The modern human is way better cognitively than Neanderthals, study finds

“We found that with the Neanderthal-type of amino acid in TKTL1, fewer basal radial glial cells were produced than with the modern human-type and, as a consequence, also fewer neurons,” Anneline Pinson, the lead author of the study and researcher in the Wieland Huttner group said in the statement.

"This shows us that even though we do not know how many neurons the Neandertal brain had, we can assume that modern humans have more neurons in the frontal lobe of the brain, where TKTL1 activity is highest than Neanderthals."

Modern humans have more neurons

The researchers investigated the relevance of these impacts to the human brain's growth. In order to achieve this, they used human brain organoids—miniature organ-like structures that can be grown from human stem cells and mimic aspects of early human brain development—to swap out the arginine in modern human TKTL1 for the lysine characteristic of Neanderthal TKTL1.

Additionally, the researchers discovered that modern human TKTL1 affects metabolism by stimulating the pentose phosphate pathway and then increasing fatty acid production. In this manner, it is hypothesized that modern human TKTL1 increases the synthesis of specific membrane lipids required to produce the protracted process of basal radial glial cells that drives their proliferation and, thus, increases the creation of neurons.

“This study implies that the production of neurons in the neocortex during fetal development is greater in modern humans than it was in Neanderthals, in particular in the frontal lobe,” summarizes Wieland Huttner, who supervised the study.

"It is tempting to speculate that this promoted modern human cognitive abilities associated with the frontal lobe."

Study 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.