It was the new film, Into the Storm that started me thinking. Brendan Gleeson plays Winston Churchill and has commented widely on how ironic it is that an Irish actor is in the role. I recalled the rumours that Churchill fathered Brendan Bracken (a red-haired Irish-born MP and wartime Minister) and the fact that he too had red hair in his younger days. This is almost always the result of a Celtic gene but how exactly does it behave and where did it originate in his case?
Bill, A Scots-Canadian Ricardian, pointed out that his daughter has red hair but neither he, his parents nor grandparents did although his maternal great-grandfathers did. I searched for Churchill on Genealogics and looked back four generations (as with Bill). No given ancestor sounded demonstrably Scots or Welsh whilst the Irish peers listed could have been English in their descent. I stepped back slightly further and found two Scottish Earls, which potentially answers the first question.
Bill suggested that most people have a common ancestor within ten generations – one of 1024 – but there is an obvious flaw here. People, particularly the nobility, tend to intermarry so we have fewer unique ancestors to compare. If the theory really did apply, cubing that number to about 1.073 US billion would cover thirty generations or 750 years – back to Henry III’s struggles with de Montfort – to exceed the then population of the world. Because of duplication, we would need to go back further to pre-Conquest days or Alfred’s childhood.