If David Skalansky did not exist, would we be forced to create him?

And by this, what I really mean to ask is, is it possible that any scientist, statician, 'founder' of any idea, concept or device did not exist, would it be possible that their idea, concept or device would never exist? Is Newton neccessary? Or Eucilid? Or Marx/Lenin/Adam Smith/Keynes

Also, how much were these men a product of their times and the stage in scientific thought at the moment, and how much were they 'ahead of their time'?