Eliezer S. Yudkowsky, <sentience@pobox.com>, writes:
> If intelligence was that simple, rats would be sentient.
Consider the life of prehistoric humans. I don't see why someone marginally more intelligent than others will have much of an advantage in hunting or gathering. Most of what is needed is learned culturally, and those techniques have been optimized over generations to approximate local maxima. Sure, even ten or twenty thousand years someone domesticates a new animal or discovers fire, but these events are so rare they can't have any significant evolutionary input.
My feeling is that people stumbled onto some cultural and physical changes which set up specific incentives for greater intelligence - bipedalism, the use of spears, fire, tools, etc. This brought us up to IQ 100. But that was smart enough for these purposes. IQs of 130 or 150 wouldn't make someone any better at using these tools.
Hal