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Taking your time makes a difference – Brain development differs between Neanderthals and modern humans

Dresden and Leipzig researchers find that stem cells in the developing brain of modern humans take longer to divide and make fewer errors when distributing their chromosomes to their daughter cells, compared to those of Neanderthals.

Neanderthals are the closest relatives to modern humans. Comparisons with them can therefore provide fascinating insights into what makes present-day humans unique, for example regarding the development of the brain. The neocortex, the largest part of the outer layer of the brain, is unique to mammals and crucial for many cognitive capacities. It expanded dramatically during human evolution in species ancestral to both Neanderthals and modern humans, resulting that both Neanderthals and modern humans having brains of similar sizes. However, almost nothing is known about how modern human and Neanderthal brains may have differed in terms of their development and function. Researchers from the Max Planck Institute of Molecular Cell Biology and Genetics (MPI-CBG) in Dresden and the Max Planck Institute for Evolutionary Anthropology (MPI-EVA) in Leipzig have now discovered that neural stem cells – the cells from which neurons in the developing neocortex derive – spend more time preparing their chromosomes for division in modern humans than in Neanderthals. This results in fewer errors when chromosomes are distributed to the daughter cells in modern humans than in Neanderthals or chimpanzees, and could have consequences for how the brain develops and functions. This study shows cellular differences in the development of the brain between modern humans and Neanderthals.

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Fewer chromosome segregation errors in modern human than Neanderthal neural stem cells. Left side: microscopy image of the chromosomes (in cyan) of a modern human neural stem cell of the neocortex during cell division. Right side: same type of image, but of a cell where three amino acids in the two proteins KIF18a and KNL1, involved in chromosome separation, have been changed from the modern human to the Neanderthal variants. These “neanderthalized” cells show twice as many chromosome separation errors (red arrow). © Felipe Mora-Bermúdez / MPI-CBG