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?
I have two words for you – mitochondrial DNA (well, technically one word and one abbreviation).
The press release is talking about tracing the maternal line, which is the clue to them relying on mtDNA evidence. Mt DNA is passed on exclusively by the mother (sperm mitochondria stay in the tail) and undergoes far less mutation than autosomal DNA, so can show an unbroken female line of descent. Had the mtDNA not been a match then the skeleton and the current-day donor would not have been related (either because the skeleton wasn’t Richard III or because the donor got his genealogy wrong, or both).
This DNA evidence shows that the skeleton and the donor have a common female ancestor.
Jackie
Hi Jackie
I dare say we know the skeleton and the donor have a common female ancestor, but that doesn’t narrow the skeleton down to a single individual, does it?
I appreciate that mtDNA is only transmitted through the maternal line. But that means that as well as sharing our mothers’ DNA, we also share our maternal aunts’ DNA, and the DNA of all sorts of other women (and their sons) branching off various bits of our maternal lines.
So yes, if the mtDNA hadn’t matched, then we would know that the skeleton wasn’t Richard III (assuming the genealogy of the modern donors was correct). But I don’t think we can draw the reverse conclusion, can we?
mtDNA is only ever maternal, so sons don’t ever come in to it as far as mitochondria are concerned (sorry, I’m married to a mitochondrial geneticist – something must have rubbed off over the years).
You’re right, however, that the only inference from this piece of evidence is that the two individuals share a common female ancestor. If that individual happens to be Richard III’s mother (as the Leicester researchers suggest (Cecily Neville – see http://www.le.ac.uk/richardiii/science/extractionofdna.html) then it would be a reasonable assumption that the skeleton is one of her sons. If it was his grandmother, then we start moving into sons plus cousins, and so on. But there’s no way of telling what generation prior to the skeleton that female belonged to.
So no, the DNA evidence does not prove that the skeleton is Richard III. It could easily be a cousin or second cousin etc. I’m sure Channel 4 will give us a full explanation at 9 pm tonight…