Asymmetric Broca's area in great apes

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Abstract
A region of the ape brain is uncannily similar to one linked with speech in humans. Brodmann's area 44 delineates part of Broca's area within the inferior frontal gyrus of the human brain and is a critical region for speech production1,2, being larger in the left hemisphere than in the right1,2,3,4 — an asymmetry that has been correlated with language dominance2,3. Here we show that there is a similar asymmetry in this area, also with left-hemisphere dominance, in three great ape species (Pan troglodytes, Pan paniscus and Gorilla gorilla). Our findings suggest that the neuroanatomical substrates for left-hemisphere dominance in speech production were evident at least five million years ago and are not unique to hominid evolution.