When should we trust DNA testing

+5 votes
I certainly need to learn more about DNA testing.   While I had a genetics class at KU in 1974,  things have certainly changed!

Last year I had planned to delve into the topic but my enthusiasm was squashed by a CBS news report about the popular trend of genetic testing for genealogy.

The investigative news report went:   CBS news  (OK, maybe NBC or ABC)  took three identical twins in their twenties  (yes,  I verified it's possible to have three identical twins).  First,  they did the  "court room level" DNA testing to show the girls were all identical.  They then performed genealogy level DNA testing on them, using labs that are popular for genealogy testing.  I THINK they used different labs, but the girls didn't use their own names.   The results for the three "genealogy level"  tests were NOT particularly similar.

Am I being too suspicious???   Ok, you don't have to look at my profile,  I'm a retired engineer and engineers certainly have  "a reputation".

Would love to hear your thoughts!

in The Tree House by Peggy McReynolds G2G6 Pilot (448k points)
It was CBS news.....
Using identical twins seems a little overdramatic, when they could make the same comparison just by sending one person's DNA to different labs.

It would be more interesting to compare results for fraternal twins, or any other full siblings.  And not just at different labs, but at the same lab.

In that case, you'd have identical ancestry, but non-identical DNA, and you'd find out how much the reported results are affected by random noise.
Hang on ... how can identical twins have different DNA? What relationship did it show between them?
They were proven to be identical twins....... the lab testing was what was flawed.    If you want the best detail  google:   Inside Edition identical triplet DNA testing
Thanks for all the comments..... It has given me the incentive to proceed with DNA testing soon.
Great observation RJ......  and to imagine the press overdramatizing!

Now, now Peg, a retired engineer relying on an Inside Edition report on genetic genealogy? Tsk,tsk. Remember, we do have a reputation to uphold!

Glad to see that you've begun the process of redemption by asking here on G2G. As additional penance you are assigned to read Blaine Bettinger and Roberta Estes' blogs and all of Edison's G2G posts. If you really want to go all out I highly recommend the MIT biology classes on EdX, 7.00x and then the 7.28x series, not specific to genetic genealogy but an excellent introduction to the science of molecular biology in general and a great background for understanding the science underlying genetic genealogy. And always remember to save a large dose of skepticism for the journalists.

And in case my judgement seems to harsh, I leave you with my favorite engineering adage:

Question: Why should you never argue with an engineer?

Answer: Because it's like mud wrestling with a pig. You can never win and sooner or later you realize that they're enjoying it.

Interestingly, I find engineer's spouses generally enjoy that one more than the engineers do.

And one of my favorite quotes, I think you may enjoy:

The power of accurate observation is commonly called cynicism by those who have not got it.
George Bernard Shaw


Thanks for getting me back on  the path.    Since I've also been married to an engineer for 40 years,  you'd think it wouldn't be necessary!

I'll be reading Blaine, Roberta and Edison's blogs soon.


5 Answers

+23 votes
Best answer

Peggy, have faith!  

That Inside Edition "report" didn't look at the autosomal DNA matching at all; they ignored the genealogical aspects of the testing which, I guarantee, would have been consistent with the twins' biological relationship. And, arrrgh!, like umpteen YouTube videos, all that was considered was "ethnicity." Which, apart from being a very unfortunate and inaccurate term, is at this stage of the technology and vetted database depth--unlike matching for genealogy (but do be aware that's useful with autosomal testing only out to about 4th cousins)--as much smoke-and-mirrors as it is science.

You can read some of my recent thoughts here. It's an advertising ploy that has worked remarkably well in Heinz 57 America; not so well at all elsewhere. But because it has worked so well and has sold so many millions of autosomal DNA tests, we're stuck with the distasteful hype for the time being. Trust me, professional anthropology and population geneticists throw things at their televisions every time a "traded my lederhosen for a kilt" commercial comes on.

by Edison Williams G2G6 Pilot (351k points)
selected by Douglas Beezley
Aarrggh! That stupid TV ad drives me nuts. Most of the people I match with on Ancestry ONLY took the test for the ethnicity part. They have zero interest in the genealogy. Their sample base for ethnicity was very limited.  Each company has its own sample base for ethnicity and that makes it not possible to get the same results across companies.
I agree. They only do the test for ethnicity purposes.

