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

by David Turell , Wednesday, May 31, 2017, 01:37 (2732 days ago) @ dhw

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.

dhw: 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.

Increasing density is due to more complex use of a very responsive brain. Remember complex use started 10,000 years ago, with very simple use before then. The vast brain was there waiting for uses to appear. Now we see the new effect.

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.

dhw: 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.

I would agree to all of this in a way, except the consciousness/me/self are the same and so I produce the uses and concepts which modify a brain that is already large and can handle the conceptual processes as they appear.

dhw: 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.

Not at all. Shrinkage tells us the a highly used brain can become more dense and shrink and is simply a measure of the new usage. I've said in the past and again now, enlargement of the brain made it a better more competent receiver of consciousness. Size first, use second.