Development of stem cells between modern humans and Neanderthals

To check if the Neanderthal set of amino acids has the opposite effect, the researchers then introduced the ancestral amino acids in human brain organoids – miniature organ-like structures that can be grown from human stem cells in cell culture dishes in the lab and that mimic aspect of early human brain development.

"In this case, metaphase became shorter and we found more chromosome distribution errors." According to Mora-Bermúdez, these three modern human amino acid changes in the proteins known as KIF18a and KNL1 are responsible for the fewer chromosome distribution mistakes seen in modern humans as compared to Neanderthal models and chimpanzees. He adds that "having mistakes in the number of chromosomes is usually not a good idea for cells, as can be seen in disorders like trisomies and cancer."

"Our study implies that some aspects of modern human brain evolution and function may be independent of brain size since Neanderthals and modern humans have similar-sized brains. The findings also suggest that brain function in Neanderthals may have been more affected by chromosome errors than modern humans," summarizes Wieland Huttner, who co-supervised the study.

Ref:

Felipe Mora-Bermúdez et. al, Longer metaphase and fewer chromosome segregation errors in modern human than Neanderthal brain development, Science Advances, 29-Jul-2022, 10.1126/sciadv.abn7702