What makes us this modern human, compared to our Neanderthal and Denisovan cousins who diverged from us at least 600,000 years ago? A team led from the Max Planck Institute of Molecular Cell Biology and Genetics has just announced an important discovery, published in Science and processed in the New York Times. By comparing the human genome and that of its two archaic cousins, they found a mutation (hTKTL1) that seems to play a major role in brain development. Something to shed new light on what the modern man has in mind.
A fascinating demonstration. The gene concerned, baptized TKTL1, was mainly studied for its contribution to tumor metabolism. But the researchers demonstrated, in mice and ferrets, that the human hTKTL1 mutation promotes the proliferation of (glial) cells involved in the construction of the frontal lobe during the development of the embryo. However, this part of the brain is associated with the most elaborate mental functions: language, analysis, decision… The last act of the demonstration is the most striking: in a human brain organoid – a sort of mini-brain in the laboratory – they demonstrated that blocking the mutation reduced the number of glial cells and neurons generated.
Why it matters. That a single mutation has such a clear role in the architecture and size of the frontal cortex is impressive in itself. Paleogeneticists believe they have found a key mechanism that may explain the supposed cognitive differences between modern humans and their more archaic cousins Neanderthals and Denisova. These remain debatedbut we know that the Neanderthal brain was longer, with a less developed frontal lobe. The comparison of genomes between modern humans and Neanderthals in 2014 highlighted 96 gap mutations. Several of them are suspected of playing a role in brain development.
