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Sunday, November 6, 2022

‘Breakthrough’ finding shows how modern humans grow more brain cells than Neanderthals

Rodrigo Pérez Ortega
Originally posted 8 SEP 22

We humans are proud of our big brains, which are responsible for our ability to plan ahead, communicate, and create. Inside our skulls, we pack, on average, 86 billion neurons—up to three times more than those of our primate cousins. For years, researchers have tried to figure out how we manage to develop so many brain cells. Now, they’ve come a step closer: A new study shows a single amino acid change in a metabolic gene helps our brains develop more neurons than other mammals—and more than our extinct cousins, the Neanderthals.

The finding “is really a breakthrough,” says Brigitte Malgrange, a developmental neurobiologist at the University of Liège who was not involved in the study. “A single amino acid change is really, really important and gives rise to incredible consequences regarding the brain.”

What makes our brain human has been the interest of neurobiologist Wieland Huttner at the Max Planck Institute of Molecular Cell Biology and Genetics for years. In 2016, his team found that a mutation in the ARHGAP11B gene, found in humans, Neanderthals, and Denisovans but not other primates, caused more production of cells that develop into neurons. Although our brains are roughly the same size as those of Neanderthals, our brain shapes differ and we created complex technologies they never developed. So, Huttner and his team set out to find genetic differences between Neanderthals and modern humans, especially in cells that give rise to neurons of the neocortex. This region behind the forehead is the largest and most recently evolved part of our brain, where major cognitive processes happen.

The team focused on TKTL1, a gene that in modern humans has a single amino acid change—from lysine to arginine—from the version in Neanderthals and other mammals. By analyzing previously published data, researchers found that TKTL1 was mainly expressed in progenitor cells called basal radial glia, which give rise to most of the cortical neurons during development.