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

by David Turell , Thursday, April 08, 2021, 22:14 (1323 days ago) @ David Turell

A careful study of early Homo brain cases raises interesting issues:

https://science.sciencemag.org/content/372/6538/165?utm_campaign=toc_sci-mag_2021-04-08...

Pattern and timing of brain reorganization in early Homo

Cranio-cerebral topography reveals that the earliest members of the genus Homo had a primitive frontal lobe organization, featuring an ape-like anterior location of the inferior precentral sulcus relative to the coronal suture. Our data indicate that the derived frontal lobe organization emerged relatively late during the evolution of Homo, between 1.7 and 1.5 Ma—not at the transition from Australopithecus to Homo, but clearly later than the first dispersals of Homo from Africa. 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. This pattern indicates that the anterior and posterior cortical association areas evolved in tandem rather than in sequence. We infer from this that endocasts of early Homo predating frontal lobe reorganization potentially exhibit imprints of remnant ape-like lunate sulci in the parieto-occipital region. (my bold)

Comment: This paragraph tells us our frontal lobes started out in a primitive form but enlargement was all over the organ all at once as the bold indicates.

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Neurofunctional implications

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. The earliest evidence for Mode II (Acheulean) technocultures in Africa largely coincides with incipient frontal lobe reorganization, and Mode I and Mode II lithic technologies were used concurrently during the critical time period. 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. 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. (my bold)

Comment: As we have discussed brain enlargement is associated with new artifacts and the authors imply that new uses caused changes in brain shape, but not size. And my bold shows the authors were certainly aware of what we refer to as stasis with future use coming later, while obviously the new-sized brain is prepared for it..