As pointed out by others, the atomism of Democritus is not a solid theory, but a blue vs. green position. One fellow thinks that if you divide something repeatedly, you'll never stop being able to divide it; another fellow disagrees with him, they come up with elaborate verbal justifications for their positions.
So why don't we consider some Greek theories that were actually solid theories? Aristarchos argued that, since the sun was so much bigger than the Earth, it made more sense for the Earth to orbit the sun than the sun to orbit the Earth.
Other mathematicians thought about this theory, and eventually responded with, "well, if that were true, we should expect to see parallax effects on other stars. We don't, so either everything orbits around the Earth or the stars are unimaginably far away."
Well, it turns out that the stars are unimaginably far away, and so the parallax effects are too weak to see with the naked eye. But the Greeks had their priors in the right place for the evidence they had access to.
Likewise, things like natural selection (as we understand it) and intelligence explosion don't seem like they're obvious without evidence to back them up, and could be reasonably dismissed without that evidence.
People here routinely make statements regarding the universe about which the available evidence is still inconclusive. If we care about the accuracy of such claims it seems worthwhile to pay attention to the how such statements worked out in the past.
Also see: History of the Friendly AI concept.
The ancient atomists reasoned their way from first principles to materialism and atomic theory before Socrates began his life's work of making people look stupid in the marketplace of Athens. Why didn't they discover natural selection, too? After all, natural selection follows necessarily from heritability, variation, and selection, and the Greeks had plenty of evidence for all three pieces. Natural selection is obvious once you understand it, but it took us a long time to discover it.
I get the same vibe from intelligence explosion. The hypothesis wasn't stated clearly until 1965, but in hindsight it seems obvious. (Michael Vassar once told me that once he became a physicalist he said "Oh! Intelligence explosion!" Except of course he didn't know the term "intelligence explosion." And he was probably exaggerating.)
Intelligence explosion follows from physicalism and scientific progress and not much else. Since materialists had to believe that human intelligence resulted from the operation of mechanical systems located in the human body, they could have realized that scientists would eventually come to understand these systems so long as scientific progress continued. (Herophilos and Erasistratus were already mapping which nerves and veins did what back in the 4th century B.C.)
And once human intelligence is understood, it can be improved upon, and this improvement in intelligence can be used to improve intelligence even further. And the ancient Greeks certainly had good evidence that there was plenty of room above us when it came to intelligence.
The major hang-up for predicting intelligence explosion may have been the the inability to imagine that this intelligence-engineering could leave the limitations of the human skull and move to a speedier, more dependable and scalable substrate. And that's why Good's paper had to wait until the age of the computer.
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