Introducing the brain: half a brain is just fine (Introduction)

by dhw, Saturday, February 22, 2020, 11:07 (1734 days ago) @ David Turell

dhw: Whatever may be the source of ideas, it remains a fact that nobody has ever seen a brain complexify or expand in anticipation of new ideas. All changes we know of take place as a response to new ideas.

[dhw] DAVID: (This is you speaking, not me!): The bold is a statement as if fact.

Then please give me a known example of brains complexifying or expanding in anticipation of new ideas.

DAVID: All we can know from the past is brains enlarged and then new processes and new concepts appeared. Erectus never had concepts habilis exhibited or then H. sapiens developed. Larger brains required for the conceptual advances.

You have no way of knowing whether the enlargement preceded the concept (larger brain thought of and implemented spear) or was caused by it (small brain thought of spear, needed larger brain to make it). However, once the larger brain was there, then of course there would have been more new concepts and implementations, until once again the capacity was exceeded by new concepts requiring greater capacity. The only clue we have for the sequence is the manner in which the modern brain functions, and that is brain changes in response to concept.

DAVID: You may explain but I don't accept your theory.

Fair enough. But you have yet to give me any logical reason for rejecting it.

DAVID: We have the example that refutes you. Our current brain with all its new uses and demands for even more new uses shrunk 140 cc from 30,000 years ago.

dhw: In post after post after post I have explained that once complexification took over from enlargement (the body could not take more enlargement), it proved so efficient that the brain did not need so much capacity. I have even asked you for your own theory. (Did God pop in? “Sorry, guys, I gave you a bit too much.”) You have not replied.

DAVID: God gave us all the brain required with its plasticity/local complexification abilities.

I answered your point about shrinkage. Why won’t you tell us your own theory about it?

DAVID: Your 'new requirements' were what? When H. sapiens appeared 315,000 years ago what were the demanding new requirements that forced the brain to suddenly enlarge 200 cc?

dhw: I’m really sorry, but I wasn’t around 315,000 years ago and I wasn’t around at the time of the earlier expansions either. [...]

DAVID: An early erectus brain lacks the capacity, as you admit, so cannot know what a habilis can know or imagine. Your view presents us with a totally illogical theory. What pushes brain committees of neurons if they do not know what they do not know and cannot know? You theory still requires the push of foresight.

Habilis preceded erectus. I don’t want to get into specifics, but of course later species would already know the concepts of their ancestors and would then add their own concepts, so the earlier species would not have known what the later species knew. Hardly a revelation. Your question about neurons rejects the possibility of any kind of innovation, assuming neurons are the inventors – which you as a dualist should reject! But even if you subscribed to the dualist belief that the soul is the source of ideas, you might as well ask how a soul can invent anything new. As regards “foresight”, same as usual (e.g. you think your God supplied pre-whales with flippers before they entered the water): My proposal is that the brain enlarged in response to new demands. Your proposal is that God enlarged it in anticipation of new demands (by personal dabbling or through a 3.8-billion-year-old computer programme for every non-human and human development you can think of).

DAVID: There are currently indigenous tribes now extant that live in roughly the same fashion as 315,000 years ago, with the same sized brain as the rest of us. […]

dhw: You keep asking me how I think the brain expanded. Now you want to know why, once it is in place, some people use it more than others! The pre-sapiens brain would have expanded because of requirements. Once it had reached its present size, all sapiens would have it. Some sapiens have more requirements than others and so use their brains more, presumably complexify more, and even undergo minor expansions, but their brains have also shrunk because of the efficiency of complexification. What do you think should happen? Do you want your God to pop in and shrink the indigenous tribes’ brains back to pre-sapiens’ size?

DAVID: Please understand the indigenous simply haven't bothered to use their big brain.

That’s what I’ve just told you.

DAVID: They just like it as it is. Note the illogical bold. The indigenous have not required the big brain so why did they get a big one? The Homo Hobbits had a small brain and lived as the indigenous until 30,000 years ago before disappearing. Why didn't they get the required big brain?

My point is that they DID get the required brain – though I don’t want to speculate on who turned into who. You have a succession of enlargements and a succession of species, each one caused by new requirements. The smaller brain disappears...stasis…THEN new requirements…enlarged brain…disappearance of smaller brain...on and on until the final enlargement with sapiens. The indigenous are sapiens. They’ve got the big brain but they don’t use it as much as you do. What’s the problem?

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