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In order to get brains as big as we already do, biology has us: * Birthing prematurely compared to other species (most species live young are functional at bir

In order to get brains as big as we already do, biology has us: * Birthing prematurely compared to other species (most species live young are functional at birth) in order to fit the brain through the hips. * Permanently reducing the mothers top speed (wider hips means the joints are exposed to higher forces while walking). * Requiring 5% or so more food. All three of those have been serious impediments to human survival for most of our existence, and provided a counter-pressure against improvements in biological intelligence. In the past century, the Haber-Bosch process has meant we can reliably grow enough food without pursuit hunting. Without that counterpressure, evolutionary improvement seems very likely, but will take hundreds of thousands of years without genetic engineering or eugenics (neither of which seems like a good idea to me).

mantap 6y ago
Intelligence has a strong nurture component that we call education. It's unclear what good, if any, better genetics would do. We are already capable of reproducing and outsourcing many of the brain's functions to computers, and it seems likely we will reach the AGI endgame within a century or two conservatively. Arguably we have far too much intelligence and will end up causing our own destruction.
Mumps 6y ago
FYI: the obstetrical dilemma isn't so strongly supported nowadays [0]. I can't find the study i'm thinking of at the moment, but at least one study proposes the early birthing in humans allows the brain extra social development. [0] https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0118903 https://journals.plos.org/plosone/article?id=10.1371/journal...
- danielheath 6y ago
  That link says wider hips don't slow down walking. However, women need hip replacements at a far higher rate than men. Given men are typically heavier one would expect their joints to wear out faster, but as alluded in my comment upthread, widening the pelvis means walking exerts a higher peak force on the hip joint due to increased torque, which is a plausible mechanism for it wearing out faster.
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.

mantap 6y ago

Intelligence has a strong nurture component that we call education. It's unclear what good, if any, better genetics would do. We are already capable of reproducing and outsourcing many of the brain's functions to computers, and it seems likely we will reach the AGI endgame within a century or two conservatively. Arguably we have far too much intelligence and will end up causing our own destruction.

Mumps 6y ago

FYI: the obstetrical dilemma isn't so strongly supported nowadays [0]. I can't find the study i'm thinking of at the moment, but at least one study proposes the early birthing in humans allows the brain extra social development. [0] https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0118903 https://journals.plos.org/plosone/article?id=10.1371/journal...

danielheath 6y ago
That link says wider hips don't slow down walking. However, women need hip replacements at a far higher rate than men. Given men are typically heavier one would expect their joints to wear out faster, but as alluded in my comment upthread, widening the pelvis means walking exerts a higher peak force on the hip joint due to increased torque, which is a plausible mechanism for it wearing out faster.

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.