Tuesday, February 26, 2013

DNA tests - Making sense of percentages

My parents and I have all done DNA testing, at both FamilyTreeDNA and 23andme.

The image below shows my mom's "Ancestry Composition" from 23andme.  Ok, so obviously, mostly European. Got that. But what exactly do these percentages represent? I was trying to make this more clear in my mind as to what the 0.1% signified.

So I started thinking. Mom has a number of percentages that are at 0.1%. In order to make that equal 1 person, I would have to have 1000 ancestors represented in this evaluation.  Then I went looking for how many generations it takes (remember, your number of ancestors in each generation doubles) to get to 1000 ancestors.  The answer? 9.  (I used this website.)

By the time you get to the 9th generation back from you (that is your 7th great-grandparents), you have 1023 unique ancestors. However, it is unlikely that there are no intermarriages and duplicated individuals.  So generally, the 9th generation back gets us 1000 ancestors. That website gives a general birth year of 1680 for this generation. (A previous post at this blog counted the ancestors that I have identified by generation; I have 83 of the 512 in this generation identified.)

So taking mom's percentages, based on 23andme's speculative percentages, out of 1000 ancestors I get the following numbers of people in her ancestry:

466 British and Irish
117 French and German
45 Scandinavian
312 Northern European
42 Iberian
9 Southern European
1 Ashkenazi
5 European
1 Sub-Saharan African
1 East Asian/Native American
1 Unknown

Cool, right? That is a little more...understandable. Concrete. Essentially mom is half Irish/Scottish/English/Welsh. Most of her known ancestors in this group are Irish/Scottish. And she definitely has duplicate ancestors - her paternal grandparents were first cousins (surnames McFEATERS and McCACHREN).

Dad's results:
305 British and Irish
127 French and German
124 Scandinavian
360 Northern European
9 Sardinian
5 Italian
25 Southern European
33 Eastern European
9 European
1 South Asian
1 East Asian/Native American

My results:
409 British and Irish
84 French and German
17 Scandinavian
418 Northern European
11 Iberian
4 Italian
32 Southern European
5 Eastern European
16 European
2 South Asian
1 Unknown

I've got some of these results that I am scratching my head about, but being able to take Dad's results, Mom's results, and my results and compare them, I can see patterns.  Got the Italian from Dad (not surprising, with his Gredler family being in Tirol in Austria, near the Italian border), Iberian from Mom (NO CLUE about this group), and missed some of the markers. I didn't get either one of their East Asian/Native American marker, and I didn't get Mom's Ashkenazi or her sub-Saharan African marker.

Another excitement is that one of the matches at 23andme is someone that I talked genealogy with probably 10 years ago. We know we are cousins and have researched together previously on the McFEATERS and CAMPBELL families in Pennsylvania. So now I have my first paper AND genetic cousin match!!! So exciting!
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