I originally wrote this article for my too-neglected private family tree site. However, given how little information there is out there about genetic genealogy in general, and our R1b1b2a1a1d1* haplotype in particular, I'm making this public in case anyone else with this haplotype might benefit from my historical analysis, or chime in with corrections or counter-theories, in case my own interpretation becomes obsolete.
Thanks to my brother purchasing a genealogical DNA test, we now know something about the direct paternal ancestor of James Craven (born 1806 in Leeds, Yorkshire, England), which should be of interest for any of his descendants. Exactly what we know, though, takes a little unpacking.
Concretely, we know that he was of the Y-DNA haplogroup R1b1b2a1a1d1*, previously known as R1b1c9. This is not atypical for an Englishman, but since "the English" as a race are a mix of Celtic Britons, Germanic Anglo-Saxons, and Norse Vikings, what we would really like to know is which of these origins R1b1b2a1a1d1* points to. Unfortunately, there is no clear-cut answer (that I have found).
Y-DNA testing tests sequences on the Y-chromosome, which is (of course) only present in males, and therefore every male's Y-chromosome-specific parts only come from his father. So, the mutations that mark different populations are only those present in the direct paternal ancestor.
It is rather exciting, being able to know something concrete, if obscure, about your direct paternal ancestor who lived thousands of years ago. However, we must remember that the genetic tests don't tell us anything about any other ancestors (which number in the hundreds or thousands when you go this far back). So that's a first caveat.
For instance, in my case, although this test shows that our paternal-line Craven ancestor had no Irish origins, four of my eight great-great-grandparents (all the women, as it happens) came from Ireland, so I almost certainly have more Irish blood than English, overall, even though it is invisible on this DNA test. (To get a full picture I would have to find a male direct paternal descendent of each of their fathers, and do a Y-DNA test on them; unfortunately I haven't even uncovered who their fathers were yet, let alone whether they have any surviving male descendants!) Forming a more complete genealogical family tree, then, requires enlisting male cousins descended from as many of your other ancestors as you can find. So this discussion only concerns my direct patrilineal line.
So how far back are we talking about with this test? That's the second caveat: scientists are still debating a lot of this. It all depends on when the mutation that makes this haplogroup distinct from that haplogroup occurred, but knowing this is difficult, and the best scientific opinion could change a lot as this new field advances. So what I say now about R1b1b2a1a1d1* might be considered total bunk in fifty years, or even five.
But according to the best estimate as I understand it, this mutation occurred around 2,900 years ago, but it could have been as much as 10,000 years ago. In either case, it is very important to realise that this is before recorded history in the part of the world concerned. Therefore, trying to associate our haplotype with a particular Germanic tribe is a fool's errand: the most ancient names of Germanic tribes that have come down to us today are still too new to be associated with one particular haplotype.
On the bright side, though, between then and when recorded history starts, people weren't likely to have migrated all that much, so we can still make some educated guesses.
In prehistory, then, this haplogroup is concentrated around Northern Europe, over a zone covering the north of the present-day Netherlands, Germany, and the south of Denmark. The tricky bit is that until after the end of the last Ice Age, there was a place called Doggerland, connecting Britain to the continent. Apparently it was a good place to hunt mastodon back then, but today it sits at the bottom of the North Sea! (There's one ancestral homeland I won't be visiting.) The significance of this is that, as Doggerland gradually filled in with water, some populations presumably ended up on the north shore, in Britain, and some on the south shore, in continental Europe—among the people who would become the Anglo-Saxons, and end up conquering Britain around AD 600 when the Romans left. So if the mutation occurred before Doggerland disappeared, we wouldn't know for sure whether our ancestor were a Briton or an Anglo-Saxon.
However, it is also quite possible that the mutation took place after Doggerland was already underwater. In this case, the native Britons would not have the R1b1b2a1a1d1* haplotype, and we would know that our ancestor, since he did have it, was an Anglo-Saxon. It is tempting to believe this version since it is more definite, and for that reason a lot of genealogists on the internet are likely to hold by it. Just remember that it might turn out to be inconclusive.
In either case there is a third possible outcome: the R1b1b2a1a1d1* area overlapped with southern Denmark, as I mentioned above. The area inhabited by the Anglo-Saxons before they came to England bordered the land inhabited by the Danes, who invaded England in turn a few centuries later. Since the genetic marker could be present in either population (being far older than either), it is possible that our ancestor might have come to England much later, with the Viking invasions (circa AD 900), and settled there then. Statistically this seems less likely than the Anglo-Saxon option (and Cravenshire is pretty far inland), but we can't know for sure.
My own opinion, then, is that the Anglo-Saxon origin seems the most probable, but that is based on my limited understanding of the numbers of people involved in each population movement. I could be wrong about the probability, or even if I am right about that, our ancestor could fall in a minority case, and there is no way to know.
We know approximately where our paternal ancestor lived in prehistory, through the test, and we know where our ancestors lived in the 1700s through our recorded family history—and we know that there were three historical migrations that would account for how our ancestors got from their starting point, near the present-day Netherlands, to Cravenshire, in the intervening millennia. But genetic genealogy can't tell us which of the three likely scenarios actually happened.
Still, even knowing the scope of possibilities is more specific than it would be otherwise: it still gives us a far clearer picture than if we had no idea of his haplotype. Some Englishmen have ancestries that point to Celtic, Roman, Norman French, Pictish, and Swedish ancestries, to name a few, and at least we can rule all of these out for our ancestor. (Our direct patrilineal ancestor, anyway.) Since Cravenshire was originally settled by Welsh tribes, eliminating the Celtic hypothesis does give me a more concrete picture of my family history.
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There is also a DNA test that tells something about the maternal line, looking at the mitochondrial DNA, which is passed from mother to child unmodified, and so gives info about the maternal ancestor (in this case my great-grandmother Ruth Leary's mother's mother's mother, etc.). This was a lot less informative, though, because the mtDNA group, Pre-HV, is such an early mutation (circa 25,000 to 50,000 years ago) that it can be found in nearly any Caucasian person. But I record it here for the sake of anyone else descended from the same maternal ancestor. Unfortunately, though, the mtDNA test doesn't give a lot of information with which to speculate on the family history of one's matrilineal ancestry.