Thursday, July 21, 2016

Rare Tidball DNA

There is more Tidball family history waiting in the wings, but the blogger is pretty much immersed in DNA this week at the Genealogical Research Institute of Pittsburgh (yes, GRIP). This, of course, means the blogger is in Pittsburgh, and doesn't have access to all his paper Tidball files. So, this week's blog just presents some musings about how DNA might help in Tidball research.

For you non-genealogists, you don't need to know much about DNA or genetic genealogy to read on. The most important thing is this: if you have ancestors, you have DNA. Of course, it goes the other way, too... if you have DNA, you have ancestors! Genealogists base their research conclusions on information from two general kinds of sources: records and authored works. Records include things like death certificates, censuses, and citizenship papers -- generally speaking, documents that "record" (and preserve) information about family history events. Authored works are just that -- compilations of evidence, ideas and conclusions from another researcher.

For something you can't see, DNA is pretty hot stuff in genealogy. It seems like an entirely new kind of source, but I think of it as just another kind of record -- carried forward in a different medium. It is a record of the genetic make-up of the great-grandparents, grandparents and parents who passed it forward.  DNA mutates -- if it didn't, we would all have matching DNA and probably pretty much all look alike. Because DNA mutates, lines of genealogical descent can be differentiated. People with closely matching DNA probably have a fairly recent common ancestor. If they had a more distant common ancestor, mutations would likely have created more genetic distance between them.

Y-DNA is useful for relating men with shared surnames, because every male received his Y-DNA from his father, who in turn received it from his father, and so on. Until a mutation occurs, males in two male straight lines of descent will have matching Y-DNA. So, even where men of the same (or variant) surname differ only only a few "markers," they are likely to have a common ancestor within a dozen or so generations.

I have tracked the Minnesota Tidball ancestry back to a Thomas Tidboald, born about 1739, who lived at North Molton in Devonshire. I suspect that he was a son of a Tidboald family that in the 1730s lived in Exford, is less than 10 miles from North Molton. Y-DNA might either disprove or lend credence to my hypothesis. Traditional research tracks a group of Tidballs who settled in Ontario in the last half of the 1800s back to the Exford Tidboalds. If my hypothesis is correct, living male straight line descendants of those families should closely match living males in the Minnesota Tidball family.

I have tested the Y-DNA one of my Tidball brothers-in-law. As we learned a few posts ago, the Tidball name is rare, and it appears that possibly no other related living Tidballs have tested because the FamilyTreeDNA Y-DNA database thus far reports only two men who come even close to matching my brother-in-law at 37 markers. Neither of those men is a Tidball.

DNA is not an easy fix to genealogical research problems. I might learn more if I can locate and test a living male straight-line descendant of the Ontario Tidball family. It would take a good deal of genealogic detective work to identify a candidate for testing. But, if I could find and test a candidate, it might give me more confidence in the hypothesis that Thomas Tidboald of North Molton came from Exford.

Of course, autosomal DNA tests might also help, but that is another story for another time.

No comments:

Post a Comment