Sunday, May 29, 2011

Autosomal DNA Matching and the Importance of Testing Multiple Family Members

I was contacted by a new cousin at 23andMe. She noticed a matching surname on our lists and requested to share genomes. Upon doing so, we discovered that we do indeed have a match. She matches me on 6.5 cMs of Chromosome 14 and Relative Finder predicts that we are seventh cousins. We quickly determined from our family trees that we are 9th cousins once removed, which slides in right at the end of the predicted range of 4th - 10th cousins. Our common ancestral couple is John Spofford (b.1678) and Dorcas Hopkinson (b.1676) from Massachusetts. Done. Great! Right?

Not so fast. Upon further investigation, I noticed something very interesting. The common ancestral couple is on my father's side, but my mother shares this match with me!  This "Spofford" Cousin matches not only me- but my mother, my sister and my two nieces on Chromosome 14. Therefore, the match on Chromosome 14 must come from my mother's ancestry, not my father's. So, is this once promising match a total failure? Take a look at Chromosome 5. That little dark blue smudge is a match that my sister shares with this cousin, but my mother and myself do not. Now, that one could be from my dad's side!

For a closer look, please click on the charts to enlarge

Actually, this Spofford Cousin matches both of my sisters on Chromosome 5. Dark blue and light blue smudges show up on Chromosome 5 on the chart below, signifying that my sisters share this 6 cM match.

Since I do not have my father's data at 23andMe, but I have tested his two siblings there, I checked to see if either one matches this cousin. Neither one does. This makes it impossible at this time to absolutely determine if this stretch of matching DNA on Chromosome 5 was inherited from the Spoffords. If, in the future, other matches show up that are descended from the Spofford or Hopkinson Families that will clarify the situation. Since I do have my father's data over at FTDNA's Family Finder, another possibility is to compare his raw data file with his Spofford Cousin at an independent project that compares data files from both companies, like GEDmatch (if she is willing to submit).

Because of the matching DNA on Chromosome 14, I examined my Spofford Cousin's family tree a bit more to see if I could determine from where that match might originate. I couldn't help but notice the surname Shellenbarger figuring prominently on her tree. I have written in the past about my mother's mysterious Stolebarger great great grandparents here and here and my theory that their often misspelled surname with its many variants could have evolved from a similar name. Sure enough, both the Shellenbargers and the Stolebargers were German immigrants living in Pennsylvania in the early 1800s and members of both families ended up in Iowa by the late 1800s. I could not find a solid connection, but this match will cause me to be more keenly aware of my mother's links to these Pennsylvania Dutch families, including our Roderick, Long and Roemig ancestors. This may even lead me to finally start that Stolebarger Y-DNA Project. In fact, I still have an unused kit sitting here waiting for a Stolebarger, Stolabarger or Stoalabarger male. Any takers?


  1. My Ggrandmother a daughter of Abigail Garrett went by the name of Hannah Clifton so until recently we--the descendents of Hannah Clifton--assumed than Hannah was the daughter of John Thomas Clifton. Recently uncovered records now indicate that Hannah was perhaps the daughter of John Larter. So at this point I do not know whether I descend from John Larter or John Thomas Clifton. One of my female 3rd cousins is definitely known to descend from John Larter & Abigail Garrett and another female 3rd cousin is definitely known to be a descendent of John Thomas Clifton & Abigail Garrett. I am thinking that if both of these 3rd cousins of mine were to test with 23andMe then the one showing the closest relationship to me would descend from my GGgrandfather (either John Larter or John Thomas Clifton) and thereby I would have the answer to which of these two men I descend from. Does this approach make any sense or does it need to modified or refined?

  2. I see that I need to add the following information:

    My GGgrandmother Abigail Garrett married first John Larter and second John Thomas Clifton.

  3. William - That makes perfect sense. Just keep in mind that the further out you get from the common ancestor, the less reliable autosomal DNA testing. There is a ~10% chance that a 3rd cousin will not be detected at all by Relative Finder (23andMe) or Family Finder (FTDNA). Third cousins should share ~.781% of DNA, so your half-third cousin should theoretically only share ~.39%. Those numbers are only averages and do fluctuate quite a bit, so it may not be as clear-cut as we would like. My concern is that at this level, you or they may only inherit DNA from one of the ancestral couple anyway, not both. You may get lucky with the first round of testing and get a clear answer, but you may have to test someone who is ONLY related to John Clifton or John Larter and don't share Abigail Garrett. Did either of them have children by another wife. You might have to go one step higher on the tree and test descendants from their brothers.
    Thanks for commenting and please let me know what happens.

  4. This is great! I have EXACTLY the same situation that I found on Saturday! I sent a sharing invite to a cousin on 23andme and she accepted. I compared her to me, my mother and my uncle on Family Inheritance Advanced and was confused at the results. I matched her on two chromosomes, 1 and 12 but my mom and uncle both matched her on chromosome 4 (????) When I compared her to my father, he matched her on the exact same to places that I did! WHOA! The interesting thing is that, prior to my mom and dad meeting in Memphis, there is no other KNOWN connection between the two families. My mom's family is from middle TN and my dad's is from AL and FL.

    Our new cousin is from the same town in AL that my paternal grandfather's family is from so I'm pretty sure that is the connection through my dad, but I have no idea about the one through my mom. Our cousin is just getting started with genealogy so we've got a bit of work to do to get it figured out. But I'm excited!