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An essay on intelligence
Sep. 10th, 2007 03:05 amThis came up as an answer to a question in Another Place. It grew unnecessarily long. Some might find it interesting reading.
[Quoted: consciousness has been selected for by evolution. We have big brains and are conscious; therefore, big brains are needed for consciousness, because otherwise the brain wouldn't have got so big.]
Ah, hang on, false assumption in there. It's the /post hoc ergo procter hoc/ thing.
Yes, we evolved large brains because we needed large brains for some reason - this must be the case, because brains are "expensive". Fragile, slow maturation, vast resources drain, major problems with female pelvic architecture to get grotesquely enlarged heads of infants out, etc. etc.
/But/ there is no direct evidence that /consciousness/ is *why* we have large brains.
Counter-example: dolphins have very large brains for their body mass, too. (So, incidentally, do mice.)
But in dolphins, the evidence appears to be that they've got whacking great brains for reconstructing a coherent "view" of their environment out of sonar echoes, which is not a great medium for doing it.
Bats have it easier; they use sonar to avoid hitting things and catching and trying to eat anything small that's moving. Throw small pebbles in front of bats, they grab them and try to swallow them. They're not very discriminating and they live in an environment where sound travels poorly & they get relatively few echoes back. Plus, they can use smell too.
Dolphins' sonar is vastly more sophisticated than bats'. They can see inside objects and so on.
There is reasonably good evidence that lots of that brain mass is for auditory processing and resolving sonar impulses into shapes. It's their visual cortex, so to speak.
We have really big frontal lobes; AIUI, dolphins don't.
The real question is: OK, so we have big brains, but why?
It could be - I'm just throwing up some ideas here - that as our ancestors left the forests (or the forests left them), they grew terrestrial, into hunters, into tool-users, that they evolved big brains to allow more versatile behaviours in a broader range of environments than sylvestran apes. Proto-humans coped with desert, savanna, forest, riparian and coastal environments, with a habitat range from tropics to temperate zones, with hunting and gathering and tracking and following herd migrations, with memorizing what was and wasn't good to eat in widely differing habitats, with being able to throw rocks accurately, shape stone tools, all that sort of thing. All long before language. Indeed, the fossil record is scant in such fine detail, but it could be we evolved language *long* before we evolved sentience and language itself selected for big brains.
( Read more... )
[Quoted: consciousness has been selected for by evolution. We have big brains and are conscious; therefore, big brains are needed for consciousness, because otherwise the brain wouldn't have got so big.]
Ah, hang on, false assumption in there. It's the /post hoc ergo procter hoc/ thing.
Yes, we evolved large brains because we needed large brains for some reason - this must be the case, because brains are "expensive". Fragile, slow maturation, vast resources drain, major problems with female pelvic architecture to get grotesquely enlarged heads of infants out, etc. etc.
/But/ there is no direct evidence that /consciousness/ is *why* we have large brains.
Counter-example: dolphins have very large brains for their body mass, too. (So, incidentally, do mice.)
But in dolphins, the evidence appears to be that they've got whacking great brains for reconstructing a coherent "view" of their environment out of sonar echoes, which is not a great medium for doing it.
Bats have it easier; they use sonar to avoid hitting things and catching and trying to eat anything small that's moving. Throw small pebbles in front of bats, they grab them and try to swallow them. They're not very discriminating and they live in an environment where sound travels poorly & they get relatively few echoes back. Plus, they can use smell too.
Dolphins' sonar is vastly more sophisticated than bats'. They can see inside objects and so on.
There is reasonably good evidence that lots of that brain mass is for auditory processing and resolving sonar impulses into shapes. It's their visual cortex, so to speak.
We have really big frontal lobes; AIUI, dolphins don't.
The real question is: OK, so we have big brains, but why?
It could be - I'm just throwing up some ideas here - that as our ancestors left the forests (or the forests left them), they grew terrestrial, into hunters, into tool-users, that they evolved big brains to allow more versatile behaviours in a broader range of environments than sylvestran apes. Proto-humans coped with desert, savanna, forest, riparian and coastal environments, with a habitat range from tropics to temperate zones, with hunting and gathering and tracking and following herd migrations, with memorizing what was and wasn't good to eat in widely differing habitats, with being able to throw rocks accurately, shape stone tools, all that sort of thing. All long before language. Indeed, the fossil record is scant in such fine detail, but it could be we evolved language *long* before we evolved sentience and language itself selected for big brains.
( Read more... )
