I am very impressed with the number of substitutions on the human lineage compared with other vertebrates. The region is highly conserved: only two bases are different between chimpanzees and chickens. In contrast, there have been 18 substitutions on the human lineage! It's like every other species is driving the same Plymouth Reliant, and humans are driving a Ferrari!

We devised a ranking of regions in the human genome that show significant evolutionary acceleration. Here we report that the most dramatic of these 'human accelerated regions', HAR1, is part of a novel RNA gene (HAR1F) that is expressed specifically in Cajal-Retzius neurons in the developing human neocortex from 7 to 19 gestational weeks, a crucial period for cortical neuron specification and migration. HAR1F is co-expressed with reelin, a product of Cajal-Retzius neurons that is of fundamental importance in specifying the six-layer structure of the human cortex.