A question containing the following paragraph appeared in WaPo’s “Ask Amy” column a few days ago (the discussion was about alarming and unwanted revelations that are sometimes fallout from online DNA tests):
After 50 years of genealogy research, I did a DNA test and found out that neither of my male grandparents were my biological grandfathers.
My assertion (agree or disagree): I do not believe it is possible to find out what the writer claims solely from an online DNA test.
I’ve done 23andme, and the report you get presents you with a list of people (strictly cousins of various degrees, in my case) you are likely related to IF they have consented to share their test results, and of course, if they have also done the spit-in-a-tube thing with 23andm3.
Now if a person you always assumed was your first cousin, for instance, took the same test from the same company, and it turns out you don’t share any DNA, your report won’t explicitly say that-- they simply will not show up in your list of potential relatives. So when you and Mary Lou get on the phone and each of you finds out neither of you showed up as first cousins in your 23andme reports, okay, you’ve found out that you don’t share DNA and you’re not cousins. The parents you’ve always assumed were siblings aren’t. I can see how a 23andme report would reveal that. And yeah, that would be interesting at best and devastating at worst.
But I can’t envision any way that an online DNA test report would show me that “neither of my male grandparents were my biological grandfathers.”
Even if several people in my parents’ generation took the spit-in-a-tube test and found out some or all of them weren’t related… how would this reveal anything about MY grandfather, let alone BOTH my grandfathers? But anyway that didn’t happen. The letter writer said "I took a DNA test."
I know doing online DNA testing can reveal family secrets regarding parentage, but this claim about the grandfathers doesn’t make sense.
I think people think that the online DNA testing is like what you see in cop shows, where some unknown DNA is found on a soda can and then compared with a vast national or international database and through the clever interpretation of mitochondrial DNA, family trees readily pop into view. The spit-in-a-tube results aren’t that dramatic or comprehensive. They compare your DNA with others who’ve also sent their spit in to the same company AND given permission both for the comparison and for the sharing of results.
NOTE: I’m not saying it’s impossible to use DNA to find out that both your grandfathers are not related to you, just that it’s not possible with basic online DNA spit-in-a-tube testing. Maybe the “other genealogy research” referred to was where the revelation came from. But I maintain it wasn’t from the online DNA test.
Am I all wet here or is Amy’s letter writer?