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?
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...
As for the mtDNA only passed from mother to child, the Y chromosome is only passed from father to son.
If the equivalent exercise could be made on the male line resulting with a match of a known male descendant (if any exists). Then by cross correlation mtDNA/Y-DNA, we could be very close to ensure that the squeletton belonged to a son of a couple having the same mtDNA/Y-DNA combination than the mother and father of Richard III ...
.. we are left, however, with the very low probability (still not null indeed) that their exists another couple with the same mtDNA/Y-DNA combination (like the sister of the mother and the brother of the father) ...
hi there
I may be of interest to you as have been working on studies of the DNA
of Royalty and King Richard III DNA profile is to be compared on the YDNA side
his fathers father mtDNA I will be doing a study at a later date
anyway as I like to take a break and answer question I can help
right you need to make yourself a DNA family tree of the person you wish to
have tested in this case Richard III
next add to it his descendants above him so father and mother then for his father and also his mother and so on as far as you can on both sides of the DNA tree
Keeping males of the person being tested one side and females the females on the other so on the out sides you will normally have your father your fathers father his father and so on the same with the female only with your mothers mother and her mother and so on
this is a too which you can use later to find a set DNA line
right I should look like a large V shape if you where to draw an outline on each side
ok now Y DNA follows the fathers side and mtDNA the mothers side.
males have both YDNA and mtDNA
yet for a male he will have his fathers side YDNA and his mothers mtDNA yet will he have his fathers mothers DNA the answer is no and the same for his mothers Fathers Y DNA the answer is no
so you can only test the out side of the V DNA family tree as in your fathers fathers DNA the male line and your mothers mtDNA your mothers mothers line
so if an ancestor is connected to your fathers YDNA line fathers fathers the out side of the V DNA family tree yes you could find a DNA markers match you need 10 matching markers in a court of law and the same with your mothers mtDNA
right so what if you wanted to be traced to a pacific person say your grate grate grand father on your mothers side you Know testing your self for Y DNA to match his will be pointless so in this case you will need to test your mtDNA to trace it back to your grate grate grand mother and then you will need paper work such as marriage cert and birth certs to connect grate grate Gran father to grate grate grand mother and her to her daughter.
hope this helps