Scientists have traced gesticulating during speech to an ancient part of the fish brain.
"We have traced the evolutionary origins of the behavioural coupling between speech and hand movement back to a developmental compartment in the brain of fishes," said Professor Andrew Bass from Cornell University in New York.
"Pectoral appendages (fins and forelimbs) are mainly used for locomotion. However, pectoral appendages also function in social communication for the purposes of making sounds that we simply refer to as non-vocal sonic signals, and for gestural signalling," he said.
This begins to explain the ancestral origins of the neural basis for the close coupling between vocal and pectoral/gestural signalling that is observed among many vertebrate groups, including humans.
"Coupling of vocal and pectoral-gestural circuitry starts to get at the evolutionary origins of the coupling between vocalisation (speech) and gestural signalling (hand movements). This is all part of the perhaps even larger story of language evolution," Bass said.