Evolution and humans: big brain size uses energy (Evolution)

by dhw, Thursday, October 26, 2017, 12:20 (1982 days ago) @ David Turell

DAVID: I know brains expanded in jumps with each new species in the advance of hominins to humans, and your approach does not fit the facts of brains becoming smaller among humans with increased use.

dhw: From the prioritization of brain mass you somehow extrapolated the claim that “the entire transition from trees to ground was a well-planned transition”. You then agreed that the brain did not change before pre-humans left the trees, which supports my argument that brain expansion was a RESPONSE to the new conditions and was not planned beforehand. As for brain shrinkage in Homo sapiens, we dealt with that in detail, my suggestion being that once the brain had reached a certain size, expansion was no longer an option and so complexification (rewiring) took its place, as exemplified by the illiterate Indian women, and this proved so successful that the brain no longer required its original mass. Do we really need to go over all that again?

DAVID: I'll again ask, shouldn't you note that my scenario fits the facts as much as you think yours does? Also most of our giant pre-frontal cortex arrived long before we figured out how to be civilized and develop all the non-material concepts now present in the arts and sciences. It is still obviously size first use second.

“God did it” certainly fits the facts, just as “diet or climate change or upright posture or random mutations did it” fits the facts. The only fact is that the brain expanded and is now shrinking, and nobody knows why, so you can offer any explanation you like. However, if the giant cortex was already present, the non-material concepts now present in the arts and sciences would have coincided with the process of brain complexification (rewiring and shrinkage), since the brain had reached its optimal size. We do know from the case of the illiterate Indian women that new concepts in this modern age result in rewiring. This clearly indicates that new concepts precede material changes to the brain, which runs contrary to the theory that material changes to the brain give rise to new concepts. We have been over all this again and again. The second point we have been over again and again is that your insistence on size before use (during the times before complexification took over), with its implication that the brain is the SOURCE of new concepts, runs counter to your dualistic belief that the brain is only a RECEIVER of ideas thought up by the “soul”. I’d better repeat that I am not taking sides in the dualism versus materialism debate, and I did try to reconcile the two hypotheses but can’t find the post. I shall eventually try again.

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