Human evolution; savannah theory fading (Introduction)

by dhw, Wednesday, August 17, 2022, 11:23 (618 days ago) @ David Turell

Brain expansion

DAVID: A designer knows when His design is complete.

dhw: Which brings us back to the question why your all-powerful God designed umpteen varieties of hominins, homos and brains before finally producing the only one he actually wanted to design. But of course, only God knows why, and he couldn’t possibly have been experimenting, or getting new ideas as he went along, because such a theory entails human thought patterns, and he only has those human thought patterns of which you approve.

DAVID: I have presented to you the evidence that God prefers to evolve all of His creations. Must I repeat? He evolved the universe, Earth, life.

You don’t need to repeat your belief in evolution, which I share. The problem you yourself have found insoluble is why he chose to design sapiens in stages, although he was capable of designing species without precursors. You have acknowledged that you have no idea why. I have offered you two logical theories to explain why, but you reject them on the grounds which I have bolded above.

dhw: [...] how do you know his exact wishes, and how does this prove that he did NOT give cells the ability to multiplY?

DAVID: Cells do multiply. Why did you ask? And I have said we cannot know God's personal reasons.

dhw: You keep telling us that early brain cells could not have added to their number, and so God had to engineer their expansion (multiplication). Do you now accept that early brains might have had an autonomous mechanism for expansion as well as for complexification?

DAVID: Our brain's abilities reflect the past brains. I assume they worked as ours does, new neurons in hippocampus only.

I agree totally that our abilities reflect those of the past, i.e. that the cells could autonomously complexify (you agree) and multiply (as shown by the modern hippocampus), and we have agreed that otherwise, complexification took over from multiplication in the sapiens brain. You have no reason to assume that your God did not give both abilities to the brains of our predecessors.

Prehistoric brains and pelvises

DAVID: It turns out our birth canal is still tough to navigate.

dhw: Yes indeed, so why do you think our pre-historic ancestors had no trouble back in the days when baby skulls got bigger?

DAVID: I'm sure they faced the same obstetric problems we do.

dhw: Probably a darn sight worse. So what is all this about God arranging it “so new heads fit into new sized brains all at once”? [dhw: see below for the complete quote.]

DAVID: Old homo birth canals were just like ours under God's deigns.

My answer to what you called the “pelvic problem” was that the cell communities would have adjusted themselves to accommodate the new sized skull, but no doubt there would initially have been a lot of deaths during childbirth. You pooh-poohed this possibility because God would have arranged it “so new heads fit into new sized brains all at once without all those messy deaths you prescribe”? Do you now accept the possibility that there would have been a lot of deaths during childbirth as a result of the new sized skull?

Hemispherectomy

QUOTES: "Adults who had one half of their brain removed in childhood to treat seizures can still recognise faces and words at a reasonably high level, suggesting that the organ can reorganise itself after major childhood surgery.”
“The fact that above-chance and broadly comparable performance for face and word recognition can be achieved following childhood hemispherectomy attests to the remarkable adaptability of the juvenile brain,” says David Wilkinson at the University of Kent in the UK."

DAVID: Makes the point!!!

dhw: It certainly does. You could hardly have a clearer illustration of the way brain cells autonomously change themselves in order to meet new requirements. Or do you think your God pops in to perform additional operations after the surgeons have done their job?

DAVID: No, He gave the brain the abilities we see. No stepping in.

Thank you for confirming my proposal that if God exists, he would have given cells the autonomous ability to change themselves in order to meet new requirements.