Brain expansion (Evolution)

by David Turell , Tuesday, July 28, 2020, 00:39 (1578 days ago) @ dhw
edited by David Turell, Tuesday, July 28, 2020, 01:03

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.

dhw: 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.

What happened to 'forced by a new idea'.

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.

dhw: 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.

Plasticity reshapes webs for more efficient use. It uses whatever exists and extra neurons allow slight enlargement of specific regions. It thickened the London cabbies brain area. We see both much shrinkage and slight growth, but overall the extra cells were discarded after the brain was carefully reconstituted as specialized networks to fit the uses humans found for it, with final overall shrinkage.

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.

dhw: 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?

Still no answer describing the new idea that drove the enlargement, but then no application for 270,000/+ years. We know of none! Enlargement and then stasis during sapiens appearance on Earth does not fit your favorite theory of ideas forcing enlargement. Is it abandoned?
As for head size, previous hominins size jumps of 200 ccs bothered no one. and we were not in trouble with 150 cc extra. 'Elephant head' is one of your weirdest worries. Considering the sharpness of our brain, never needed. Never would have happened.

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.

dhw: 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.

I ignore nothing. i wan't asking you about cabbies. We both know the reasons. I confused you. I was asking for your theory about overall expansion, because your original theory seems to have disappeared.