Michael Cooley's Genetic Genealogy Blog GEN • GEN
18 Apr 2016

Update for Cooley DNA Group CF02

You've perhaps had time to read my email of last weekend. I intend now to send emails to individual groups with specific recommendations and have already sent one to CF07.

For now, I've split CF02 into four groups as follows (see DNA Results):

The testers in the main CF02 group have no proven descent from Benjamin Cooley of Springfield, MA and have had no advanced SNP testing. Many of them may well be Benjamin descendants but there is neither genealogical (correct me if I'm wrong) nor advanced genetic SNP testing that strongly indicates the probability.

Likewise, CF02/A has no known descent from Benjamin but has tested the SNP U152 and, like the Benjamin testers, is negative for it. Also, one of the testers is believed to have descended from Samuell Coley/Cooley (c1615-1684), who was a contemporary of Benjamin's and, therefore, not a descendant. It's possible he was closely related, however.

For the most part, CF02/B testers are known to have descended from Benjamin and, to a degree, have had advanced SNP testing. Benjamin's distinct Y-SNP fingerprint is buried in David Cooley's (#128108) Big Y results. We need a matching tester to tickle it out.

The CF02/C tester, a descendant of Hezekiah Cooley, born in 1802, has told me that he has never had a good reason to suspect a Benjamin descent. That he is positive for U152 proves the point.

So, other than the sharp genetic distinction between CF02/B and CF02/C and the likelihood that there are additional Samuell descendants among CF02, everything is pretty fluid. Advanced SNP tests can help sort it out. But before we can make any real progress, another known Benjamin descendant needs to take the Big Y test. Here's why.

David's most recent matching SNP, Y15926, may be 2500 years old. That doesn't tell us a great deal. In fact, CF09 has the same SNP. Judging from CF09's STRs, however, there is not a close relationship between the two group. Y15926 is just not helpful.

Dating SNPs is not a science. That Y15926 may be 2500 years old is a gross estimate. We know its relative position on the SNP tree, which helps. And there are estimates about the average mutation rates for SNPs, but the calculations are unreliable. Some put that estimate at about 1 mutation in about every 150 years, others in about every 180 years. But if we multiply David's 23 novel SNPs (those for which he has no matches and are, therefore, much younger than those that do have matches) by 150, we end up with 3450 years—far greater than the currently estimated age for Y15926. In my case, I have only five novel SNPs, that is, SNPs that entered my lineage between the time my Edward Cooley (a son of John Cooley of North Carolina) was born in 1763 and my own birth in 1950. That's an average mutation rate of only 37 years! A descendant of John's son James, born in 1772, has only two novel SNPs, an average of 90 years per each mutation. But any way we cut it, David's currently known terminal SNP is ancient.

However, if another Benjamin descendant tested, we would know all SNPs down to Ben's own birth in the early 17th century. I don't know that year, but David was born more than 400 years later! Out of his current 23 novel SNPs, how many novel SNPs would that leave? Maybe five? Maybe ten? In any case, a second test from the right person will increase the known SNP tree by perhaps 15. This will make the new tester a DNA pioneer by providing the genetic genealogy community with a handful of previously unknown mutations—and we will have a usable DNA fingerprint for Benjamin. One cautionary note, however: if Samuell was closely related to Benjamin, there may not have been sufficient time for a SNP to emerge that was unique between them—but perhaps so.

In a previous post I recommended that R1b testers, including CF02, do the M343 SNP Pack. Although there would certainly be a strong distinction between Hezekiah Cooley descendants and Benjamin Cooley descendants (the U152 SNP) anything else would be iffy at this point. But once the SNP tree has been sufficiently developed, we stand to be able to make such distinctions based on even a single SNP test for $39.

Although the basic concept of Y chromosomal descent is straight-forward, multiple iteration of a single idea can make the data very complex. Future posts should better illuminate the ins and outs of SNP discovery.