Uncovering the Catalyst for Human Brain Evolution
A new study suggests that the genes for large brain size in humans emerged from random mutations in DNA sequences called human accelerated regions (HARs), which act as gene enhancers controlling brain formation during embryonic development. The study found that 30% of HARs in humans were in areas of the genome where the DNA was folded differently, indicating that structural variations in the human genome likely came from a random mutation during reproduction. This theory suggests that human large brain size occurred by discontinuous random mutation, which was then selected for, rather than natural selection gradually acting on normal variation in brain size.