"When we see alterations in a gene network that correspond to functional changes in the genome, it implies that these differences are very meaningful," said Oldham. "This finding supports the theory that variations in the DNA sequence contributed to human evolution."
Relying on a new analytical approach developed by corresponding author Steve Horvath, UCLA associate professor of human genetics and biostatistics, the UCLA team used data from DNA microarrays vast collections of tiny DNA spots -- to map the activity of virtually every gene in the genome simultaneously. By comparing gene activity in different areas of the brain, the team identified gene networks that correlated to specific brain regions. Then they compared the strength of these correlations between humans and chimps.
Many of the human-specific gene networks identified by the scientists related to learning, brain cell activity and energy metabolism.
"If you view the brain as the body's engine, our findings suggest that the human brain fires like a 12-cylinder engine, while the chimp brain works more like a 6-cylinder engine," explained Geschwind. "It's possible that our genes adapted to allow our brains to increase in size, operate at different speeds, metabolize energy faster and enhance connections between brain cells across different brain regions."
Future UCLA studies will focus on linking the expression of evolutionary genes to specific regions of the brain, such as those that regulate language, speech and other uniquely human abilities.