How modern human brains are different from those of other hominids and chimps.

Work pointed to in the previous post continues to add to the list of behaviors once presumed to be unique to humans that have now been found in other animals (morality, having a ‘self’, etc.) Previous MindBlog posts (list, von Economo neurons etc. do search..) have noted emerging evidence for brain features unique to - or much more pronounced in - humans than other primates. Now Pinson et al. have found that a single amino acid change in the transketolase-like 1 (TKTL1) protein on production of basal radial glia, the workhorses that generate much of the neocortex, appears that the modern human has more neocortex to work with than the ancient Neanderthal did. Here is their abstract:

Neanderthal brains were similar in size to those of modern humans. We sought to investigate potential differences in neurogenesis during neocortex development. Modern human transketolase-like 1 (TKTL1) differs from Neanderthal TKTL1 by a lysine-to-arginine amino acid substitution. Using overexpression in developing mouse and ferret neocortex, knockout in fetal human neocortical tissue, and genome-edited cerebral organoids, we found that the modern human variant, hTKTL1, but not the Neanderthal variant, increases the abundance of basal radial glia (bRG) but not that of intermediate progenitors (bIPs). bRG generate more neocortical neurons than bIPs. The hTKTL1 effect requires the pentose phosphate pathway and fatty acid synthesis. Inhibition of these metabolic pathways reduces bRG abundance in fetal human neocortical tissue. Our data suggest that neocortical neurogenesis in modern humans differs from that in Neanderthals.