Although the brain's frontal lobes are believed to be critical for high-level thinking, they are not the sole source of human intelligence, according to a new study.
Researchers from the University of Reading and Durham University in the United Kingdom found other regions of the brain, such as the cerebellum, played an unexpected but essential role in the expansion of the human brain. These areas of the brain should get more attention because they are not only involved in cognition (mental abilities) but also disorders, such as autism and dyslexia, the study authors pointed out.
"Probably the most widespread assumption about how the human brain evolved is that size increase was concentrated in the frontal lobes," study lead author Robert Barton, from the anthropology department at Durham, explained in a university news release.
"It has been thought that frontal lobe expansion was particularly crucial to the development of modern human behavior, thought and language, and that it is our bulging frontal lobes that truly make us human," he said. "We show that this is untrue: Human frontal lobes are exactly the size expected for a non-human brain scaled up to human size."
Barton added that other areas of the brain considered to be more primitive, such as the cerebellum, were just as important during human evolution.
How the study was done
In conducting the study, the researchers examined data from previous human and animal studies. Using a new method, they analysed the speed of evolutionary change. The investigators found human frontal lobes did not evolve particularly fast after the split from chimpanzee lineage.
Rather than the size of the frontal lobes, the study authors suggested higher human intelligence is the result of extensive brain networks linking many different parts of the brain. The structure of these networks may be more critical for intelligence than the size of one region of the brain.
The study was published in the Proceedings of the National Academy of Sciences.
The U.S. National Institute of Neurological Disorders and Stroke has more about the brain and how it works.