-up : 98.7% European, 1.3% Unassigned.

Note that a full 59.0% is Nonspecific Northern European.  That means that 23andMe found the markers in a wide enough group of places that they couldn’t say that part of my DNA came matched a specific population in, say France, for instance.  When you look at the “Standard” estimate results, you will see that play out.

Here are my “Standard” estimates of my genetic make-up : 99.8% European, .1% Sub-Saharan African, .1% Unassigned.

Notice in the “Standard” estimate, I pick up .1% of Sub-Saharan African.  If I’m reading the results correctly,  I have an ancestor back about 10 generations that was from Africa.  At 10 generations, there are 1024 ancestors to choose from.   Also, in this chart I have .3% Iberian and 1.1% Nonspecific Southern European.

Here are my “Speculative” estimates of my genetic make-up : 99.9% European, .1% Sub-Saharan African, less than .1% unassigned.

Now this is where I find it interesting.  Not only do they speculate that the .1% DNA that is Sub-Saharan African comes from Central & South Africa, but look at the break-out of the Southern European : 1.6% Italian, 1.3% Iberian and 1.3% Nonspecific European.  This is where some of the mystery comes in – I know of no ancestry in my paper trail genealogy that comes from these locales.  I’m speculating that this DNA comes from the ‘unknown’ ancestry of my maternal great-grandmother.  The breakout of 42.3% British & Irish and 14.4% French & German is more in line with what I would expect, based on the paper trail genealogy.

With both of my parents being tested, it will be interesting to see if my results change once they are tied to my account.  I also want to know if my theory about the maternal ancestry hold up.  I would be surprised, for example, if the southern European DNA shows up on my dad’s results.

Looks like the results get even better if you have a parent or child in the database :

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