Human evolution; savannah theory fading (Introduction)

by dhw, Tuesday, August 02, 2022, 11:38 (842 days ago) @ David Turell

Brain expansion

DAVID: Our brain came with excess neurons or shrinkage could not logically have occurred. That cells had to be used and then had to be thrown away makes no sense.

dhw: You keep ignoring my explanation, so all I can do is repeat it. Our brain came with more neurons than those of our predecessors. I propose that those neurons would have been added for a specific purpose, though we can only speculate on what that might have been. (Weirdly, you proposed the purpose was to give us free will, as if our earlier ancestors were all automatons.)

DAVID: We've discussed this in the past and I've said all previous brains were similar and all had free will.

DAVID (July 19th): We came with extra neurons in our brain so we could use our brain as we wished which gave us free will.

If the extra neurons gave us free will, then clearly you think our precursors could not have had free will, but I’m pleased to see that you are now disowning this theory.

DAVID: I doubt they shrunk as ours has. God added those extra neurons to allow us freedom of brain development as we learned to fully use it.

There would have been no reason for them to shrink. They would have expanded in order to meet new requirements. I have no idea what your second sentence means. Do you think the gradual increase in earlier brain sizes and accomplishments indicated that there was no “freedom of brain development”? In your next comment, you agree to my explanation of shrinkage, so why are you inserting this woolly explanation here?

dhw: However, as the brain was no longer capable of further expansion – probably because that would have involved major changes to the anatomy – complexification took over from expansion and proved so efficient that cells which had been essential in the past now became redundant. Hence shrinkage. You have accepted this explanation, but now you ignore it again.

DAVID: Your continual use of an anatomic theory dismisses the evidence from the Neanderthals whose skulls were bigger with no problem evident. We both agree about shrinkage.

I said “probably”, but do by all means let us know your own theory about why sapiens’ brain stopped expanding and complexification took over. Thank you for once again accepting my explanation of shrinkage. I trust that will mark the end of this particular discussion.

DAVID: As we civilized our brains had constant expansion of use. Our brain arrived with the complexification mechanism in place, to be used as required, as you agree.

dhw: Yes, that is precisely what I propose: our new uses were implemented through complexification and not through the addition of new cells. And complexification proved to be so efficient etc., as bolded above. What’s the problem?

DAVID: The problem is your interpretation of the original added neurons and how they became present. There is no known required mew complex usage that drove their appearance from a natural cause, considering the simplistic lifestyle of our immediate predecessors.

Nobody knows precisely what new usages caused new cells to be added to any of the brains from our earliest ancestors onwards. But in some cases they appear to have coincided with changes such as bipedalism, new artefacts, new lifestyles (hunters/gatherers)….It is not unreasonable to suppose that something new caused the sapiens expansion, as opposed to your God performing an operation on a group of sleeping Moroccans to prepare them for innovations that wouldn’t take place for a couple of thousand years.

Braincase size unchanged

QUOTES: "The physical transformation of the human cranium over the past 160,000 years was probably driven by alterations in the face resulting from diet and lifestyle changes, not from the evolution of the brain itself as previously thought, a study has found.”

"The cranium, or braincase, of early modern humans dating back 200,000 years isn’t much different in size from those today, but has a significantly different shape, suggesting that the brain has become rounder over time."

"The leading hypothesis is that changes in behaviour, such as the development of tools and art, caused the shape of the Homo sapiens brain to change and, in turn, the skull that protects it." (David’s bold)

DAVID: so, the brain shape changed, undoubtedly due to our new uses of it with complexification and shrinkage as a result. No evidence for dhw's weird anatomic theory that a larger skull could not be accommodated.

The article tells us that the size remained unchanged! How does that come to mean that a larger skull COULD have been accommodated?