Michael Cooley, BA, MA – 16 August 2022
This email is going out to both Bennett groups I'm working with, as well as other interested researchers. First, for the benefit of those who might not have heard from me in a while, here's a recap.
I largely want to discuss the hybrid tree for the Blackwater Bennetts. It's far from complete but we've had some pretty good movement. Primarily, however, it will serve as an illustration as to genetic genealogy's objectives, about how and why this works, and as a springboard for clarification about what it can't and should not do.
Hopefully, everyone understands by now that the Y chromosome is what makes a man a man, that it passes straight down the male lineage without any genetic input from the mother's side, and that a mutation is occasionally introduced that defines a new genetic branch and slightly alters the Y-DNA stream from that point on.
These mutations are crucial to understanding Y chromosomal inheritance for the purposes of genealogy. That they originate in a man and are passed to all male lineage descendants, we know they didn't exist in prior generations, and that they originated in a specific man, whether we know his name or not. In the above hybrid tree, the R1b-BY172987 haplogroup rules above all testers. To date, we have two subclades, BY172985 and FTC78300. Additional branches may be found, but these represent specific men. Who?
For example, there are pre-FTC78300 generations and post-FTC78300 generations. So far, we don't know just where that line exists. Because descendants of two of Mark Bennett's sons had the SNP, then Mark had it. (They didn't spontaneously mutate in both sons.) But was Mark the first born with the marker or did his father have it? We don't know yet. To do that, a descendant of one of his brothers needs to test. Determining that will be critical to tying in additional lineages.
It's a similar story with BY172985. If we learn that James was the first in the lineage to have it, then everyone with that marker is descended from James. But the presence of the SNP would be far more inclusive if his father also had it. When properly placed on a tree, SNPs become a perfect ancestor predictor — no, the perfect ancestor determiner. This is where we're going.
Note that in the case of FT200461, found in the lineage of James Littleton Bennett, the names above him greyed out. My understanding is that the lineage is speculative. Here's my take on that.
The power of Y-DNA is that it can go beyond speculation. It can, with absoluteness, prove lineages. Not all lineages, mind you. That could be done only if every man was born with a "birth" SNP, a marker unique to male birth and is as unique as fingerprints and passes into the future forever. Instead, SNP mutations come along only every now and then. They're random and refuse to announce themselves. But when it happens we have gold, a marker that produces an exact Y-DNA print, the latest mark on the trail straight up the tree, and even through every part of the globe the lineage encounters.
When it comes to the "downstream" lineages for Mark Bennett, I've read a bit recently about the current "theory." SNP trees are about fact, not theory. For this reason, only the MRCA or EKA is listed above each tester in the main SNP tree. The markers listed above the name are facts (even if it's later decided the name is wrong). No speculation. The SNPs are right. And this is strictly the case for the bare bones Quick Tree. It's a summary of the genetics but not of the genealogy. It's accurate while not meant to be representative of a generation by generation genealogy. We could do that if every man had a unique SNP. Instead, we go with what we have.
Genetics and genealogy are two entirely different things. But they overlap. Like a Venn diagram, it's the shared portion we're looking for. The Blackwater hybrid tree illustrates that, but only to the extent that the genetics has revealed itself. Although the tested lineages so far are not rich in SNPs — unlike other groups I work with — we're far from being done. Only a tiny percentage of the potential output has tested.
It takes a lot of work to make Y-DNA "converts," so to speak. Ancestry.com has much to do with that. They don't tell their customers that autosomes, as great as they are for what they do, are not great for surnames studies. They promote neither the Y-DNA nor the MT-DNA because they aren't among the products they sell. (They once did but found better marketing potential with autosomes.) FTDNA was the very first to come into the market in 2000. Unfortunately, they don't get the media attention commanded by Ancestry. The results is that genealogists and family tree enthusiasts are largely ignorant about Y-DNA.
In brief, most autosomal users do not understand the Y. In fact, Y genetics is far more straight-forward. The Ancestry interface makes autosomes look simple, but they're not. Autosomal inheritance is extremely complicated. The situation is made worse by the way Ancestry links the DNA to the genealogy. Anything goes to the extent that anyone can make up ancestors. (It's not that blatant of course, but the result is largely the same.) Not are many lineages not sourced, many are simply unknown. And this leads to the unfortunate misconception: "I match with so-and-so and, therefore, his Johnson ancestors are my Johnson ancestors." In fact, that's often false. But if two Hart testers share SNPs, they are, in fact, of the same Hart ancestors. Autosomes can't do that, but the Y does -- as long as there are matches. And that's the really big caveat.
Furthermore, Y-STRs can tell us only so much. Because they can go both up and down in value, we don't have a clear picture of what values the former ancestors had — very unlike SNP mutations. They're great for grouping into general categories, but trees cannot be produced from them. So, if you want your lineage on the tree, the best thing to do is to upgrade to the Big Y. FTDNA's present sale continues to the end of the month. It's a good time to upgrade. The present rate for the Y-111 to Big Y upgrade is $229.
There's another way to figure which branch of the world-wide SNP database you belong to — individual SNP testing. That can be done at YSEQ.net for $18. Please contact me if you have any questions about it.
I'll leave it there for now. If you have Y genetic results to share, please do so. If you're a tester and have a lineage to share, please email me. And if you have any questions about any of this, I'm open 24/7.
Best,
Michael Cooley