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

by dhw, Saturday, July 13, 2024, 09:02 (57 days ago) @ David Turell

Evolution of the brain

dhw: So although the planarian is the first animal to possess a brain and may be the ancestor of the vertebrate brain, you know that it did not have a brain and cannot be the ancestor of the vertebrate brain. I get it. Is this your Jekyll or your Hyde speaking?

DAVID: I said it is a degree of complexity of the original neurons and brain complexity. The jump to Trilobite brain is an enormous gap, isn't it?

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?

Why is our brain so big?

DAVID: […] Our brain is much too big and complicated for the single purpose of survival. […] In short, human beings cannot be explained by Darwin's theory of evolution.

dhw: Of course our brain has evolved beyond the single purpose of survival! […] The question [Darwin] tackles is how species originate. […]

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: 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: Pure Darwin just-so speak.

Your just-so speak, if I remember rightly, is that your God operated on some tree-dwellers to change their anatomies, and told them to go walkies. Please tell us what’s wrong with the logic of the theory described above.

DAVID: Let's look at 'de novo'. Do you remember the story I presented in which the scientists had carefully dissected a small area of our brain and found how amazingly complex it was. Jumping from Erectus to sapiens brain is a major de novo design change.

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”(See below.)

DAVID: A better explanation than advance by chance!

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.

The brain: why so big?

QUOTE: “Evolution doesn’t just invent new brain structures and suddenly you can speak or whatever. It’s the other way round. You start speaking and then this creates a new cultural environment under which there are new selective pressures that favour new brain structures.”

dhw: The other way round means that speaking is what changes brain structures, and we know for a fact that new activities cause such changes (the illiterate Indian women, the London taxi-drivers etc.). The author has omitted this crucial stage. But new abilities also engender new requirements – hence the continued increase in size, even within the same species (H. erectus), until size becomes limited and complexification takes over. Nothing “de novo”. Each brain adds to or complexifies existing brains.

DAVID: Plasticity do not introduce new brain structures or complexity, only more of the same.

Who says the brain can only reproduce “more of the same”? 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?

DAVID: [...] The size discussion ignores the complexity issue…

Spot on!

DAVID: ...in which a smaller brain can be more highly complex and produce unexpectedly advanced products (artifacts).

dhw: I would suggest that the artefacts produced by our ancestors were at least partly the cause of expansion: the smaller brain conceived the idea, but the implementation of the idea caused the expansion. New requirements produce changes. As above, these changes may produce more new requirements and so the process continues.

DAVID: Again, you favor chance improvement over designed.

No chance involved if cells have the intelligence to do their own designing.

DAVID: Throughout the article no explanation appears that ever answers the question: 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.

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.