An intelligence gene
3.2-2.5 million years ago
A gene called SRGAP2 was duplicated three times. As a result, our ancestors had several copies, some of which could evolve freely. One of the mutated copies turned out to be better than the original. It seems to have caused our brain cells to extrude more spines, allowing them to form more connections.
See other: What Makes Humans Human?
Knowledge Guild 