I have several matches at 2nd to 4th cousin level and they dont have any family trees or surnames list so I cannot even begin to guess which side of the family they come from!!

As for Ethnicity estimates - if you look at my maps on my profile, you can see that one estimate said I was East European and the other said I was more Scandinavian. I tend to agree with the Scandinavian estimate since I do have ancestry from Orkney in Scotland and they were KNOWN to be under Viking control 1000 years ago!!!

 I totally agree with your opinion about those stupid ancestry.com ads.

But that which causes me to scratch my head is this, in my opinion, irrational concern about ethnicity, while having no interest at all in genealogy.



While I share these sentiments and it is annoying when those who take the test for ethnicity don't bother to add any tree or respond to messages and have no interest in genealogy, at the same time I am glad they tested. While most people are not properly equipped to interpret the admixture reports, maybe they will learn something and maybe they will stay around for family history.

In any event more matches and more tests is good. There's at least the opportunity to contact and find more about their family. It's invaluable to adoptees. It improves family DNA circles, shared matches, and has potential to improve matches with phasing, etc. etc.

So, I temper my feelings about this, same as with folks whose interest in genealogy is sparked by finding celebrity or royal connections (surprise! we all have them!).

In my experience AncestryDNA customers who are testing solely for ethnicity are much more responsive than 23andme customers who are testing only for health. So there's that.

Very good points Nathan.
+7 votes
While there can be problems, the tests I’ve taken have correctly identified that my sister was a sibling and 2 first cousins were likely first cousins. My Y DNA test found a third cousin that paper genealogy confirmed. At least for close relative it works fairly well. The ethnicity tests are all over the map (literally). There’s a lot if statistics and probability involved and genetics doesn’t really follow the simple Mendelian model we learned in jr high.
by Doug McCallum G2G6 Pilot (449k points)
+5 votes
Just use it too lead you too connections you can verify,Thats my

advice.And then again,who am i too say..!!!!
by Wayne Morgan G2G6 Pilot (921k points)
+7 votes
DNA testing is very valuable when looking at DNA matches and seeing how they connect to your family, verifying relationships and giving clues to identify family connections where the paper trail is missing (due to missing or destroyed records). It is also extremely useful for identifying biological family of individuals whose biological family is unknown..eg. my step-grandmother was born illegitimately in 1920. He mother's side is completely Welsh, so I am using DNA matches to find her biological father (who appears to be completely English). I have used matches to identify the father of a child born in the early 1900s, and have identified the grand-father of an illegitimate child born in 1837 (just need to determine which of his 3 sons was the father).

I ignore Ethnicity estimates - they are just that.
by Michelle Wilkes G2G6 Pilot (143k points)
+2 votes

Hi Peggy, If you do an autosomal/Family Finder DNA test, you will get cousin matches in any of these surnames, including the question marks:  https://www.wikitree.com/treewidget/McReynolds-216/10

If you have a living male McReynolds relative (brother, uncle, McReynolds cousin) that will do a yDNA37 marker test, it will give you cousin matches on your McReynolds paternal line of forefathers.

With a yDNA37 marker test from FamilyTreeDNA, you can join the McReynolds DNA project https://www.familytreedna.com/groups/mc-reynolds/about, or the Scottish yDNA project:  https://www.familytreedna.com/groups/scottishdna/about

Both the Family Finder and the yDNA37 marker tests sometimes go on sale at Father's Day from FamilyTreeDNA.com. 

by Kitty Smith G2G6 Pilot (586k points)
Thanks for the help.   It's time to recruit my brother for the yDNA37

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