The usual biochemistry that makes neurons go, as far as I know, is not unique to humans and has been stable for quite a long time.
But I think we’re getting a bit confused and start to chase our own tails. Let’s circle back and see what the original disagreement was.
You said that “intelligence is metabolically expensive, and it seems likely that it shows some fairly steep diminishing returns in a subsistence farming environment”. I countered by doubting that there’s any metabolic difference (cost) between an IQ130 and an IQ70 human—implying that while the returns are diminishing, the cost doesn’t change in the range we’re talking about. And after that it looks like the core of the discussion is whether somewhat higher intelligence (say, moving the average from 100 to 130) carries enough of a metabolic cost to make the evolution prevent that move.
My position is that the metabolic cost for IQ moves of a couple of standard deviations is sufficiently close to zero.
I would keep in mind that IQ differentials involving increased cranial capacity are more likely to have metabolic costs than ones that don’t. It also seems to me that most of the pressure against higher IQs is going to be cognitive rather than metabolic.
The usual biochemistry that makes neurons go, as far as I know, is not unique to humans and has been stable for quite a long time.
But I think we’re getting a bit confused and start to chase our own tails. Let’s circle back and see what the original disagreement was.
You said that “intelligence is metabolically expensive, and it seems likely that it shows some fairly steep diminishing returns in a subsistence farming environment”. I countered by doubting that there’s any metabolic difference (cost) between an IQ130 and an IQ70 human—implying that while the returns are diminishing, the cost doesn’t change in the range we’re talking about. And after that it looks like the core of the discussion is whether somewhat higher intelligence (say, moving the average from 100 to 130) carries enough of a metabolic cost to make the evolution prevent that move.
My position is that the metabolic cost for IQ moves of a couple of standard deviations is sufficiently close to zero.
I would keep in mind that IQ differentials involving increased cranial capacity are more likely to have metabolic costs than ones that don’t. It also seems to me that most of the pressure against higher IQs is going to be cognitive rather than metabolic.