IDK about all that, maybe those individuals you mentioned would have been even greater if they had all of their faculties intact or maybe they may have been even better if those abilities were enhanced. If you simply look at society today, you can see how far back we fell by keeping ideas about improving ourselves in the dark, even as far as calling improving people "racist" or "evil". It seems that human IQ is lowering at a staggering pace, that that is partly due to breeding. If the dumbest, most useless people continue to reproduce, Society will fall.