4 ms·

> I'd tend to assume that any genetic trait that improves intelligence without significant drawbacks would spread rapidly through interbreeding... I would agre

> I'd tend to assume that any genetic trait that improves intelligence without significant drawbacks would spread rapidly through interbreeding... I would agree if we were confident that greater intelligence was always worth it, no matter the metabolic cost. Brains are expensive! Making them bigger incurs additional metabolic costs (and potential complications in the developmental phase). It's very possible that another 20 IQ points wouldn't have really made humans better hunter-gatherers, but would've meant they had to eat more. Granted, there are likely other ways to get smarter, but it's possible that there would be other systematic tradeoffs required.

Symmetry 9y ago
Brain size is certainly an issue but from my understanding it's more about the constraints of childbirth than metabolic cost that are restraining it. When you're resting flat on your back your brain uses up 10 of the 100 watts you're dissipating but the variation in brain size given other constraints is pretty low and I'd expect plausible power differences from that to be pretty small too. And brain size only has something like a .3 correlation with IQ so other factors like efficient myelination or organization are probably much more important. I'd expect better myelination to reduce energy consumption if anything. As to organization I'm too unfamiliar with the scaling laws of neurons to be sure but I'd suspect brain organization that increased intelligence at least wouldn't increase energy usage much. So I'm still inclined to view intelligence as being constrained, evolutionarily, by issues of complexity rather than tradeoffs between efficiency and effectiveness as with height.