A new study of vocalization in birds sheds possible light on the relationship between voice and movement in humans and other mammals:
The upshot of this study, as described in Science Daily, is that neural pathways affecting basic motor control hold the key to the neurology of birdsong — and quite possibly of speech in humans as well. If areas in charge of movement in three distantly related avian taxa share many functional similarities with the brain areas for singing, then brain pathways used for vocal learning in humans may have evolved out of the brain pathways used for motor control.
This study may also explain why humans talk by gesture and by voice, but chimps talk only with their hands. "In its most specialized way, spoken language is the ability to control the learned movements of our larynx," senior author Erich Jarvis told Science Daily. "It's possible that human language pathways have also evolved in ways similar to these birds. Perhaps the evolution of vocal learning brain areas for birds and humans exploited a universal motor system that predates the split from the common ancestor of birds and mammals."
According to National Institutes of Health Director Elias A. Zerhouni, "The discovery that vocal learning brain pathways are embedded in the parts of the brain that control body movement offers unexpected insights on the origins of spoken language and could open up new approaches to understanding vocalization disorders in humans."
While all birds vocalize, most avian sounds are genetically dictated. Only songbirds, parrots, and hummingbirds can learn new songs. That skill resembles human speech, and the resemblance quite possibly has a shared genetic basis. Human speech may trace its origins 300 million years back to a type of vocal learning enabled by the neural pathways of stem amniotes, the common ancestor of reptiles, birds, and mammals.
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