Three gene 'flaws' made our brains grow
Seven billion brain cells mark your brain from that of a gorilla, thanks to three genes that have changed since evolution separated humans and apes.
In 14 million years, the human brain has grown from about 0.5 kg in our earliest ancestors to 1.4 kg, probably thanks to three newly-identified genes.
Californian scientists spotted the genes, when they studied how many nerve cells a macaque produces in its brain. They cultivated the animals’ brain tissue in the lab, particularly focusing on NOTCH genes, which influence the development of stem cells in embryos. The scientists discovered that humans have three active NOTCH genes on chromosome 1, which do not exist in macaques nor in our closest relatives, chimps and gorillas, i.e. the three genes are unique for humans. So, scientists can reconstruct our evolutionary history.
The first gene emerged as a partial copy of a gene on chromosome 1 some 14 million years ago, before humans parted from the other apes. 11 million years later, the gene was repaired, coinciding with the time when the human brain started to grow. Later, the gene was copied two more times. Other scientists have revealed that the three genes code for a protein that causes the stem cells of the brain to divide in four instead of two nerve cells. The result is that we produce many more nerve cells than other primates.