A recent article in Nature Neuroscience describes how species-specific calls activate homologs of Broca's (speech generation) and Wernicke's (speech comprehension) areas in the macaque monkey. The authors identified neural systems associated with perceiving species-specific vocalizations in rhesus macaques using positron emission tomography (PET). These vocalizations evoked distinct patterns of brain activity in homologs of the human perisylvian language areas. Rather than resulting from differences in elementary acoustic properties, this activity seemed to reflect higher order auditory processing. Their finding suggests the possibility that the last common ancestor of macaques and humans, which lived 25–30 million years ago, possessed key neural mechanisms that were plausible candidates for exaptation during the evolution of language.
Figure, Broca's area of the human brain (on the right) includes Brodmann's area 44. The macaque brain (on the left, actually smaller than a human brain) has a corresponding area.