Michael Cooley's Genetic Genealogy Blog GEN • GEN
25 June 2016

New Big Y Results for Cooley Group CF02

Note that the graphic, not the text, was updated with new findings on 15 August 2016.

A second descendant of Benjamin Cooley of Springfield, Massachusetts has tested for the Big Y, a survey of about ten million positions on the Y chromosome. The advantage in having these two men test is that they're descended from Benjamin through different sons—two distinct lines. Kit #128108 (David Cooley, former President of the Cooley Family Association of America) is descended from Benjamin's son Daniel Cooley, and kit #319005 (Doug Cooley, Genealogist of the CFAA) is descended from Daniel's younger brother Joseph Cooley. In other words, Benjamin Cooley is their Most Recent Common Ancestor (MRCA), and that means their shared mutations come to them via Benjamin down their respective lineages. And that means that Benjamin had those mutations at birth, and so we now have a distinct genetic fingerprint for him.

SNP Y15926 emerged with the birth of a man about 2800 years ago (current estimate). The emergence of the first block of SNPs (green) may have had a terminus date of about 900 years later, say ca. 100 C.E., and the next 17 SNPs emerged between that date and the birth of Benjamin Cooley, ca. 1615.
SNPs are people too

Well, that's overstating it a bit, but recall that there are essentially only two kinds of mutations (called Single Nucleotide Polymorphisms or SNPs)—those that are named and those that are not. Typically, SNPs aren't named until two testers are found to match. Firstly, the match provides verification that we have something useful. Secondly, the newly discovered SNPs can be worked into a tree, as shown here, which is evermore expanding. And remember that new Y-SNPs occur along with the births of men. Therefore, each SNP named in the diagram would have a name attached—if we only knew who they were!

The above graphic is simply my cursory rendering of this new branch of the world-wide Y-SNP tree. The matching SNPs between Doug and David are now under review at FTDNA and elsewhere. Some of the SNPs may be dropped as being unreliable and additional SNPs may emerge through further analysis. What's left standing will be named. (To read about naming SNPS, see the "sidebar" in Y-SNP Discovery, Part I.) Several styles are used to refer to unnamed SNPs, but they boil down to having three parts: the value (A, C, T, or G) found in the population at large, known as the "ancestral" value, the tester's newly discovered mutated value, known as the "derived" value, and the position on the chromosome at which the SNP is found. I use a convention that provides the information in the form of ancestral+position+derived, for example, C7791641G where G is the mutation.

Putting SNPs into a timeline

When David tested a year and a half ago, the discovered SNPs (in all the green boxes listed above kit #128108), belonged only to him. We now see that six of them also belong to a tester named Brown. By virtue of the fact that Brown shares a minority of the SNPs and that they are presently shared with three people instead of only two, they are deemed to have emerged much farther up the tree and are, therefore, older. (See Y-SNP Discovery, Part II about how SNP blocks break up into smaller blocks and, conceivably, eventually into blocks having only one SNP each.) In this way, the large block in the center, now having seventeen SNPs, will eventually break up (I have some ideas about who should test to accomplish that). With each break, an ordering occurs and the timeline slowly reveals itself. The blocks are arranged so that those having the fewest matches are placed below those that have the greatest number of matches. As we climb the tree, we eventually get to a block of SNPs that are found in every living male on the planet. Those are the oldest SNPs and belong to the dawn of humankind.

Aging SNPs

The two SNPs left to David (#128108) emerged at points in the lineage between Daniel's birth and David's own birth—a period of about three and a half centuries, or an average of about 175 years between mutations). In roughly the same period, five mutations occurred in Doug's line. This lopsided rate of mutation is common and is also found among our Big Y testers in CF01 and CF07.

This tells us that mutations occur randomly through the generations. But the number of known mutations (SNPs) found on the Y chromosome is now in the tens of thousands, a number that's increasing daily. By averaging the number of SNP occurrences over many lineages, an average mutation rate is discovered. As the test samples increase, that number becomes more realistic and can be used to give a rough approximation of the age of any particular SNP or SNP block. Using these calculations, Y15629 is presently guessed to be about 2800 years old.

Determining Relationships

Note that the CF09 Cooley lineage broke off at about that time. This was, of course, long before the age of surnames. That the two lines now possess the name Cooley is merely coincidental, although it's possible that an individual from one side adopted the name Cooley from the other. That, of course, can happen for any number of reasons. In other words, it could be that there was a historic, not a genetic, connection between the two families anytime during the genealogical timeframe.

And then we see that the Brown tester's line broke off the Y15926 trunk six SNPs, perhaps 900 years, later. In other words, the Browns are closer related to the CF02 Cooleys than are the CF09 Cooleys.

Now what?

That's always and will always remain the question. First, over the next few weeks my diagram will be cleaned up with official SNP names along with some jostling of the SNPs themselves. In time, the picture will expand as new testers come online. Our principle objective is to ID SNPs that are as specific to Benjamin as possible. But because of the relatively slow rate of SNP mutation, his SNPs might have been identical to those of his brothers, first cousins, or even third cousins. Yet in order to learn even that much, the large 17-SNP block needs to be parsed out. I know an individual in England who is doubtlessly of a collateral line to Benjamin. A Big Y test from him might make an effective first attack on that block.

Once we're left with a small set of SNPs that look particularly "Ben-ish," others in CF02 can inexpensively test for them. Those persons not having them, just as the Hezekiah Cooley descendant has a mismatch much farther up the tree, would be shown not to be descended from Benjamin but are, instead, of a collateral branch. Those who have the Ben-ish SNPs will know to continue to pursue the genealogy of the clan.


David's and Doug's tests are a huge step in the right direction. Their distinctive places in the Y-tree of man are now permanently recorded, and we're well on the road toward having a specific genetic identity for Benjamin, which will serve as an important marker through which we will, eventually, discover his own heritage and learn more about just who belongs under his name on what is probably, thanks to Mortimer Cooley, the largest of all known Cooley genealogical trees.1

1 Mortimer Elwyn Cooley (1885-1944) founded the Cooley Family Association of America in 1936 and published The Cooley Genealogy in 1941.