Was the evolution of spoken language more of a song or a dance? The responses of chimpanzees to a stuffed snake suggest it might have been more like a stage show, with vocal and gestural modes of communication both being fundamental building blocks of language.
Darwin suggested we sang our way to modern language, gradually moving from vocal flourishes designed to attract mates to primitive vocal communication that eventually developed into speech.
But evidence from other apes has suggested that our ancestors’ vocal cries were involuntary and strongly linked to emotions, whereas their hand gestures were the more intentional means of communication. That seemed to suggest language might have blossomed from gestural communication.
Not satisfied with the idea that chimps’ vocal signals are involuntary, Katie Slocombe from the University of York, UK, and her colleagues stuffed the skin of a dead snake and placed it in a forest in Uganda. Using a fishing line, they wiggled the snake when chimpanzees came near and observed and categorised the ensuing alarm calls.