These questions make others like p4p tough, too.
You throw a guy from today back into those circumstances you also have to dial back his access to the knowledge of the sport, SnC, and diet. With those limitations, these modern guys wouldn't have their distinct advantages. Boxing started out in a raw and imperfect way - which is ironic since it was called a sweet science (if they only knew what we know today, right?). Anyway, I think boxing knowledge peaked in the 40's and 50's. I say this because all the stuff we know today, they knew in those decades. However, they were also, better infighters back then - and that's not because of the black and white footage either. They were just better at it, more often than not. They had smaller gloves, so they learned head movement defended with their forearms out and parried more with their open hands. They also fought more and weren't as carefully matched as they are today. Take away tape, and they had to learn on the fly more. Those things make me think that fighters - particularly from the peak years of the 40's and 50's - would have an advantage as far as instincts, intuition, and overall ability. You take the very best from today and send them back, they would probably do pretty well, but we simply don't have as many that would be as good. The depth was there simply because more people fought back then. There was also only one belt, so that makes the conversation deepen a bit, too.
But, if you just chuck a guy from today into a time machine and throw him back, then different, impossible things happen.
