I don't know. I think the high intelligence of doctors has more to do with the fact that it's a very desirable occupation and so they can afford to only choose

I don't know. I think the high intelligence of doctors has more to do with the fact that it's a very desirable occupation and so they can afford to only choose the best applicants for medical school, not because it inherently requires great intelligence. I know several elderly and accomplished medical professors who claim that they would not have been accepted into medical school under today's conditions. They got in during a time when it was very much easier academically (but harder financially).