Big brain evolution: comparing chimp and brain organoids (Evolution)

by dhw, Sunday, February 10, 2019, 10:32 (195 days ago) @ David Turell

Dhw: I’m very happy with your expression “cooperative beneficial new genes”. This seems to me to sum up how the whole process works. I would suggest that the big leap from a handful to several hundred would coincide with the different stages in between our ape ancestors and H. sapiens. The brain expanded (= new cells/new genes), as existing cells cooperated to enable hominins to cope with changing conditions or to implement new ideas that required new skills.Today, as we noted in our very long discussions on this subject, the brain complexifies – and indeed that process has proved so efficient that there has even been a shrinkage.

DAVID: Humans have five layers of neurons in the prefrontal cortex not at all present in chimps, in a highly complex wiring set of patterns that AI folks are trying to imitate. One must assume from the jumps in fossil cranial size these layers also appeared in jumps in complexity requiring design that a committee of neurons could not envision before they were wired properly. Each wire/axon grows out from the central body of the neuron and at a distance makes multiple connection branches to other neurons. Unless guided what one would get is a pile of spaghetti. Your fanciful cell committees are out of their league. Designer required.

You are of course entitled to your belief that your God had to keep dabbling with pre-human brains in advance, to prepare them for new demands and uses, but there is less evidence for that hypothesis than there is for mine: we know that the modern brain rewires itself in accordance with new demands (the illiterate women), and despite the overall shrinkage some sections even expand according to use (taxi drivers, musicians). In both cases, the brain responds to new demands and to usage, and does not change in anticipation of them. NB: this hypothesis does not preclude design. However, if materialism is correct, then the brain is the source of new ideas – hence our lengthy discussions on dualism versus materialism, and the THEORY OF INTELLIGENCE which I proposed a year ago. But I don’t think we want to go over all that again, do we?


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