Brain complexity: learning new tasks (Introduction)

by dhw, Wednesday, December 06, 2017, 13:21 (8 days ago) @ David Turell

DAVID: You seem to be accepting that the current human brain is an end point, which fits with my belief that it was/is God's purpose to produce.

You wrote “Nor am I sure that further expansion is not possible…” and I agreed with you, but even if it can’t expand any more (earlier you dismissed the idea of huge brains as sci-fi), I do not agree that your God would have geared the whole of evolution to the production of our brain, which is your idea of his “purpose”. An “end point” is simply the final stage of a process. If the human brain is an end point, so are the duckbilled platypus, the skull-shrinking shrew and the whale.

DAVID: You do not seem to understand my theory, A small brain is limited in the concepts it can develop. Pre-habilis could not understand the concept of spear. It took a habilis-sized brain to have the concept and implement it, both occurring in the same brain, not a subsequent larger addition.

I do not understand a theory that contradicts itself. Let’s forget pre-habilis, since you begin with habilis: “If habilis has an idea for spears, the idea is immaterial. No brain change.” So small-brained habilis has the idea. “Once he learns to knapp flint, attach the stone point to a wooden rod, and then practices throwing it with accuracy, there is no question that the brain has enlarged with all the muscle movement and visual coordination involved.” It is therefore the implementation that enlarges the brain, and so from then on we have a post-habilis with a larger brain. (You went on: “But then the brain complexified and shrank” – skipping to Homo sapiens and the Indian readers, when the brain had stopped enlarging.) According to you and to me, the concept comes first, the implementation then enlarges the brain until we reach sapiens. You have described the process perfectly.

dhw: The skull does not change in Homo sapiens! But it expanded in pre-sapiens! If the brain expanded beyond a certain limit, the skull had to expand to accommodate it until it reached a point (sapiens) when it stopped expanding, and complexification took over.

DAVID: You accept that pre-sapiens brains might complexify with new implementations and then you withdraw the idea! And sapiens did have brain and skull shrinkage as part of the known history.

I have not withdrawn the idea! I don’t believe that EVERY new concept and implementation resulted in a new species of hominin! The pre-sapiens brain would have complexified in each form of hominin until complexification proved inadequate to implement new concepts, and then it expanded exactly as you have described above. Sapiens could not expand any more, and so complexification alone had to cope, and did it so efficiently that the brain has shrunk.

dhw: We remain in perfect agreement, except that you refuse to agree that we agree.

DAVID: We have never agreed on my point that more complex concepts require a more complex larger brain to be developed and then implemented. Size first, use second. Artifacts fully support my idea. I find yours totally illogical.

Again you use “developed” ambiguously. The smaller brain has the concept (as you have described), and the brain enlarges as it implements the concept (as you have described). Concept first, implementation second, new size results from use, which is part of implementation (as you have described). The concept may be still further “developed” in the new larger brain, but in due course, once complexification is inadequate, implementation of the further developed concept will again require further expansion. Each new, further developed artefact can only appear when the brain has finished its latest stage of enlargement (as you have described). That is why you will only see the respective artefacts together with the fossils of the larger-brained hominin that implemented the concept. I’m sorry that you find your perfect description of the process “totally illogical”.

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