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

by dhw, Thursday, March 13, 2025, 12:28 (1 day, 0 hours, 43 min. ago) @ David Turell

DAVID: I think God created us. No natural need for our big brain has ever been demonstrated.

dhw: Our big brain, which you now seem to accept as having evolved from earlier brains (as opposed to your God having performed one of his many operations on our sleeping ancestors), has clearly given us advantages in the great dog-eat-dog battle for survival, which you accept as an explanation of evolution’s history.

DAVID: A non-answer to the issue of what natural requirements caused our brain development?

dhw: We’ve been over this a hundred times. A tiny example: The hunter gets injured when trying to kill his prey from close up. New concept: maybe he can design a weapon to do the killing from a distance. The brain now has not only to work out the details of something entirely new, but also has to send new messages to the body to implement the new concept. In modern times, we know that implementing new concepts requires new complexification of the brain (illiterate women, taxi-drivers etc). The early brain’s capacity for complexification was limited, and so it required new cells – hence expansion. Multiply the scale of this example by the demands made by a new environment. Cause and effect all the way through until the brain (sapiens) could expand no further and complexification took over. Remember?

DAVID: You are totally ignoring the massive jump in size and complexity from chimp brains to ours as Lucy went on to develop hominins and finally humans. It has taken 300,000 years to begin to fully us our brains in the current civilization, which were vey over-complex and over-sized on arrival.

We have discussed this ad nauseam. After much huffing and puffing, you agreed (a) that the brain RESPONDS to new challenges (as opposed to anticipating them) and would always have complexified or expanded when the capacity for complexification was exceeded, and (b) that ALL of our expanded sapiens brain would have been used from the outset, not hanging around doing nothing for 300,000 years, and further developments were implemented through complexification and not expansion. I don’t know why you’ve raised this subject again, but we can use it as an example of how new conditions (e.g. savannah as opposed to forest) may lead to anatomical changes, including changes to the brain.

dhw: […] our subject here is the origin of sapiens: why is your divine surgery on groups of ancestors more likely in your eyes than a group of ancestors being forced from the trees, surviving in the savannah, and spreading far and wide into all sorts of environments?

DAVID: The new findings timing in history negate the savannah theory. There were lots of non-savannah folks living all at the same time.

The new findings show that they were living with sapiens. They could not have been living with sapiens if sapiens did not exist. And the question answered by the savannah theory is HOW sapiens came to exist – not what he did after he had come into existence.

Human evolution: Paranthropus robustus walked upright

A new fossil find in South Africa:
https://phys.org/news/2025-03-fossil-discovery-early-human-ancestor.html?utm_source=nwl...

DAVID: dhw worries about sapiens origin. All we can say is we evolved from one of the many ancestors we had. Homo ergaster, mentioned above, is considered to be a form of Erectus fossils so we can follow the line of development to some degree. Paranthropus robustus may not be in that line.

dhw: I’m not worried – just curious! I don’t think anyone who believes in evolution would deny that we evolved from our ancestors! But I must confess, I find the savannah theory a bit more convincing than your own theory that your God popped in and performed leg and hip (and brain) operations on a group of our ancestors - now expanded to several groups.

DAVID: As science in fossils advances with new findings, paradigms die. (Thomas Kuhn)

dhw: A possible answer to your brain and Cambrian paradigms, and for all we know, new fossils might support the savannah paradigm rather than your divine surgery paradigm.

DAVID: I doubt it.

Nothing is certain. Even you can’t explain why your God would go on designing life form after life form for 3.X billion years before designing “de novo” the only forms he wanted to design. Nor does it make sense that your all-powerful God should have “evolved” all kinds of hominins and homos, but then had to perform operations on particular groups to turn them into the only species he really wanted - sapiens with new legs, pelvises and brains.