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

by dhw, Sunday, March 16, 2025, 09:17 (18 days ago) @ David Turell

The human brain

DAVID: You want natural evolution. I have God the designer.

dhw: You wrote that “no natural need for our big brain has ever been demonstrated.” I explained that the “natural need” arose from new inventions, discoveries and conditions which required a greater capacity for complexification than was available at each stage of the brain’s evolution. I don’t “want” anything. I offer you a logical explanation, which you agreed to years ago, and now you pretend it’s wishful thinking. Please explain why you reject it.

DAVID: We departed from the primate line six million years ago. Apes and monkeys are unchanged. We went on to full bipedalism, intricate hand usages, bigger more complex brains etc. Did we push ourselves or was an agent doing it? I still favor God, the designer.

You have completely ignored my response above, and simply repeated your belief, which is that your God did it by popping in to operate on the brains of a group or groups of sleeping homos.

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

dhw: Thank you for agreeing that it is logical. The known new facts only tell us about migration out of Africa – nothing to do with the ORIGIN of sapiens. Now please tell us what new findings support your theory of God performing his various operations.

DAVID: No!! The article describes various non-savannah African habitats for the earliest developing proto-humans, in the same time-frame as the savannah theory.

What is the time frame for the unknown origin of sapiens? 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.

Earliest humans in Europe
At 1.2 million years ago:

DAVID: this puts us out of Africa at a very early time compared to other evidence.

dhw: The movement to different environments would certainly explain different traits between members of our own species. But of course it doesn’t tell us anything about the origin of our species.

DAVID: Lucy-forms from unknown forces or God at work.

dhw: “God at work” is an equally unknown force. Why bother with Lucy if all he wanted was to design you and me?

DAVID: Same request for direct creation, as shown in the Cambrian Explosion.

It’s not a “request”. You yourself can’t explain why an all-powerful God, capable of “de novo” creation, should have chosen to create the only species he wanted to create by having to create 99% of creations he didn’t want to create!

Neanderthal sapiens mix in the Levant

QUOTE: "The finding reveals that Neanderthals, modern humans and related human lineages coexisted in what is now Israel for about 50,000 years. However, it's unknown which group influenced the other and in what direction.”

dhw: The mystery deepens. We know that sapiens and Neanderthals interbred, and presumably this other unknown group did the same. Obviously they co-existed peacefully. And their shared cultures suggest sophisticated communication. The Neanderthal brain was at least as big as ours, so the big brain of sapiens is/was not unique. I wonder what was the brain size of the third homo.

DAVID: Brain size is a minor issue compared to neuron organization and complexification.

My answer at the start of this post was to your statement that “no natural need for our big brain has ever been demonstrated”. Neutron organization and complexification would have been the same in all the earlier brains, but they had to expand when requirements exceeded the capacity for reorganization and complexification, as explained above and formerly agreed by you.

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.

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.

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.

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.