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Old 10-18-2017, 08:00 AM
 
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Interesting article in the Philly papers today, which many, I assume, already knew about DNA results:

These siblings took DNA tests and got different results. Why determining ancestry is rarely accurate

Our Italy/Greek numbers were about the same. But her results showed 37 percent British Isles, whereas I was 53 percent. She also showed 10 percent Scandinavian and 7 percent East Europe — neither of which even appeared in my results. And we’re about as Scandinavian-looking as Jennifer Lopez.

“It’s very difficult to accurately find your ancestry under any circumstances,” said Jonathan Marks, an anthropology professor at the University of North Carolina at Charlotte. “There has been genetic mixing for thousands of years. These tests are fun but rarely accurate — 10 percent Scandinavian could be no Scandinavian because the test could very easily be 10 or 15 percent off.”

“The methodology they use in determining the DNA markers is solid,” said Deborah Bolnick, an anthropology professor at the University of Texas. “The challenges come with interpreting those DNA sequences to say something accurate about your ancestry.”
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Old 10-18-2017, 08:19 AM
 
Location: Colorado (PA at heart)
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The tests are normally clear about the fact that the ethnicity report is only an estimate. However, even if it were 100% accurate, full siblings would still not get the exact same results unless they were identical twins. They do not share all the same DNA and although we do inherit 50% from each parent, contrary to popular belief, we do not inherit exact 25% from each grandparent or 12.5% from each great grandparent, etc. So comparing the results of full siblings isn't really a good example of why the ethnicity test is only an estimate. The articles about the identical triplets who got slight variations in their results is a better example.
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Old 10-18-2017, 09:28 AM
 
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Part of the problem is that some people see the DNA test as a 'silver bullet' which will 'tell all' rather than part of a process which includes some hard research. They have been encouraged in this by the popular view of DNA is being incontrovertible 'evidence' which is always right. I always thought of the DNA test as 'directional' rather than 'absolute'.

In my own case, the DNA test came after the research rather than before so its role was to corroborate what I already knew and to see if it threw up any surprises. It didn't!

The other benefit of the DNA test was in the matches. That has thrown up a few interesting contacts and has allowed me to identify a branch of the family that emigrated to the USA in the late 19th century from Lancashire. That was something I was unaware of.
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Old 10-18-2017, 04:03 PM
 
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At least it didn't tell them they were not siblings!

my sister and I got different results also. I was not surprised. The biggest difference was that I got 39% Ireland and she got 22% Ireland, and other areas differed as well. Basically the same areas in the world, just different percentages.
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Old 10-18-2017, 06:10 PM
 
12,906 posts, read 11,153,868 times
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Quote:
Originally Posted by PA2UK View Post
The tests are normally clear about the fact that the ethnicity report is only an estimate. However, even if it were 100% accurate, full siblings would still not get the exact same results unless they were identical twins. They do not share all the same DNA and although we do inherit 50% from each parent, contrary to popular belief, we do not inherit exact 25% from each grandparent or 12.5% from each great grandparent, etc. So comparing the results of full siblings isn't really a good example of why the ethnicity test is only an estimate. The articles about the identical triplets who got slight variations in their results is a better example.
According to my 23andme report, I inherited 27% of my DNA from my grandma. I was a little surprised, thinking it was exactly 25% from all four.
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Old 10-19-2017, 10:04 AM
 
Location: Colorado (PA at heart)
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Quote:
Originally Posted by JerseyGirl415 View Post
According to my 23andme report, I inherited 27% of my DNA from my grandma. I was a little surprised, thinking it was exactly 25% from all four.
Yes, I only got 19% from my paternal grandfather, which means I got 31% from my paternal grandmother. That's actually very consistent with the fact that I typically get about 29-33% in Southern Europe from most companies, because my paternal grandmother was Italian. The divide between Northern Europe and Southern can be much easier to distinguish so there is some level of accuracy to the ethnicity report, if you use broad regions. The more you try to narrow it down, the more speculative it becomes.
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Old 10-19-2017, 06:44 PM
 
Location: Ozark Mountains
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We are NOT identical. Not even twins are identical. The only persons identical to each other are CLONES.
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Old 10-19-2017, 08:06 PM
 
Location: Cumberland
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My dad and his brothers all took the test. Two of the brothers were nearly identical, one is 'off' about 10-15% on the listed ethnicity (less British, a bit more of everything else.) My ethnicity pie chart was nearly identical to my father's.

Ancestry still IDed all 3 as brothers, and me as my father's son. It also pegged known cousins from my mother's side. I was impressed. I do think the test overestimated my British % at the expense of German (Western European by Ancestry's language.) But, when you consider many of my German ancestors were from northern Germany, there might not be that much difference between them and the Angle-Saxon genes of Britain.
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Old 10-19-2017, 08:24 PM
Status: "Disoriented" (set 18 days ago)
 
Location: Coastal New Jersey
61,061 posts, read 58,301,649 times
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Quote:
Originally Posted by fvncresident04 View Post
At least it didn't tell them they were not siblings!

my sister and I got different results also. I was not surprised. The biggest difference was that I got 39% Ireland and she got 22% Ireland, and other areas differed as well. Basically the same areas in the world, just different percentages.
I'm one of 7 children, 6 living. Four of us had our DNA done. We are all different from each other. Not radically so, but, for example, my sisters show up with small percentages of Iberian Peninsula that I don't have.
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Old 10-20-2017, 02:28 PM
 
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DNA geneology testing is far from an exact science and they have certain error rates.
If you are comparing tests between 2 different DNA testing companies: forget it - they all have there different standards of comparison. If you are comparing intercontinental test (i.e. Western Europe vs. Northern Europe...or specifics like Iberian Peninsula heritage? haha...yeah I am sure they will tell you that but the technology just isn't that sophisticated): forget it - DNA testing just won't do a good job as the error rates will just be to huge.

They do fairly well telling if you are from Asia vs. Europe vs. Africa for instance, but beyond that....
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