Human evolution; savannah theory fading (Introduction)

by dhw, Thursday, August 18, 2022, 13:15 (616 days ago) @ David Turell

Brain expansion

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

dhw: 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.

DAVID: You can assume that possibility as pure unsubstantiated theory.

Nobody knows the truth, which is why we have different theories. However, since the hippocampus apparently has the autonomous ability to enlarge itself, we have evidence of brain cells being able to add autonomously to their numbers, and so the possibility that they were able to do so generally in the past is not entirely unsubstantiated. We also know that for unknown reasons expansion was made unnecessary by means of enhanced complexification, and so - sticking to theism – one might say that your God’s creation of such an autonomous expansion mechanism is at least as feasible as the theory that he kept on performing operations on sleeping hominins and homos in order to give them their new cells.

Prehistoric brains and pelvises

dhw: Death in childbirth wasn’t all that uncommon in historic times, so it’s perfectly conceivable that such a problem would have caused more deaths in prehistoric times.

DAVID: You are very uncaring for our ancestors.[…]

dhw: […] why do you think our prehistoric 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: 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?

DAVID: My kind God provides for all required changes as He designs for future use.

But do you now accept the possibility that there would have been a lot of deaths in childbirth, as I proposed above?

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.

dhw: 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.

DAVID: All He gave the neurons is the ability to arrange new networks of connections in complexification.

That is all they need now, since expansion has ceased and complexification has taken over. But I’m happy with your conclusion, as you agree that brain cells are capable of changing themselves autonomously in order to meet new requirements. If brain cells can do this in the present, and we know for a fact that other cells can also make the minor changes necessary for adaptation, there is no reason to assume that other cell communities did not have the same autonomous capabilities in the past, when full speciation took place (as opposed to varieties, which we also call species). The current period of evolutionary stasis is very short compared to those of the past, and who knows what new species might be formed by the same autonomous mechanisms if (when?) our planet – or parts of it - undergoes radical changes? It is pleasing to see you gradually coming round to the fact that your God could and did give a degree of autonomous, creative intelligence to cell communities.