Are the Cornish a different race?

Having read over the weekend how the Cornish have failed in their attempt to have rude jokes about them stopped in law. I bring you this justification that they are no different to you or I.

• According to some American academics, the Cornish are racially distinct because they are descended from two Celtic tribes, the Dumnonii and the Cornovil.

This is hogwash, of course. A young man born in 1975, say, is descended from two parents. Those parents were probably born about 1950 to two sets of parents, so our young man is descended from four grandparents. He has eight great-grandparents born around 1925, and 16 great-great-grandparents born in 1900. If you keep going at a rate of four generations per century, by the time you get back to the year 950 (shortly after King Athelstan decided that civilisation began at the Tamar) our young man has 4,398,046,511,104 ancestors, which is about eleven thousand times the population of the entire world at that time.
What this probably means is that we are all related and share a common ancestry, and to talk of any one group of people (the Corns) being descended exclusively from any other group of people (the Dumnonii and the Cornovil) is complete and utter rubbish. Mind you, it's a rather unsettling thought that I am therefore related to, say, Jade Goody. And don't tell me I shouldn't pick on her because she's dead. Most of my ancestors have been dead people. Many of them still are. What is this spurious sensitivity about dead people? Does being dead make you a better person?