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

by dhw, Wednesday, October 25, 2017, 13:08 (2370 days ago) @ David Turell

DAVID: A study on Lucy decided she probably was a partial tree dweller who fell to her death, but it was her slight build that originally hid that conclusion from earlier studies. Earlier hominins had smaller upper bodies than apes, while their brains were still small implying they left tree dwelling and then grew larger brains in that sequence.

dhw: If I’ve understood you correctly, then, the sequence supports my hypothesis that once they left the trees, there were new tasks to be performed, as a result of which their brains expanded.

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.

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?

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