Big brain evolution: changes in sapiens skull shape;addendum (Evolution)

by David Turell @, Tuesday, October 15, 2019, 20:17 (346 days ago) @ David Turell

A new study that raises the same old question: how did skull size and shape coordinate with brain growth in size, since bone is hard and brain is very soft:

https://phys.org/news/2019-10-brain-independently-braincase-evolution.html

"The human brain is about three times the size of the brains of great apes. This has to do, among other things, with the evolution of novel brain structures that enabled complex behaviors such as language and tool production. A study by anthropologists at the University of Zurich now shows that changes in the brain occurred independent of evolutionary rearrangements of the braincase.

"The human brain is like a fish in an aquarium, floating inside the liquid-filled braincase—but filling it out almost completely. The relationship between the brain and the braincase, and how they interacted during human evolution, has been occupying the minds of researchers for almost a century. They addressed this question by studying brain-braincase relationships in our own species, and in our closest living relatives, the great apes.

***

"The results show that the characteristic spatial relationships between brain and bone structures in humans are clearly distinct to those in chimpanzees. While the brain and its case continued to evolve side by side, they did so along largely independent evolutionary paths. (Note this does explain the problem of coordinating size.)

"For example, brain structures related to complex cognitive tasks such as language, social cognition and manual dexterity expanded significantly in the course of human evolution. This becomes visible as a shift of the neuroanatomical boundaries of the frontal lobe of the brain. This shift, however, did not affect the bony structures of the braincase. Instead, changes in the braincase largely reflect adaptations to walking upright on two legs, or bipedalism. For example, the opening at the skull base for the spinal cord moved forward during human evolution in order to optimize balance of the head atop the vertebral column. However, these evolutionary changes to the braincase did not have an effect on our cerebral structures." (This bold shows the necessary positional changes for bipedalism)

Comment: Still no solution as to how the size changes were coordinated. Soft brain enlarging cannot push hard bone to enlarge.


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