Evolution and humans: big brain size or use (Evolution)

by dhw, Sunday, June 25, 2017, 14:38 (2706 days ago) @ David Turell

DAVID: A review article of Homo brain development from studies in embryogenesis. The entire article should be read for full understanding and traces preliminary changes for upright posture back to about 39 million years ago, involving changes to the base of the skull which are required for bipedalism:
http://inference-review.com/article/the-last-threshold

QUOTE: New manual chains of operation reflect a symbolic and conceptual level of thought attributed to the brain of the genus Homo. My suggestion is that the emergence of these capacities should be broadened to encompass the hominin stage, denoted by the verticalization of the cerebellum, such as for Australopithecus, Kenyanthropus, and Paranthropus. Although their brains were smaller than that of Homo habilis, they may have been capable of conceptual and creative innovations. Passing those first thresholds made possible the creative expression of ideas and concepts. (DAVID’s bold)

DAVID’s comment: Absolutely, size first, use second! God's preplanning at work! Note my bold. All of my theories come from this article among others. Don't think I've presented this before.

“Size first, use second” is fair enough, since we now know that by use you mean nothing more than material implementation of immaterial thought. There is no doubt the author believes that the brain is the source of thought, including – interestingly – conceptual and creative innovations well before homo habilis. She may well be right. I’m not taking sides in the materialism v dualism debate. Complexification of the nervous system and the verticalization of the skull seem to be her keys to the emergence of Homo sapiens, but I can’t find any indication as to why she thinks this actually took place. She starts with a brief sideswipe at religion, but there’s no mention of God’s planning/dabbling (so I don’t know about “all” your theories), or of random mutations, or of cell communities working it out for themselves. Her causal theory stops at nerves and the base of the skull.

A couple more quotes that I found very interesting:
QUOTE: “Darwin and his contemporaries were themselves part of the Lamarckian revolution. A function gives rise to an organ and then the organ, including the shape of its bone tissues, is gradually modified. Those changes are then, through use, transmitted to later generations.”

This leaves out Darwin’s random mutations, but it’s a view that ties in with the hypothesis that physical changes take place in response to needs or opportunities, and not in anticipation of them. Malassé then refers to Arambourg:

“Arambourg was not a neo-Darwinian. He was a punctualist, a saltationist, and a Lamarckian:
The well-known facts of morphological convergence in groups with very diverse origins, but living in identical environments, seems to me to be difficult to explain, other than by a certain action of the environment, that is to say by the intervention of a “Lamarckian” cause.”

I must say I find this explanation very appealing, but Malassé rejects it:

MALASSÉ: These embryological details have dramatic consequences. The emergence of upright hominid posture need no longer be linked to habitat changes. Its origin must be attributed to the increasing complexity of the nervous system. The embryonic body plan was reorganized through a series of threshold effects which are still in evidence in every human embryo.

And this is where, in the context of our discussions, it might have been interesting to know what she regards as the cause of the increasing complexity and the resultant upright posture.