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

by dhw, Monday, June 05, 2017, 13:17 (2726 days ago) @ David Turell

DAVID: Whatever is your previously learned philosophic interpretation of dualism is getting in the way of understanding my concept, based on the brain as a receiver of a mechanism called consciousness, which none of us understand what it is or how it works, but we work with it constantly. It doesn't forcefully run my thoughts, I do.
dhw: Once again, you, your self, your mind, your consciousness, your thoughts are all one, according to your belief in an afterlife in which you, your self, your consciousness and your thoughts exist but your brain doesn’t. Yes, the brain is the receiver not the generator of thought. It has been demonstrated that thought changes the structure of the brain (densifying) and not the other way round. It therefore seems logical that the same process would apply to size – that thought led to size and size did not lead to thought.
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.

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.

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

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.

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

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. If this is technically incorrect, then I’ll use the latter term. 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?