Neuroanatomical correlates of attention-getting sounds in captive chimpanzees: towards understanding the evolution of flexible, learned, vocal communication Open Access
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Despite manifold hypotheses on language evolution, the neurobiological origins of the human capacity to speak remain little understood. In particular, it is unknown how humans developed a sophisticated capacity for vocal learning, while other primates have only limited control over their vocal, communicative signals. To better understand the neurobiological origins of human vocal flexibility, I used non-invasive, in vivo neuroimaging techniques, and post-mortem histological and molecular analyses to examine structural differences in the brain from a population of captive chimpanzees, which display variation in the capacity to produce learned, voluntarily controlled vocalizations to attract attention (attention-getting vocalizations). Results suggested differences between chimpanzees that produce versus those that do not produce attention-getting sounds in grey matter distribution, white matter connectivity, volume of subcortical structures (i.e., striatum), and expression levels of FOXP2, a transcription factor that has been suggested to have played a role in the evolution of speech and language. As studies on the neurobiological origins of speech have been mostly conducted on experimental species (i.e, songbirds, mice) that are evolutionarily distant from humans, investigating vocal flexibility in chimpanzees, humans’ closest living relatives, may help identify precursors to speech within the primate lineage.