Human evolution: savannah theory fading; big brain (Introduction)

by dhw, Monday, March 17, 2025, 11:23 (20 days ago) @ David Turell

The human brain

DAVID: My belief trumps your beliefs in the power of chance, purposeless evolution.

Nowhere have I expressed a belief in chance or in purposeless evolution. I have repeatedly rejected chance, and suggested that the brain expanded in response to new requirements, the purpose being to enhance chances of survival. The theory that the process is conducted by autonomously intelligent cell communities (possibly designed by your God) is an alternative to your all-powerful God performing operation after operation on lots of individual brains (not to mention legs and pelvises) in order to create the only species of homo he wants, although he’s perfectly capable of designing what he wants “de novo”.

DAVID: The savannah theory was a phantasy based on one finding.

dhw: […] It is generally agreed that we are descended from tree-dwellers. No one knows exactly where, when or why we first descended. The savannah theory offers a logical explanation for why. You will claim that your God’s surgery on a sleeping group (groups) is more logical.

DAVID: The savannah theory is no longer available as a single theory with the new findings of humans everywhere. Lucy shows us bipedalism came quite early.

What is a “single theory”? Humans are found everywhere because they migrated everywhere. “Quite early” leads us back earlier and earlier, until finally we come to the fact that we don’t know where, when or how the first sapiens came into existence. How does that invalidate the savannah theory, or validate your theory about God’s surgery on sleeping pre-sapiens?

DAVID: God guided brain enlargement and complexity as needed by the new environmental changes.

At least you now agree once more that complexity and enlargement occur IN RESPONSE to environmental changes, and not in anticipation. How does one “guide” enlargement and complexification? Did your God pop round to each pre-sapiens in the group with his X-Ray machine and scalpel, making sure the cells were arranging themselves in the right order?

Neanderthal sapiens mix in the Levant

DAVID: dhw's plea for origin places an emphasis on where did uprightness originate. Obviously in Africa before the great migrations into Europe and Asia. The levant was a major part of the route. The point of origin of bipedalism remains unknown. For those looking for a natural driving requirement living on savannahs is a reasonable but unsupported theory in view of all the new findings in other climates.

dhw: The new findings in other climates would relate to times when sapiens had already originated and migrated. I’m glad you recognize the logic behind the savannah theory.

DAVID: I follow Adler's theory that only a highly intelligent agent could produce humans.

dhw: The same argument can be used for the production of elephants, eagles and octopuses. I don’t recall you saying that Adler thought your God had operated on legs, pelvises and brains in order to produce sapiens.

DAVID: He just discussed the logic of God rather than naturally occurring evolution.

So please stop alluding to him as if he supported all your wacky ideas.

Theoretical origin of life
QUOTE: "The first molecules necessary for life on Earth could have been created when tiny flickers of “microlightning” between drops of water sparked the necessary chemical reactions.”

DAVID: a novel way precursor chemicals might have appeared, but it still is giant steps to life itself. I still favor ocean vents as the likeliest origin spots.

dhw: I agree completely that both theories are still a long way from providing us with the fine-tuning necessary for the appearance of life itself.

DAVID: Yes.

And those “giant steps” are what you have dismissed as “secondary” in your efforts to prove that the entire universe is fine-tuned for life even without them.

Origin of language
You seem to have agreed with my critique of this article, apart from the final paragraph:

DAVID: our brain seems prepared in advance to produce words and syntax. Early on there were grunts and gestures and common grunted sounds became words. The logic of the article using migration times is irrefutable.

dhw: You are always desperate to have the brain prepared in advance, although you acknowledge that brain development occurs IN RESPONSE to requirements, and not in anticipation of them. I would suggest that all the necessary anatomical changes came about through need and usage, not through your God consulting his crystal ball and popping in to perform operations. And I would say that the logic of migration as the cause of DIFFERENT languages is irrefutable.

DAVID: I'll stick with my prepared in advance theory, our 315,000 year-old brain as proof.

You have agreed that our entire brain has been in use from the beginning, that the brain RESPONDS to new requirements, and in our case it does so through complexification, which you agree takes place without your God’s intervention. Our disagreement is that you insist your God performed brain surgery on a sleeping group or groups in order to enlarge their brains, whereas I propose that our brains expanded in response to new requirements, and complexified thereafter, again through responses. This still allows for your God as the inventor of the mechanism that runs the process.