Evolution: more genomic evidence of pre-planning Part One (Evolution)

by dhw, Saturday, April 10, 2021, 16:55 (1111 days ago) @ David Turell

This thread is getting overloaded, and I’ll try to condense it eventually!

DAVID: We agree brains enlarged. Your point is from need, but you have never explained why need produced more expansion than needed at the time point of expansion.

dhw: I don’t know how often you want me to repeat that the initial requirements did NOT produce more expansion than needed at the time! That makes no sense! The new requirements would have triggered the expansion needed for their fulfilment and no more than that. From then on, either there was stasis (no more special requirements) or additional requirements could be dealt with by complexification until more cells were needed. That would explain erectus’s expansion, but as sapiens could not expand any more, the brain’s powers of complexification took over. And complexification proved so efficient that previously essential cells were no longer needed (shrinkage).

DAVID: The bold is not a fact but your repeated theory. The shrinkage makes the point that God gave us a brain sufficient for all future needs. If we added another 200 cc (as in our difference with erectus) we could easily handle the new hat size with our current structure. This directly relates to the language discussion below.

Yes, it is a theory. Nobody knows the facts. But we know that the brain did not expand any more, and complexification took over. What is your explanation? The shrinkage makes the point that after complexification, certain cells became redundant. According to you, your God gave us a brain that was MORE than sufficient for our needs! Why? Yes, we could handle the new hat size, so it makes perfect sense that the now missing cells were necessary when they were first added, and the skull and the rest of our anatomy had adapted to the new size.

dhw: You have now kindly provided us with three articles, all of which confirm that earlier expansion took place in the same areas with the same functions as our own. I will edit the various quotes:

EDITED QUOTES: Cranio-cerebral topography reveals that the earliest members of the genus Homo had a primitive frontal lobe organization. […] Endocranial shape change associated with frontal lobe reorganization reveals differential expansion of the inferior prefrontal cortex and also of the posterior parietal and occipital cortex. (dhw’s bold)

QUOTE: In modern human brains, the inferior frontal lobe is an important neurofunctional substrate for advanced social cognition, toolmaking and tool use, and articulated language. We may thus ask whether its evolutionary reorganization around 1.7 to 1.5 Ma was accompanied by major changes in technocultural performance.

dhw: The answer is that they were, and any of these could have triggered the expansions.

DAVID: Or the result of it. Still chicken or egg.

Correct. Nobody knows, and that is why we have all the different theories. That is why I am testing my own against the findings of all these professionals. So far it has passed with flying colours.

QUOTE: We hypothesize that this pattern reflects interdependent processes of brain-culture coevolution, where cultural innovation triggered changes in cortical interconnectivity and ultimately in external frontal lobe topography. [dhw’s bold] On the other hand, the cerebral innovations that characterize Homo at ~1.5 Ma might have constituted the foundations of the “language-ready” brain of later Homo species. [David’s bold]

dhw: You could hardly have a clearer confirmation of the process I have been describing. The brain did not expand or complexify in advance of innovation: the changes were triggered by innovation. And the brain changes would have progressively led to the language-ready brain – not just of sapiens but of earlier homos, as confirmed here:

DAVID: But you skip over the language ready comment, my bold which makes my point.

Your point has always been that major changes were necessary to mouth, lips, larynx and the vocal organs to allow for sapiens speech. The bold emphasizes that 1.5 million years ago the cerebral innovations might have constituted the foundations of our language-ready brain. In other words, there was no great leap from zilch to sapiens speech, but a gradual refinement of existing structures.

QUOTE: "Terrence Deacon proposed that the frontal lobe is the developmental and cognitive key to human language ability. If so, frontal lobe expansion implies that hominid language abilities may be quite old, perhaps predating the toolmaking abilities that appear in stone artifacts at least 2.4 million years old.

DAVID: The bold in this quote again supports my point, enlarged and complex, but waiting to be used.

They were NOT as enlarged and as complex as ours – they laid the foundations! Please read the articles you quote: “Increases in the frontal lobe appear in Australopithecus africanus and all subsequent hominid brains.” Africanus brain capacity was about 400-500 cc. Now all of a sudden you think the mechanism for sapiens language was waiting to be used!
(Continued in Part Two)