How a Gene Duplication Helped Our Brains Become 'Human'

What genetic changes account for the vast behavioral differences between humans and other primates? Researchers so far have cataloged only a few, but now it seems that they can add a big one to the list. A team of researchers led by scientists has shown that an extra copy of a brain-development gene, which appeared in our ancestors' genomes about 2.4 million years ago, allowed maturing neurons to migrate farther and develop more connections.

Surprisingly, the added copy doesn't augment the function of the original gene, SRGAP2, which makes neurons sprout connections to neighboring cells. Instead it interferes with that original function, effectively giving neurons more time to wire themselves into a bigger brain.