What would they say if they could speak?
This is the finding of a pair of researchers in Atlanta, Georgia, US, who carried out magnetic resonance imaging (MRI) scans on chimpanzees, bonobos and gorillas.
They say they were surprised no-one had looked for the crucial lopsided structure in great apes before.
The discovery could imply that evolution of brain structures linked to speech began before the ancestors of humans and apes parted ways.
Puzzling discrepancy
Brodmann's area 44 is part of the Broca's area in the human brain.
It is critical for speech production and it is larger in the left hemisphere than in the right.
Claudio Cantalupo and William Hopkins of Emory University and Georgia State University were puzzled by the fact that the apes had a similar structure, but obviously could not speak.
"The part possession by great apes of a homologue of Broca's area is puzzling, particularly considering the discrepancy between sophisticated human speech and the primitive vocalisations of great apes," they write in the journal Nature.
Right-handed apes
"This may be explained by the contribution that gestures have made to the evolution of human language and speech," they speculate.
Captive great apes tend to gesture with their right hands, especially when making some kind of vocal noise, they note.
Their theory is that as the ancestors of humans and great apes learned to grunt and gesticulate, the left side of their area 44s grew larger.
However, it appears that for some reason grunting and gesturing went on to become language in humans, but not in the apes.