why would being born in the current century preclude one from making fundamental contributions?
You are making a common mistake of assuming that just because someone is good at something like programing computers the same skill would translate identically to a completely different domain.
If anything he is lucky to have been born in an era where his skill of programming computers could be put to use - otherwise his talents may have gone to waste, he may have ended up toiling fields his talent untapped and undiscovered, like that of millions before him.
He's "good at programming" like Galileo was "good with telescopes." Computers, telescopes, hammers, they're all just tools, and Carmack has proven himself as far more than just a handyman.
He's the kind of person where, if you show him what you're working on and he doesn't understand it, you probably need to go back to the drawing board.
Cult of personality much? Don't get me wrong, Carmack is one of a kind. But seriously, "if Carmack doesn't understand your idea => your idea is hopeless" -- this can not be healthy.
EDIT: I'll elaborate a bit. In my experience in both industry and academia I've witnessed numerous occasions when brilliant people would get things wrong, ignore a brilliant idea, follow a hopeless research direction, etc. etc. Authority matters, but _nobody_ is flawless.
Your argument is a bit like: here is this amazing long-distance runner who trains for years at a time, had he put all that effort into painting he would be a new Picasso.
For what is worth computers are unique tools unlike any other tool that mankind has invented before - thus it is much harder to tell what other jobs would a good programmer excel at.
John in particular has shown a propensity to translate his skills into disjoint domains pretty well. I don't think he's good at what he does because he's good at computers. I think it's more that he's really really good at understanding problems and designing reasonable paths to solutions.
And then he has the ability to power through learning what he needs to in order to build toward those solutions lightning fast.
High intelligence in one technical domain translates well enough to competence in other technical domains. Carmack isn't just a programmer, he is a highly creative technical problem solver. However, AGI does seem orders of magnitude more complex than developing 3D game engines.
You are making a common mistake of assuming that just because someone is good at something like programing computers the same skill would translate identically to a completely different domain.
If anything he is lucky to have been born in an era where his skill of programming computers could be put to use - otherwise his talents may have gone to waste, he may have ended up toiling fields his talent untapped and undiscovered, like that of millions before him.