So, Benedict Cumberbatch, national treasure, is related to Richard III. His upcoming role as the infamous king in the next instalment of The Hollow Crown could not be more appropriate, and he is also to read a specially composed poem by Carol Ann Duffy at the reinterment service.
Widely reported in the press, it was the genealogical research carried out by my colleague, Kevin Schürer, that showed that Benedict is related to Richard III through Edward III (though some of the press rather erroneously stated that this relationship had been confirmed by a DNA test.
Unfortunately perhaps for Cumberbatch – I’m not sure how he feels about such things – DNA analysis couldn’t be used to prove Cumberbatch’s relationship. This is because of the way our DNA is inherited through the generations and the way he’s related to the former king of England through a mixture of male and female ancestors.
The vast majority of our DNA is a mixture of that inherited from our ancestors. This is actually quite straightforward to understand. Each of us inherits half our DNA from our mother and half from our father. They, in turn, inherited half from each of their parents: in simple terms you halve the amount of DNA you expect to share with a direct ancestor in each generation (provided there haven’t been any relationships between relatives in the genealogy). Richard III lived some 500 years ago and 21 generations exist between Richard and Benedict (through John of Gaunt, the shortest link between them). This means Benedict would be expected to share ~ 1/1,048,576 of his DNA with Richard through this relationship.
Alongside this there is a shuffling of DNA (known as recombination) which occurs before each of our parents passes down the portion of DNA we are to inherit. This means that we don’t necessarily inherit equal amounts of DNA from each of our grandparents. Over the generations, not every one of our ancestors’ DNA is represented equally – so it’s completely possible that Cumberbatch doesn’t share any DNA in common with Richard through his relationship to him.
DNA analysis therefore wouldn’t allow us to prove his relationship to Richard. From a scientific point of view, however, it would be interesting to see just how much DNA that Cumberbatch, and similarly distant cousins, do share with their famous relative to see if there are deviations from what we’d expect.
Crowning a king
So how, then, did we identify the king in the car park?
Fortunately for the purposes of identification in the Richard III case, there are two segments of our DNA that are inherited in a very simple way down through the generations: these are mitochondrial DNA and the Y chromosome.
Mitochondrial DNA is a small circular piece of DNA with a number of important functions. This is the segment of DNA which has itself become rather famous, the Benedict Cumberbatch of the genetics world perhaps, in the debate about three-parent families and mitochondrial disease. However, what concerns us for the Richard III project is the way it’s inherited: the DNA sequence is copied (with the occasional typo) and passed down by a mother to all of her children, boys and girls, in the egg. Only her daughters can pass it on.
The other segment of DNA which is useful for this project, though with its own set of issues, is the Y chromosome. This is a rather small chromosome that has on it a crucial gene known as SRY (sex determining region Y) which causes a foetus to develop as a male. As such, only men carry a Y chromosome and only men can pass it on. Again, it’s copied, with the odd little typo, and passed down to the next generation.
So not just any old relative could be used as part of Richard III’s DNA identification process. The only ones who could were living men or women related through an all female line to Richard. These would be expected not to carry Richard’s DNA (only Richard can carry his own DNA) but an identical, or near identical, copy of the mitochondrial DNA type that Richard had.
In this case, Michael Ibsen and Wendy Duldig, the two living relatives, and Richard III all inherited their mitochondrial DNA type from Cecily Neville, Richard’s mother. Michael and Wendy inherited through Richard’s sister, Anne. And we found a match.
Similarly, men related to Richard through an all-male line might be expected to carry an identical or near identical Y chromosome type, unless, of course, a false paternity had taken place where the biological father is not the recorded father. Going into the project, we knew that there was a possibility that this might occur: all that was required was one of the relevant ladies in the tree running off with a medieval milkman and the medieval milkman’s Y chromosome types would have ended up in the genealogy rather than the one recorded.
In the end, two false-paternity events were revealed. One must have occurred recently as one of the five male-line relatives (all with the surname Somerset) was not genetically related to the other four. Another must have occurred historically, between Henry Somerset (the common male-line ancestor of the remaining men) and the skeletal remains. This mismatch was simply built into the statistical analysis of all the evidence and did not affect the identification of the remains.
While only individuals related to Richard in either of these two ways could be used for the DNA analysis in the identification of Richard III, Cumberbatch will be by no means alone in being a distant cousin of Richard III. Richard III himself left no living descendants, but my colleague Kevin and, more famously, Radio 4’s More or Less estimate that there are something in the region of between 1m and 17m people alive today who are descended from any of Richard’s immediate family.
Again, this is easy to calculate. If one of Richard’s siblings had two children who survived to adulthood, who then went on to have two children and so on, over, for example, 20 generations (220), then this means that they would have some 1,048,576 descendants alive today (provided there was no intermarrying between relatives). If you allow for the average medieval family size of 2.3, then this results in 17,161,558 descendants. Cumberbatch himself is descended from Edward III, who was Richard’s great, great-grandfather, and so this will give Cumberbatch rather a large number of “cousins” who are related in a similar way to Richard III.
Indeed, we’re all related to Richard, it’s simply a matter of degree. What makes Cumberbatch different in this case, is that how he is related to Richard is known – the majority of his “cousins” simply don’t know their family trees. This will perhaps keep my son happy, a fan of Cumberbatch, to think that he is actually a distant cousin. But with so many cousins to write to, I think we’ll forgive Cumberbatch for not putting us on his Christmas card list.