Observe the large variance in ancestry of Diana’s two third cousins presumably derived from Eliza Kewark (though there is always the chance that these segments come from different South Asian ancestors, the typically South Asian mtDNA match across the two reduces the probability of that being the answer in this case). Beyond eight generations the chance of a genetic segment being passed from an ancestor down to a descendant is small. Diana’s cousins are seven generations down from Eliza Kewark, so it isn’t totally implausible that a segment should get passed down. But William at eight is at the boundary, and he may carry no segments (in fact, Diana may have carried no segments). Of course I did note that their mtDNA is likely to be passed down, because there is no element of chance in that. You have your mother’s mtDNA. But one can debate whether mtDNA, which is not present in the nucleus, really counts as ancestry. I believe that heritable genetic material is heritable genetic material. Assuming the lines of descent are as they are recorded I accept that we know for a fact that William likely has South Asian mtDNA. But we most certainly do not know if he has any South Asian autosomal DNA.
But in the end how much does this matter? People will make of it what they will. And yet there is an important aspect to note: this seems like another instance of the firm BritainsDNA hyping genetic findings to increase their profile. You see that the screenshot of their website shows that they’re promoting the story about William’s ancestry, and, they’re also claiming that they are offering the world’s most advanced genetic ancestry test. First, I have to observe that their price points are very high, and second, if they are going to claim the most advanced test in the world they should actually do a point-by-point comparison with other services, which they don’t seem to do.
Perhaps more importantly this outfit now has a history of getting caught up in, and frankly stoking, hype. I don’t begrudge anyone their livelihood, or financial success, but scientists do have an implicit and explicit honor code. Jim Wilson has been involved in some interesting work, which is what I knew him from. But a third time will be a trend, and Wilson shouldn’t be surprised if rather soon he becomes thought of as a ‘tabloid geneticist,’ rather than a scholar who popularizes serious science to the broader public.Addendum: For American readers I should make it clear that it isn’t totally surprising that the British upper classes and gentry have some Indian ancestry, because so many of them have had ancestors associated with the British Raj. The book White Mughals explores this period and people in extensive detail. For some specifics, recall that Robert Jenkins, later Lord Liverpool, and Prime Minister of the United Kingdom for 10 years, 1817-1827, was 1/8th Indian by ancestry. The British actress Nicollette Sheridan is also 1/8th Indian. And finally, my friend Dan MacArthur clearly has South Asian ancestry, due to the same historical circumstances as the individuals above. This is perhaps the British equivalent of “Native American ancestry.”