Related Twice: mtDNA and Chromosomal Mismatch

I received a 23andMe message a few days ago notifying me that my maternal haplogroup was a match for another member. Considering I have a handful of matrilineally-linked cousins already on 23andMe, it seemed like a no-brainer. This is one of my Italian relatives reaching out. Ha, WRONG!

I presupposed that this person was of Italian ancestry based on the fact that my mtDNA is along an Italian line of woman and that every other person whom has contacted me also shares segments of chromosomal DNA. Of course, all members of the same maternal haplogroup have a common female ancestor thousands of years in the past. However, I’ve never had a mtDNA match contact me that wasn’t related to me through that line. She suspected I would be a tremendous help for a mysterious part of her tree along the mtDNA line. It turns out, I will be no help, at least for this part of her tree.

It turns out that our chromosomal match is from her father’s line, not her mother, meaning I am not closely related to her via the mtDNA line. I was flabbergasted after viewing photos of potential relatives. I guess the eyes sometimes see what they want to see. DNA, however, doesn’t lie. We are probably fifth cousins or so in the near relation and also the same maternal haplotype of ancient relation.

The good news (or bad news depending on how tedious the research gets) is that neither of us can pinpoint the common ancestor in question. Based on the admixture results of our common segment, it will be a British ancestor, which is the only possibility from a genealogical perspective as well. I hope we can pinpoint the correct ancestors so I can write a followup to this bit of genealogical irony.


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