Homo Sapiens 'defeated' Neanderthals with a single amino acid

Neanderthals and modern humans have the same brain size, but Homo sapiens were more adaptable.

Researchers have shown that replacing just one amino acid is critical to brain development.

Modern humans and extinct related species,Neanderthals and Denisovans differ in several proteins that use different amino acid sequences (building blocks). One of them is TKTL1, which affects the development of the brain.

In modern humans, TKTL1 contains the amino acidarginine, and in Neanderthals it is related - lysine. The study showed that a large amount of this protein is found in progenitor cells of the human fetal neocortex. These are the building materials from which all the neurons of the cerebral cortex originate. At the same time, the highest concentration is observed in the progenitor cells of the frontal lobe.

The difference in the number of progenitor cells and neurons between Neanderthals and Homo sapiens. Image: Anneline Pinson et al., Science

The researchers used organoids −artificially grown organ models to test how amino acid substitution affects brain development. It turned out that when using a protein containing lysine, as in Neanderthals, fewer basal radial glial cells are produced and, therefore, fewer neurons.

Similar results were obtained with the introductionmodified protein into mouse brain cells. The researchers believe that due to the replacement of one protein in Homo sapiens, more neurons formed, especially in the frontal lobe of the brain. It is these areas that are responsible for conscious movement, speech and planning. Such evolutionary development created an advantage in the cognitive functions of the ancestors of modern people over the disappeared "relatives".

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