The Gene That Makes Us Human
A rapidly evolved piece of DNA that’s unique to humans could be the key to the human brain
SOURCE: “An RNA Gene Expressed during Cortical Development Evolved Rapidly in Humans”
Katherine Pollard et al.
Nature 443(7108): 167-172
RESULTS: Researchers identified a small piece of DNA that has undergone rapid evolution in humans but not in other species, such as chickens and chimpanzees. The DNA sequence is part of a gene that codes for RNA rather than for a protein; the gene is expressed during development of the cerebral cortex.
WHY IT MATTERS: The human brain is three times the size of a chimp’s–largely because of a bigger cerebral cortex, the outer layer of the brain that is responsible for reasoning and other types of complex thought. Because the newly identified variation is unique to humans, and the gene it is part of is active during cortical development, the finding might help explain how the human brain evolved.
METHODS: Researchers compared the human genome with the genomes of chimps, dogs, rats, mice, and chickens to find genetic sequences that changed little between species, suggesting that they were functionally important. Within those shared regions, the researchers looked for sequences that had changed significantly between chimpanzees and humans, indicating that those changes played a crucial role in human evolution.
NEXT STEPS: Researchers will try to better understand the RNA gene’s role in brain development and cognition by creating a mouse that expresses the human form of the gene.