Brain expansion (Evolution)

by dhw, Monday, July 27, 2020, 11:30 (1578 days ago) @ David Turell

DAVID: I always have an issue with your theory if brain expansion. Fully explained many times.

dhw: Then please humour me. The modern brain implements thought by means of complexification and small-scale enlargement. Why is it illogical to propose that earlier brains also implemented thought by complexification, but when the brain did not have the capacity to implement thought by complexification, it added new cells, thereby leading to large-scale enlargement?

DAVID: Entirely possible as a theory, but as you describe it forced by a new idea, I don't find it factually consistent with sapiens history.

Thank you. The part of sapiens history we know shows complexification and minor expansion as responses to new requirements. This can hardly be regarded as running contrary to the idea that the same processes may have taken place in earlier, pre-sapiens times. But then expansion was the main response to new requirements until the brain had reached its optimal size for the human anatomy, whereupon complexification became the major response.

On the subject of shrinkage, and why David’s God would have given us 150 cc more than we needed:

DAVID: Please read carefully what I express, as it makes perfect sense to me. The larger brain allowed us through the mechanism of plasticity to tailor it for our exact future uses. And we did it.

dhw: That is the bit I do not understand. I’m sorry if you think I’m being obtuse. Please explain how the excess 150 cc, which stuck around for approx. 270,000 years not being used, “tailored” (whatever that means) our brain for the time when we would think our new thoughts which still wouldn’t use the 150 cc. Once again: If it was never used, why did your God put it there in the first place?

DAVID: Tailoring as a dress suit analogy. Sightly oversized and cut to to fit your body. The extra neuron webs were used in the plasticity mechanism, some remained as part of the newly deigned brain fitted to our uses and others abandoned as superfluous as we learned to fully use our brain which took time as we know.

What do you mean by the extra webs were “used” in the plasticity mechanism. Plasticity is simply the quality that allows for change. Thanks to plasticity, the brain is able to complexify and to expand.So what were the redundant cells "used" for if there were no new thoughts? Neither this nor the rest of your answer tells us why your God gave us extra, unnecessary neurons.

DAVID: What is your explanation? It happened. Mine makes pefect sense to me.

dhw: I do not believe that your God inserted the excess in the first place, although he may have designed the autonomous mechanism that led to the excess. And your “explanation” makes no sense to me, as argued above. My explanation is that whatever caused the expansion to sapiens dimensions did require all the cells. It was only when expansion became impractical, and sapiens began to think his new thoughts, that complexification had to take over from large-scale expansion, and – as we have agreed over and over again – complexification proved so efficient that some of the previously necessary cells became redundant.

DAVID: Well, we are still apart. The sapiens brain was oversized for 270,000+/- years, and although you admit the extra cells were there you cannot give a reason for them, as I have. Further expansion was not impractical, but obviously a bigger brain was never necessary.

I have just given you a reason. They were needed and used for the implementation of whatever requirements caused the expansion to sapiens-size. Only after a long period of stasis (270,000 or so years), when new ideas created new requirements, did the efficiency of complexification make those cells redundant. And I don’t know why you think further expansion was not impractical. That means the brain and consequently the head could have gone on expanding indefinitely. Could your body have supported an elephant’s head?

DAVID: London cabbies have thickened areas as a result of our God-given brain mechanisms. How do you explain the oversize?? You haven't ever tried!!! I do all the possible explanations and you never try any, only criticize. What is your thought about it?

dhw: It is not “oversize”! It is the size required and then reached for the implementation of ideas. ALL such changes are the result of the brain RESPONDING to new requirements! Cabbies need to memorize routes, and the effort to implement this requirement by doing the abnormal amount of memorizing has resulted in certain areas of the brain acquiring more cells (whereas most requirements are met by complexification). That is the whole principle on which my theory is based, and which I have summarized in the section you did not comment on. What I criticize is your belief that the early brain had to expand BEFORE there were any new requirements (which according to you ought to mean that the cabbies' brain areas thickened BEFORE they could memorize all the routes).

DAVID: The sapiens history does not fit your theory in any way. I see no reason to accept it.

You asked me to explain the thickened areas of cabbies’ brains, which in fact provide a clear illustration of my theory. You have simply ignored the whole argument, including the findings of modern science concerning how the brain responds to new requirements.