Brain expansion (Evolution)

by dhw, Tuesday, July 28, 2020, 16:53 (1577 days ago) @ David Turell

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.

DAVID: What happened to 'forced by a new idea'.

“Forced” is your word, not mine, but in any case my comment above is a response to your claim that my theory is inconsistent with sapiens history. I have shown you that it is not.

On the subject of why David’s God is supposed to have given sapiens 150 cc of brain cells that later disappeared:

DAVID: 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.

No it didn’t. What thickened their brain area was the effort to fulfil the requirement to memorize new routes. Plasticity is what ALLOWS the brain to change. It is not the cause of the change.

DAVID : 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.

“Carefully reconstituted”? Sapiens started off with a brain that contained 150 cc of cells that were never used again, and so when he started to implement his new ideas through enhanced complexification, the unnecessary cells disappeared. That doesn’t mean the entire brain was carefully taken apart and put together again in a different form, and it still doesn’t tell us why your God gave us more cells than we needed.

DAVID: 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: 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. […] Could your body have supported an elephant’s head?

DAVID: 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?

Once again: my theory is that ALL the enlargements were caused by new requirements that could only be met by additional cells. NOBODY knows what these requirements were! But all expansions, including our own, were followed by periods of stasis, when there were no new ideas that required any further changes! Modern science confirms that the brain changes in response to new requirements and not beforehand. So what theory have I abandoned?

DAVID: 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. [...]

The question here is why the sapiens skull stopped expanding. We weren’t in trouble with the extra 150 cc. because the skull expanded enough to accommodate it. According to you, your God stepped in, and next morning a group of homos woke up with a bigger brain, skull AND pelvis. So why didn’t he just go on expanding brains and skulls and pelvises indefinitely? Maybe he wasn’t too keen on expanding sapiens’ heads to the size of elephants’ heads and having to keep dabbling with pelvises?

DAVID:London cabbies have thickened areas as a result of our God-given brain mechanisms. How do you explain the oversize??

dhw: It is not “oversize”! […] Cabbies need to memorize routes, and the effort to implement this requirement […] 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 […]

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 (bolded above), 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.

DAVID: I ignore nothing. i wan't asking you about cabbies.

Read your own now bolded question.

DAVID: [...] I confused you. I was asking for your theory about overall expansion, because your original theory seems to have disappeared.

My original theory remains exactly the same as it was, and your question about the cabbies serves only to confirm that both complexification and expansion are the RESULT of the brain meeting new requirements. Again: which part of my theory has disappeared?