Ezra Klein points out today that Mark Zuckerberg wasn't responsible for the invention of social networking. Technology had made the idea possible, and lots of people were doing it:
This is a rather common phenomenon: It's called "simultaneous invention," and it happens all the time: Technology advances to the point that the next step is obvious to multiple people, and so they all take the next step at approximately the same time. In the end, one of them gets the patent, or the market share, and so squeezes the other out and becomes synonymous with the invention. That's what happened with Alexander Graham Bell, who in all likelihood invented the telephone after Elisha Gray.
Go to London and ask someone on a street corner who invented the light bulb, and if you're an American you'll probably be surprised at the answer you'll get. Likewise, Darwin and Wallace conceived of natural selection at about the same time, Newton and Leibniz both invented calculus, and huge masses of inventors were responsible for automobiles, airplanes, and computers.
But here's a question I've never taken the time to research properly: what inventor was most ahead of his time? That is, which one invented something important that was so out of the blue that it probably would have been decades or more before someone else invented it if he hadn't? Let's limit this to the past few centuries and actual working products, not just sketches and descriptions. I don't really have any good candidates here, though I suppose accidental inventions like penicillin might be in the running. How about Isaac Newton's invention of modern mechanics? Was anyone else close to that when Principia was published in 1687? Any other nominees?
UPDATE: So far, the leading contenders in comments are Einstein for the General Theory of Relativity and Tesla because — well, you know, Tesla.
Of course, I was a little slippery about whether only physical inventions count, or whether theoretical discoveries also count. Maybe we need two different categories? In any case, General Relativity seems to have a lot of support in the theoretical discovery department.