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Neanderthals had larger brains than us, so nature definitely didn't hit a hard limit on how large ours could physically be. Yes there are costs to a larger, mor
by jjk166 6y ago
Neanderthals had larger brains than us, so nature definitely didn't hit a hard limit on how large ours could physically be. Yes there are costs to a larger, more powerful brain, but up until us those costs were justified by the benefits of increased intelligence. More intelligent apes could better raise children, relied less on running quickly, and could acquire more food.
Somewhere close to our current level of intelligence, the benefits of increased intelligence stopped justifying further improvement. The question is why here?
Birthing issues seems like a particularly weak explanation, given than that the negatives of bigger hips scale with the radius of the head while the benefits of intelligence scale with the volume - the more intelligent we get, the more it makes sense to keep making the skull larger. With increasing skull size, there is no need for babies to become any less functional. Calorie demands should scale linearly with intelligence, so it's possible increased intelligence doesn't help a hunter gatherer acquire more food beyond a certain point, though given how much food production has been increased through ingenuity this seems unlikely to be the case.
- danielheath 6y ago> negatives of bigger hips scale with the radius of the head Implying linearity here is ridiculous. The increase in force applied to the hip joint scales with the radius of the head; cartilage gets damaged if you apply too much force but will last a lifetime if you don't. > the benefits of intelligence scale with the volume That's completely unsupported. Firstly because the number of brain cells scales with the volume, but there's no evidence that larger brains in humans are associated with higher intelligence (then again, most mutations are negative), and secondly because it implies a linear relationship between 'amount of intelligence' and 'amount of benefit'. > given how much food production has been increased through ingenuity this seems unlikely to be the case This has not happened on evolution-relevant timescales. There was famine in eastern Europe only 50 years ago. People died of hunger because their calorific needs were not met - selection pressure towards surviving famine has not stopped.