Evolution and humans: big brain size or use (Evolution)

by David Turell @, Monday, June 05, 2017, 15:10 (864 days ago) @ dhw

DAVID: Thoughts did not cause a giant jump in size of 200cc to reach H. sapiens. Not that much thought was required at that time. Simple language and an athletic hunting lifestyle was not that complex. You are again hypothesizing an internal drive that makes no sense. We have no known proof of how speciation works except the historical record. I prefer an external drive, God.

dhw: I don’t know why you keep talking about internal and external drives when you know full well that my hypothesis allows for your God. You continue to ignore your own avowed belief that consciousness and the self can exist independently of the brain, which is only a receiver. If you truly believe this, I simply cannot understand how you can also believe that consciousness and the self are incapable of increased conceptualization until the receiver brain increases its size.

My thoughts come from the fact that chimps are conscious with their 400cc brain, but do not show evidence of consciousness. Consciousness appeared as brain size grew, and more complex use of the brain (based on demonstrated activities of daily living) appeared with each jump in brain size. In H sapiens full use appears to have taken place over 200,000 years, and caused the brain size to densify and shrink a little.


DAVID: The problem with your scenario is that jumps obviously preceded use. Each level of hominin lifestyle was more complex, after each jump.

dhw: That is the issue. If consciousness is the generator of concepts, each level of lifestyle would be a new concept, and for that new concept to become reality, it would require a change in the brain (initially size, and later densification). The concept would precede the implementation, just as reading and writing are the concept, and the implementation causes a change in the brain. Concept (of new lifestyle) first, brain change and implementation second.

You have it all backward as explained in my comment above.


dhw: May I now ask how you know that densification only began 20,000 years ago? If this is true and, to take one extremely important example, if human language really did emerge 50,000 years ago along with changes to the vocal tracts, I find it quite astonishing that there was no densifying or restructuring of the brain at that time. How has this been established?

DAVID: You didn't see this entry: Saturday, June 03, 2017, 02:21 :
http://discovermagazine.com/2010/sep/25-modern-humans-smart-why-brain-shrinking

dhw: I did see it, and it doesn’t answer my question. I understand perfectly well how science can measure the SIZE of the brain, but that doesn’t mean that there were no changes within the brain before it started shrinking. Perhaps this is a problem of semantics, though. I do not see densification as shrinkage but as complexification.

Of course density is result of complexification. Quite correct.

dhw: For example, the concept of killing prey with a throwable shaft that has a sharp tip would require a new use of brain and hands and various muscles in order to manufacture and use the shaft. Perhaps this would require an expansion of the brain (a leap), or alternatively there could be new wiring among existing cells (= densification/complexification), without expansion. It is this second scenario that I am asking about here – generally, not just in relation to tools: how can we know that once the brain had reached its homo sapiens size, there was no densification (complexification) during the 180,000 years that preceded shrinkage, e.g. during the evolution of language?

Of course there was a degree of complexification during the first 189,000 years of H sapiens, but a critical mass of complexity to cause densification only came 11,700 years ago. And since then the brain has been used in massive new ways. Civilization as we know it is less than 10,000 years old!


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