I read a very interesting summary about the reliability of DNA with respect to confirming familial relationships in the latest issue of Quarterly, the journal of the Association of Professional Genealogists (December 2015, volume XXX, number 4) by Dr. Blaine R. Bettinger (Understanding DNA Sharing Probabilities among Close Relatives). In the paper, he discussed how difficult it can be to determine whether people are related past the level of 4th cousins. And, by the way, he did it language that all of us can clearly understand, something that is not always the case with articles on such technical subjects.
Now, of course, many researchers have had success in finding members of their family who are very distant cousins, mostly through traditional genealogical means I think, though. I am not convinced yet that people can very often find those same individuals just through DNA. Dr. Bettinger points out that, because of the way DNA is passed down through generations, with 5th cousins and beyond “[t]here is a greater chance of not sharing DNA than there is of sharing DNA. Accordingly, lack of sharing between fifth cousins or a more distant relationship is not meaningful evidence.”
That is kind of what I was getting at in my post of 26 January 2016 (Why would we care about 4th cousins? Or even more distant relatives?). As I said, DNA can be great. I met a few 2nd cousins through 23andMe, but only because we all had our DNA tested by that company! That is the biggest problem I see in finding those elusive family lines when other genealogical information is missing. If no one in those branches gets tested we might never come across them let alone confirm their relationships.
Having said that, of course, my wife and I both had our DNA tested and I persuaded a male cousin to do so as well. It was done just in the hope that there might be other family members out there who might test theirs and we might make contact with each other. I guess that’s the real game of family research, anyway – get more lines in the water (cousin bait as Randy Seaver says).
I am looking forward to Dr. Bettinger’s next installment about DNA in Quarterly but I also hope he will publish these comments in other journals where non-professional family historians will be able to read them.
I do see DNA testing as a tool but not the end-all-and-be-all. Genealogists seek blood relatives for the most part although not all members of real families are always genetically related (as I stated in my post of 13 January 2015 (Don’t Forget About Those Half-Brothers and Sisters).
If you can find cousins and confirm their relationships with DNA, that’s great! But I think there is still no substitute for vigorous traditional genealogical research in assembling a true and accurate family tree.
Wayne Shepheard is a volunteer with the Online Parish Clerk program in England, handling four parishes in Devon, England. He has published a number of articles about various aspects of genealogy and is the Editor of Relatively Speaking, the quarterly journal of the Alberta Genealogical Society. Wayne also provides genealogical consulting services through his business, Family History Facilitated.