Newton, Euler, Darwin, Einstein, Paul Dirac, Richard Feynman… Our modern world wouldn’t exist without them. Look up estimates of their IQ. Read some of their work and try to imagine having the same level of insight and producing similar volumes of it if you devoted every waking hour to the task.

Then read up on the ancient Greeks. Even after 12 years of education most modern people wouldn't be able to measure the circumference of the Earth like Eratosthenes did hundreds of years before Christ. The ancient Greeks were pretty darn smart.