The developmental and evolutionary mechanisms behind the emergence of 
human-specific brain features remain largely unknown. However, the recent 
ability to compare our genome to that of our closest relative, the chimpanzee, 
provides new avenues to link genetic and phenotypic changes in the evolution of 
the human brain. 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. HAR1 and the other human accelerated 
regions provide new candidates in the search for uniquely human biology.