A chance rearrangement of the human genome over a million years ago probably kick-started the evolution of modern humans from our primate ancestors. A recent study explains why human DNA contains sections, many of which are involved in brain development, that are unique to us and are not shared with even our closest relatives, chimpanzees.
These stretches of human-specific DNA are called human accelerated regions (HARs). They were discovered almost 20 years ago by Dr Katie Pollard, now director of the Gladstone Institute of Data Science and Biotechnology, who led the new study to try to figure out where they came from.
To find out which specific genes were being affected by the HARs, the team performed experiments in human and chimpanzee stem cells. As it turned out, many of the genes they identified are known to play a role in brain development. Exactly how this contributed to the evolution of the human brain is a question the team is keen to answer next.
The findings also chime with those of another recent study from the team. They reported that many of the early changes in HARs had opposing effects: an original mutation might have “turned up” associated gene activity too much, and so a further change would have been needed down the line to tweak this.
