London, August 13 (ANI): A new study has found that a brain region critical to speech and language ballooned after humans split from chimpanzees, which explains why humans can talk and chimps can't.
Named after French physician, Pierre Paul Broca, who identified the region in two brain-damaged patients incapable of uttering more than a few words, Broca's area usually occupies a much larger portion of the left half of the human brain than the right.
Because right-handed humans also tend to process language in their left halves, some researchers think that lop-sidedness in Broca's area may help explain why humans alone developed language.
"There must be something unique about the wiring of the region" to explain language, said Chet Sherwood, a neuroscientist at George Washington University in Washington DC, who led the new study.
However, brain-imaging studies have hinted that Broca's area also tends to be larger in one half of the chimpanzee brain than the other.
What's more, this area kicks into action when chimps communicate via hand gestures, another study found.
According to a report in New Scientist, to get a better handle on how Broca's area may have changed in the 6 million years since humans and chimpanzees last shared a common ancestor, Sherwood's team examined thin sections of Broca's area, collected from 12 chimpanzees after they died of natural causes.
The researchers noticed a lot of differences between individual chimpanzees in the size, location and symmetry of Broca's area.
But, Sherwood's team found no common population-wide differences in the number of neurons in the left and right Broca's area for chimpanzees, as is the case in humans.
Furthermore, the handedness of the chimpanzees - established before their deaths - wasn't related in any way to the brain region's symmetry.
Broca's area has also swelled disproportionately during our species' evolution. Human brains are 3.6 times larger than those of chimpanzees, on average.
Yet, Broca's area is more than 6 times larger in humans than chimpanzees, according to Natalie Schenker, a neuroscientist now at the University of California, San Diego, who led the study along with Sherwood.
"It suggests that Broca's area is doing something that's important," she said. "Maybe it's taken on some increased functionality," she added.
"I buy the conclusion that Broca's area underwent changes in hominins in conjunction with language evolution," said Dean Falk, an anatomist at Florida State University in Tallahassee. (ANI)