It hit me recently why I dislike such arguements. They assume unchanging human capability.
A 1800's medical doctor wouldn't have the same skills as a 1900's doctor - not just in medical knowledge, but more importantly, in the ability to change. It's common nowadays for technical professionals to "need to keep up" - something that wasn't anywhere near as critical in the not-too-distant past.
I'm blathering a bit here, but the long and the short of it is that as humans are challenged, humans adapt. As humans adapt, there's greater forces leading to greater changes. As changes increase, so does the amount of challenge. And we have a self-reinforcing spiral...