Human evolution; savannah theory fading (Introduction)

by David Turell @, Thursday, August 04, 2022, 19:09 (6 days ago) @ dhw

Brain expansion

dhw: I propose that our additional cells followed exactly the same pattern as before: all our ancestors had “freedom of development” – which resulted in the addition of cells when needed! But for reasons unknown, we reached a stage at which complexification took over from expansion and proved so efficient that some cells became redundant. You agree, so what’s the problem?

DAVID: That is not my position. Based on how our brain arrived with excess neurons, I'm convinced Habilis and Erectus had similar beginning excess capacities. Our brain must reflect the past forms.

dhw: This is new. There is no evidence that Habilis and erectus brains shrank – on the contrary, we know that erectus’s brain expanded, i.e. added new cells, presumably as and when there were new requirements.

There are not enough fossils to answer all question, but brain shrinkage is accumpianed without skull case shrinkage.

dhw: Until now, you have focused entirely on the astonishing jump in sapiens’ thought capabilities and “excess” cells (which I propose were not excess at all, but were necessary at the time), as in your next question:

DAVID: What new single event required such a jump in brain thought ability?

dhw: You are asking me to solve mysteries which nobody else has solved. But I have given you examples of past events that might well have required additional cells, and so it is not unreasonable to suppose that the same process would have repeated itself.

DAVID: So you assume the needed extra cells in new species simply appeared magically? New designs require a designer.

dhw: There is no magic if you accept the theory of cellular intelligence (possibly designed by your God)! At every stage, when complexification could no longer cope, new conditions/discoveries/inventions/tools/lifestyles required additional cells for their implementation. But for some unknown reason, sapiens’ brain generally stopped expanding, and complexification took over, with such efficiency that cells which had previously been necessary then became redundant. You keep agreeing with this last explanation, so I don’t know why you keep faffing around with new objections.

I agree with your description of events but reject your intelligent cell theory.


Braincase size unchanged
QUOTES: "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.

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

DAVID: The Neanderthal's accommodated a larger brain and skull. That destroys your accommodation theory.

dhw: You tried to use the article as proof that a larger size could be accommodated, but it shows clearly that it was the shape and not the size that changed. Neanderthals were a different build from us, and their brain size was not massively greater than ours, and may even have been the same size as those of their contemporary sapiens. But again, you are asking me to solve problems that nobody else has solved. And you have not yet given us your own theory as to why our brain stopped expanding and reverted to enhanced complexification instead. Please tell us.

DAVID: I have told you previously: God designed our brain as an endpoint in evolution. It came with all the capacity it would ever need. Its conceptualizing ability seems endless based on present evidence of ideations. It came oversized to allow us to mold it as we willed. It came with a complexification mechanism to accommodate our free use of it.

dhw:n You are talking as if your God designed our brain from scratch! It evolved from all the earlier brains and it reached a point at which it stopped expanding. You have agreed that all previous brains would have had a complexification mechanism, but at all stages except ours, this proved inadequate for new requirements and so they produced additional cells. I propose that no brain, including our own, was “oversized”, and why on earth do you think that the cells of erectus’s brain could not complexify as they “willed”. Was erectus a robot? Did habilis not have “free use” of his brain?

God does design from scratch when first brains appeared and designed all future modifications. I've said previously erectus and habilis had free ill. You've invented my mind as changing.


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