The brain is a fragile mass of cells, so all that remains of Neanderthals are empty skulls: it is impossible to know directly how their brains were made and how our modern human gray matter is distinguished from them. But researchers at the Max-Planck Institutes in Germany have identified a difference between our genome and that of Neanderthals that could be a clue to increased cognitive abilities compared to our missing cousin. Their work has just been published in the journal Science.
« En 2014, Svante Paabo [Institut Max-Planck, Leipzig]with whom we collaborated, published the complete genome sequence of a Neanderthal from Siberia, in which a gene had been identified as a possible candidate to explain a brain development different from that ofA wise man », recounts Wieland Huttner (Max-Planck Institute, Dresden), specialist in the human brain and last author of this new study. This gene is responsible for the production of a protein – named TKTL1 – with only one difference between these two species of the genus Homo : in the chain of amino acids that make up TKTL1, a lysine, present in Neanderthals, has been replaced in sapiensby an arginine.
A mutation certainly punctual but whose consequences are not to be minimized. Already, in 2020, Wieland Huttner’s team had published the case of another gene that showed only one change between species of the genus Homo and non-human primates. However, this simple protein variation has made it possible to explain the difference in size between human brains, which are larger than those enclosed in monkey skulls.
A tenfold production of neurons
Nevertheless, even though they have brains of comparable size, sapiens and Neanderthal may not have similar cognitive abilities. Indeed, the TKTL1 protein is particularly abundant in the frontal part of the cerebral neocortex, also more commonly called “gray matter”. And according to the results obtained by the German team, the mutation observed in TKTL1 would promote a tenfold production of neurons during the development of our brain.
More precisely, the protein would play a role in the metabolic pathways at the origin of neural progenitor cells, cells which, by dividing, form neurons. “There are two classes of progenitor cells in particular: intermediate cells and radial glial cells.explains Anneline Pinson, postdoctoral researcher and first author of the study. While the former divide only once to lead to two neurons, the latter divide asymmetrically into one neuron and a new progenitor cell. They thus proliferate for several cycles and make it possible to produce many more neurons. »
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