Evolution and humans: big brain size or use (Evolution)

by dhw, Tuesday, May 30, 2017, 20:12 (922 days ago) @ David Turell

dhw: The intimate work consists in the plastic brain responding to the requirements of consciousness: since that is what is demonstrated by the study, it makes perfect sense that it would also apply to the enlargement of the brain until it reached its optimum size. I presume your thanks denote agreement, so why have you spent the first part of this post disagreeing?
DAVID: Because what I conclude from the studies is opposite from you conclusions, which do not explain the small shrinkage in our brain size in the past 50,000 years.

You have now totally ignored all the previous arguments (repeated below) and are suddenly telling us that the current shrinking brain proves that the enlarged brain must have preceded the enhancement of consciousness. Why? It simply suggests that increased density is now more important than size.

DAVID: I think it should be clear that when a 200cc increase in size is mentioned, what that means should be visualized. The increase is roughly equivalent to a seven ounce glass of water. That is a big jump in brain volume. It doesn't reveal if complexity or density are increased in the newly enlarged brain, but its evolution involves coordination with skull growth to accommodate the new volume. Not a simple process.

Since nobody has yet come up with an explanation of how saltations (big jumps) work, I would have said the process must be extremely complex.

Comment: H. erectus had a brain size of 900cc, and is showing development of an advancing human use of the brain at 1.8 million years ago. But Lucy is 3 million years ago at 400cc and the Oldowan tools did not require much brain activity at 2.8 million years ago and were made by H. habilis, who preceded H. erectus. Habilis brain size was 640cc. The brain was simply used until recently, and intensely in the past 10,000 years, but is slightly smaller. Based on the adolescent brain study quoted earlier, I would guess our brain is becoming more dense. Size first use second.

I would also guess that our brain is becoming more dense. Clearly, therefore, size is not the causative factor in the advances of consciousness. If I were a dualist and an afterlifer, I would say that since consciousness/the self is separate from and survives the brain, which is only a receiver, and since consciousness uses and actually changes the brain, it is clear that consciousness provides the concepts, and the brain responds by changing itself – in the early days by way of enlargement, but later by way of densifying. And thanks to the brain’s plasticity, densifying makes size even less important – hence the slight shrinkage. And if I were a dualist, I would oppose any view that made the evolution of consciousness dependent on the growth of the brain. As a dualist, you have agreed with all of this. And yet suddenly, for no clear reason, you think a bit of shrinkage invalidates it all.


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