Introducing the brain: half a brain is just fine (Introduction)

by dhw, Thursday, March 12, 2020, 07:56 (1715 days ago) @ David Turell

DAVID: The first assumption has to be that our brain has processes developed from past brains and uses them in more complex ways.

dhw: Yes indeed, and since our modern brain follows processes of complexification and expansion (though now only on a minor scale) in response to – but not in anticipation of – new concepts, desires, plans etc., it is perfectly logical to assume that past brains did the same.

DAVID: Except for your 'in anticipation', we agree.

That is the nub of our disagreement, in the context of both brain and evolution in general. You insist that your God preprogrammed or dabbled all the major adaptations and innovations before they were required. I propose that they came about in response to new conditions.

DAVID: Your theory that the brain stopped enlarging because of anatomic size considerations is simply a wild guess, lacking any evidence for the point.

dhw: If the brain had continued to expand, we would have had elephantine heads! Expansion had to stop somewhere! That is not a wild guess – it is a logical assumption. What is your explanation for the end of expansion and the takeover by complexification?

DAVID: I gave you the conversion of cc to ounces. The biggest enlargements were less than seven ounces. 'Elephantine' is pure silliness. We got to this final point in small steps. It is all we need and it shrank from increased uses.

If expansion had gone on indefinitely, we would have finished up with elephantine brains, no matter how many ounces or ccs each expansion was! One moment you’re telling us how big each expansion was, and the next you’re telling us these were small steps. It makes no difference, and it also makes no sense to say that it shrank from increased uses when we know that in the case of taxi-drivers and musicians, some sections expand through increased usage. It shrank over all because complexification took over from expansion (you pooh-pooh the logical reason I have proposed, but can offer none of your own), and complexification was so efficient that some of the capacity was no longer needed. (dhw's bold)

dhw: Yes, both complexification and enlargement come from usage, not in anticipation of usage.

DAVID: The bold is so obviously backward in its misuse of the facts. Sapiens arrived with a barely used brain and then employed your implementation process with in the end shrinking.

You have totally missed the point of our whole discussion, which concerns the reason for each expansion. That is why I keep emphasizing that it is the first artefact that would have been the cause. Once the new brain is in place, it continues to produce new things until the next “big idea” requires further capacity. Each new capacity is “barely used” initially, and then it is used until it proves inadequate. Sapiens’ capacity would have arrived in the same way, but when new concepts had to be implemented, it complexified instead of expanding etc., as above.

DAVID: And I say this last brain was given the capacities to not need any further expansion.

“Was given” or “has” makes no difference to the process – it stopped expanding and complexification took over. You have no idea why your God would have made it bigger than necessary - “Pounding same dead horse. I don't look for His reasons. No need.” – whereas I have provided a logical explanation for the whole sequence.

dhw: But you think your God made our brains larger than necessary and preprogrammed or dabbled shrinkage, and you have no idea why.

DAVID: Nor do you.

No, I can’t see any logic behind your theory, which is why I see no reason to believe it. I offer a perfectly logical alternative.

dhw: Please note that in my theory it was a new "heavy use" that caused the brain to expand - just as it does today, though on a lesser scale.

DAVID: Silliness again. Our overall brain shrank. Don't try to hide a major point.

I don’t know how often you want me to repeat the explanation. Please reread the bold above. Plus the paragraph beginning "You have totally missed the point..." which you continue to do.

DAVID: All we have is fossils, with differing brain sizes, and artifacts that advance as size increases. Archaeologists simply observe this and assume the larger size allowed the advances. [dhw: Please for the second time reread the paragraph beginning "You have totally missed the point..."] I don't know why God allowed a bigger brain before it shrunk. Do you? But those are the facts we have, and you can't understand His logic either. Your obvious point is if God did something illogical, He doesn't exist.

This is the silliest argument yet! I do not accept your theory that your God preprogrammed or dabbled each expansion before it was needed, plus the shrinkage which you can’t explain! It is your illogicality that I don’t understand, not God’s! If God exists, I have proposed that he provided the mechanisms that performed all these actions as intelligent cell communities responded to changing conditions. And my “point” here is that I do not for one second believe that God would do anything illogical. That is why your whole theory falls apart, and I offer you various theistic alternatives in which your God’s actions are totally logical.

See “David’s theory…” for the last part of your post.