Richard III and DNA evidence
Today's exciting news is that researchers from the University of Leicester have concluded that the remains of a body found under a car park in Leicester is that of King Richard III.
There are many pieces of evidence that point to this, one of which is that DNA extracted from the skeleton matches the DNA of modern descendants of the king. I am a little puzzled here.
The genealogy of royal families tends to be quite well documented, so I have no trouble believing that the modern descendants really are descended from Richard III. While I haven't read the details of the DNA analysis yet, and am relying on what I saw in the press conference, I'm also happy to take it as being reasonably well established that the similarities between the DNA of the skeleton and the DNA of the modern descendants of Richard III were sufficient to allow a conclusion that the skeleton found in Leicester was indeed an ancestor of the modern descendants.
So that proves it must have been Richard III, right?
Er, not really. Perhaps I'm missing something (and I should stress that I'm certainly no expert in genetic genealogy), but surely any modern day person would have literally thousands of 15th century ancestors. You have 2 parents, 4 grandparents, 8 great-grandparents, and so on. When you go back over 500 years, that's a lot of ancestors.
Now, if I were to do some quick back of the envelope calculations and point out that 500 years is roughly 17 generations, and 2 to the power of 17 is 131,072, you would rightly criticise me for making the assumption that there is no in-breeding, which becomes ever more implausible as you go back successive generations. While it might be quite rare, and ineed rather frowned upon, to breed with your 1st cousins, I imagine it's actually pretty common to breed with your 6th cousins. So obviously the actual number of ancestors would be a lot lower than 131,072. But surely it would at least number in the hundreds, if not the thousands?
I appreciate that the analysis used DNA from both maternal and paternal lines, and that would narrow down the pool considerably. But surely it still wouldn't point to a unique individual after so many intervening generations, would it?
I am puzzled about why researchers seem so confident in saying that DNA analysis proves that the skeleton belonged to Richard III, when as far as I can see, all it proves is that it belongs to one of a group of people who may have numbered in their thousands.
This is not to say, necessarily, that I don't believe the skeleton was actually that of Richard III. There were many pieces of archaeological and historical evidence, of which the DNA was just one part. Perhaps the overall picture is convincing enough anyway.
But I remain puzzled as to whether the DNA evidence really is as strong as it's made out to be. Now, as I say, I'm not an expert in genetic genealogy, so perhaps I'm missing something important here. Is there some crucial technique that genetic genealogists use that I'm not aware of, or is the DNA evidence really as weak as I suspect it is?