Introducing the brain: why so big? Part two (Introduction)

by dhw, Thursday, July 18, 2024, 09:22 (126 days ago) @ David Turell

dhw: The sapiens brain expanded 300,000 years ago to meet new requirements, and for 290,000 years ALL the cells were devoted to the same purpose: survival. They may well have undergone a small degree of complexification during that time (we have no way of knowing), but 10,000 years ago, new requirements arose, and so the SAME cells complexified because expansion was no longer practicable.

DAVID: Thank you. All 300,000-year-old neurons were alive and at work at the level required then. Then at 10,000 years ago they all were available for all the new uses. You've made my point. (dhw's bold)

But your point is that when the brain arrived it was oversized. No it wasn’t. The new cells did not hang around for 290,000 years doing nothing! They would have been used for the purpose which triggered the expansion in the first place: survival.

DAVID: Scurry about, but the view of oversized on arrival is obvious. Oversized does not mean unused in a minor way initially. Now it does math, music singing, gymnastics, puzzles, etc.

Oversized would mean that the new cells were superfluous. How can they have been superfluous if they were all being used?

DAVID: Your quote is correct: "The early cells were able to meet all new demands" for all future years!!!

dhw: Thank you. That does not mean they were superfluous for 290,000 years!

DAVID: Of course they were.

A moment ago (bolded above), you agreed that they were alive and at work! But now you have the first sapiens brain expanding for no reason with cells that were of no use until 290,000 years later! Just hanging around waiting! Our brains are believed to have shrunk in more recent times because certain cells became superfluous through complexification. Don’t you think the same would have happened during the 290,000 years of superfluity? Even in your absurd theory, why the heck would your God have put them there 300,000 years ago if he knew they would not be needed until 10,000 years ago?

DAVID: I never said neurons then did nothing.

You have just said that “of course they were [superfluous]!

DAVID: But they didn't do the tasks I described above. But note, they were prepared for those tasks 300,000 years ago.

dhw: Now what are you saying? That 300,000 years ago, your God programmed the brain cells to respond to all current requirements AND to all those that would arise 290,000 years later? You have agreed several times that your God would not have intervened to direct every single complexification throughout the history of brain development. Now you’ve got him operating on a few earlier homos to put new cells in their brains, complete with a programme for every single innovation that will take place 290,000 years later. And you moan about Darwinian just-so stories!

DAVID: Not your just-so! Those cells were there to be complexified 10,000 years later. The brain can't complexify unless enough neurons are there to fill new requirements.

Correct. The cells were all there at the beginning, were used mainly for survival, but after 290,000 years were able to respond to new requirements by means of enhanced complexification instead of expansion. The new requirements triggered the new connections. The original arrival of the new cells was not triggered by requirements which would not occur for the next 290,000 years!

“De novo”

DAVID: Our very large and complex frontal lobes are a giant jump from ape brains.

dhw: That does not mean that our large and complex frontal lobes were created “de novo” by your God. Even in your theory, you have your God operating on existing brains.

DAVID: Yes, taking Lucy's brain and then enlarging and complexifying it in large steps.

dhw: Nothing “de novo”, then. Thank you for agreeing.

DAVID: Our frontal lobe with five layers of specialized pyramidal neurons has no predecessor. It is de novo.

dhw: It is not the frontal lobe that has no predecessor, but the new additions. If you wish to claim that every single “evolutionary novelty” (Shapiro) indicates your God starting over again; “afresh; anew; from the beginning” (definition of “de novo”), then so be it. Exit common descent. But don’t tell us that your God takes an existing brain and then enlarges and complexifies it.

DAVID: Of course He uses previous brains, not as highly complex as ours.

Complexifying existing brains is not “de novo”. Thank you.