Neanderthals are the closest relatives of modern humans. Therefore comparisons with them may provide fascinating insights into what makes present-day humans unique, for example with regard to brain development. The neocortex, the largest part of the outer layer of the brain, is unique to mammals and is important for many cognitive abilities. This expanded dramatically during human evolution in the ancestral species to both Neanderthals and modern humans, resulting in brains of similar size to both Neanderthals and modern humans. 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 neural stem cells—the cells from which the developing neurons of the neocortex derive. Modern humans spend more time preparing their chromosomes for division than Neanderthals. This results in fewer errors when chromosomes are distributed among daughter cells in modern humans than in Neanderthals or chimpanzees, and may have consequences for how Brain develops and works. This study shows cellular differences in brain development between modern humans and Neanderthals.
Neanderthals and Denisovans, the ancestors of modern humans, are about one hundred . separated amino acids, the building blocks of proteins in cells and tissues, changed in modern humans and spread to almost all modern humans. The biological significance of these changes is largely unknown. However, six of those amino acid changes occurred in three proteins that play an important role in the delivery of chromosomes, carriers of genetic information, to two daughter cells during cell division.
The influence of modern human forms on the development of the brain
To investigate the importance of these six changes to neocortex development, scientists first introduced modern human forms into mice. Mice are similar to Neanderthals in those six amino acid positions, so these changes made them a model for the developing modern human brain. Study lead author Felipe Mora-Bermudez described the discovery: “We found that three modern human amino acids in two proteins cause a long metaphase, a stage where chromosomes are produced. cell divisionand this results in fewer errors when the chromosomes are distributed daughter cells Of neural stem cellsLike modern humans.” To test whether the Neanderthal set of amino acids had the opposite effect, the researchers then introduced ancestral amino acids into the human brain — miniature organ-like structures that can be grown from human stem cells into the cell. Culture dishes in the laboratory and mimic aspects of early human brain development. “In this case, metaphase shortened and we found more chromosome distribution errors.” According to Mora-Bermudez, this shows that those three modern human amino Acid changes in proteins known as KIF18a and KNL1 are responsible for fewer chromosome distribution mistakes seen in modern humans than in Neanderthal models and chimpanzees. He adds that “mismatches in chromosome number usually occur.” Not a good idea. CellsAs can be seen in disorders such as trisomy and cancer.”
“Our study implies that some aspects of the development and function of the modern human brain may be independent of brain size because Neanderthals and modern humans have similarly sized brains. The findings also suggest that brain function in Neanderthals may stem from chromosomal errors. may be more affected. modern mansays Weiland Hutner, who co-supervised the study. Svante Pabo, who also co-supervised the study, adds that “future studies are needed to examine whether the decreased error rate affects modern Or not. human Symptoms related to brain function.”
Felipe Mora-Bermudez et al, Prolonged metaphase and fewer chromosome segregation errors in modern humans compared to Neanderthal brain development, science progress (2022). DOI: 10.1126/sciadv.abn7702, www.science.org/doi/10.1126/sciadv.abn7702
Max Planck Society
Citation: Taking your time makes a difference: Brain development differs between Neanderthals and modern humans (2022, July 29) 30 Jul 2022 https://phys.org/news/2022-07-difference-brain-differs Retrieved from -neanderthals-mod.html
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