Human evolution; neonatal human and Neanderthal brains (Introduction)

by David Turell , Saturday, December 14, 2019, 05:08 (1804 days ago) @ David Turell

The development is different:

https://www.sciencedirect.com/science/article/pii/S0960982210012820?dgcid=raven_sd_reco...

"Summary:
Neanderthals had brain sizes comparable to modern humans, but their brain cases were elongated and not globular as in Homo sapiens. It has, therefore, been suggested that modern humans and Neanderthals reached large brain sizes along different evolutionary pathways. Here, we assess when during development these adult differences emerge. This is critical for understanding whether differences in the pattern of brain development might underlie potential cognitive differences between these two closely related groups. Previous comparisons of Neanderthal and modern human cranial development have shown that many morphological characteristics separating these two groups are already established at the time of birth, and that the subsequent developmental patterns of the face are similar, though not identical. Here, we show that a globularization phase seen in the neurocranial development of modern humans after birth is absent from Neanderthals.

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"After the constraints on neonatal shape and size imposed by the shape of the birth canal of the female pelvis are relaxed, the two species develop along different pathways.

"The difference between the developmental patterns of modern humans and Neanderthals is most prominent directly after birth, when the shape of the vault is extremely sensitive to the tempo and mode of brain growth. When the cranial bones are thin and not yet fully ossified, the shape changes of the frontal and parietal bone are largely driven by the increase in brain volume. While the growth of the face affects the shape of the cranial base it is unlikely that this alone could explain the shape changes of the parietal and occipital bone shown in Figure 1. We suggest, therefore, that species differences in brain growth rates and timing underlie the uniquely modern human globularization phase.

"We suggest, therefore, that species differences in brain growth rates and timing underlie the uniquely modern human globularization phase.

"The development of cognitive abilities during individual growth is linked to the maturation of the underlying neural circuitry: in humans, major internal brain reorganization has been documented until adolescence, and even subtle alterations of pre- and perinatal brain development have been linked to changes of the neural wiring pattern that affect behavior and cognition. The uniquely modern human pattern of early brain development is particularly interesting in the light of the recent breakthroughs in the Neanderthal genome project, which identified genes relevant to cognition that are derived in living humans. We speculate that a shift away from the ancestral pattern of brain development occurring in early Homo sapiens underlies brain reorganization and that the associated cognitive differences made this growth pattern a target for positive selection in modern humans."

Comment: Essentially our brains develop quite differently and may represent better cognition in humans. All of this evidence supports the idea we were the final goal of evolution.