A new study says that it wasn't a bigger brain but a more sophisticated wiring that gave humans the edge to evolve beyond their closest cousins, the chimps.
Human and chimp brains are anatomically similar because both evolved from the same ancestor millions of years ago. But where does the chimp brain end and the human brain begin?
A University of California Los Angeles (UCLA) study pinpoints the unique human patterns of gene activity in the brain that could shed light on how we evolved differently than our closest relative, the journal Neuron reports.
These genes' identification could improve understanding of human brain diseases such as autism and schizophrenia, as well as learning disorders and addictions, according to a California statement.
"Scientists usually describe evolution in terms of the human brain growing bigger and adding new regions," said principal investigator Daniel Geschwind, professor of human genetics and neurology at the David Geffen School of Medicine at UCLA.
"Our research suggests that it's not only size but the rising complexity within brain centres that led humans to evolve into their own species," said Geschwind.
Using post-mortem brain tissue, Geschwind and colleagues applied next-generation sequencing and other modern methods to study gene activity in humans, chimps and rhesus macaques, a common ancestor for both chimps and humans that allowed the researchers to see where changes emerged between humans and chimpanzees.