Monday, September 17, 2012

DNA: Matches in Common, part 1

One of my father's closer relations in the genetic pool at 23andMe also matches his paternal first cousin, once removed.  Here is what the graph looks like:

23andMe
J. H. compared to D. W. and Jody's Dad

J. H. matches D. W. on the same area of Chromosome 2 that he also shares with my father.  D. W. is in the generation older than my father and shares a slightly larger segment with J. H.  The relation is still distant, beyond third cousins.  The chances of inheriting the same intact segment is random, but here it is.

This match in common was surprising because it seems that J. H. shares an ancestral line on my father's mother's side as well.  If you travel back to Massachusetts in the 1630s, you will find the couple John Strong and Abigail Ford.  My preliminary research indicates that J. H. is descended through their son Jedediah while my paternal grandmother was descended from another son, Jerijah.  400 years later, it is not likely (dare we say improbable?) that such a large segment of DNA would still be intact from John Strong or Abigail Ford.

The new results demonstrate that there are more recent common ancestors, not in my father's mother's tree, but in my father's paternal grandmother's tree.  See how adding a cousin for comparison helps?  You still need to research records as we have been all these years to figure out where J. H.'s tree merges with mine.  It's like getting the answer first and figuring out the arithmetic later.