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

by dhw, Sunday, July 14, 2024, 12:15 (56 days ago) @ David Turell

Evolution of the brain

dhw: Yes, there are gaps to and from. But do you believe that your God invented the vertebrate brain “de novo”, or that the planarian brain may have been the ancestor of the vertebrate brain?

DAVID: Very distantly of course. No where near the current complexity.

Of course early ancestors are “distant” and nowhere near current complexity. Thank you for now acknowledging that the vertebrate brain was not designed “de novo”, i.e. without predecessors.

Why is our brain so big?

DAVID: […] You champion Darwin's 'survivability' as a driver of evolution. Explain how the sapiens brain improved that ability, especially since our close cousins, the apes do just fine without it. Then add all the skeletal issues that allow us to do what apes cannot. (dhw's bold. See conclusion to this thread.)

dhw: The theory is that SOME of our ancestors encountered conditions that threatened their survival, and so they changed their environment. And this new way of life required the physical changes that led to bipedalism and new uses of the brain. Other apes survived perfectly well in their original surroundings. What’s the problem?

DAVID: The problem is you dodged with a just-so story. Was our huge complex brain necessary for survival, when their close cousins didn't need it. All living in the same African environment.

Africa is a huge continent, and all that is required is one local environment (perhaps even more than one) which necessitated the move from trees to land.

DAVID: Lucy's bipedalism preceded brain growth, showing that she did not need a big brain.

Brain growth would only occur when the existing brain could not cope with new requirements. We have no idea what new requirements may have caused each stage of expansion, but no doubt new environments, new ideas (artefacts), new discoveries (fire) would all have played a part. All of these would have improved our ancestors’ chances of survival.

dhw: No one is denying the complexity. All phases in the brain’s evolution entail “jumps” as new conditions require new complexifications or additional cells. Complications and additions do not mean that each brain is designed “de novo”

DAVID: A better explanation than advance by chance!

dhw: No chance involved if cells have the intelligence to do their own designing
And:
dhw: You have agreed that new sapiens connections (complexification) are made autonomously. Why can’t your God have given the same autonomy to cells when earlier brains complexified or expanded?
And:
dhw: There is no chance involved if cells have the autonomous ability (perhaps God-given) to changes themselves in order to cope with or exploit new conditions.

DAVID (repeated reply): Back-peddling to God.

You look at the complexities and back-pedal to your God designing every single one individually. I look at the complexities and acknowledge the possibility that your God might have invented the process that produced the complexities. What’s wrong with that?

DAVID: Viewed as a natural event how do our brain get big? Adler's supernatural answer: God.

dhw: If God exists, I would propose that he created a mechanism whereby existing cells had the ability to produce additional cells (expansion) and additional connections (complexification) when needed. That would explain why the vast majority of our brain structures can be found in our fellow mammals – we simply added to these. Sapiens brain was not designed “de novo”.

DAVID: Our frontal lobe has no predecessor of size or complexity. And it fits no survival need.

dhw: All mammals have frontal lobes. Those of our ancestors would have functioned for survival. As sapiens’ activities expanded, the frontal lobe would also have expanded in order to respond to the new requirements. Expansion and enhanced complexity do not equal “de novo” creation.

DAVID: Sapiens activities expanded because they had big brains to use. Ours is 300,000 years old and when did we use it fully? In the past 10,000 years.

I don’t know how many times you want to repeat this discussion! The question is how our brains evolved. You have agreed over and over again that early sapiens used their big brains almost exclusively for survival (I say “almost”, because some of our ancestors are known to have produced art, decorations, rituals etc.) Your figures would be 290,000 years for survival. When the cultural “explosion” began, our big brains did not expand! They complexified. The original additional cells would not have simply hung around doing absolutely nothing for 290,000 years, but simply being passed on through thousands of generations! They were used for survival and then, according to you, for the last 10,000 years all new requirements have been met by complexification of existing cells, which has been so efficient that some of the existing cells were no longer needed (hence shrinkage). By insisting that the big brain was initially used only for survival, you have agreed that survivability was what drove the evolution of our brain, as per Darwin.