Could a lopsided gap help set us apart from our primate cousins? Our brains and chimps' are built differently in the areas that give us our social skills and language.
The human brain has a 4.5-centimetre-long groove running deeper along the right side than the left. Chimp brains lack this asymmetry, as François Leroy of the French National Institute of Health and Medical Research in Saclay, and colleagues, have discovered. The groove's function is unknown, but its location suggests it played a role in the evolution of our communication abilities. "One day this will help us understand what makes us tick," says Colin Renfrew of the University of Cambridge, who was not involved in the study.
Although our brain is about three times the size of a chimp's, anatomical features that only the human brain possesses are surprisingly hard to find. One known difference is in a region called Broca's area, which is also involved in speech and is larger in humans than chimps.
The asymmetrical groove in humans was also known, but the new study, in which 177 people and 73 chimps had brain scans, revealed it is almost completely absent in other primates.
Rejig on the right
In humans, the deeper groove in the right brain lies in the region that controls voice and face recognition and working out what other people are thinking – our so-called theory of mind. The shallower groove on the left is at the heart of the areas associated with language. The lack of symmetry could signify that tissue layers in the right brain have been reorganised, says Leroy.
"Asymmetrical brain landmarks may be key features to understand what is so specific in our species," says Leroy, since left and right sides of the human brain tend to perform different tasks. "We think that [this asymmetry] is related to either speech or social cognition, which are both abilities for which humans outperform other primates."
Another avenue for research could be to look at which genes are active in forming this region in the developing embryos of primates, says Leroy.
Journal reference: PNAS, DOI: 10.1073/pnas.1412389112
If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.
