[Kudzu_Bob]

The average IQ produced by natural selection depends on the environment. There is no ideal level of intelligence apart from environment. If the Earth had a uniform climate, terrain, and so on from pole to pole, this presumably would not be the case.

[lutusp]

> If the Earth had a uniform climate, terrain, and so on from pole to pole, this presumably would not be the case.

I think that would also produce an optimal IQ, just a different one. But all IQs, indeed all traits of living organisms, ultimately derive from the degree to which they contribute to fitness.