Bonobos, our amorous primate relatives, communicate much like human infants do, according to a new study.
Many species only make sounds related to certain events or emotional states — fear when a predator is spotted, for example, or excitement when food is discovered.
Researchers from the University of Birmingham in the U.K. and the University of Neuchatel in Switzerland found that bonobos observed in Congo acted differently.
The great apes often made high-pitched "peep" calls in neutral situations, like between feeding or traveling, indicating the sounds were made independent of the animals' emotional state. They were similar to the "protophones" — sounds made before speech is developed — made by human infants.
"We felt that it was premature to conclude that this ability is uniquely human, especially as no one had really looked for it in the great apes," Zanna Clay, a psychology researcher at the University of Birmingham, said in a statement. "It appears that the more we look, the more similarity we find between animals and humans."
Those "peep" calls could represent a bridge, researchers said, between the "functionally fixed animal vocalizations" of most creatures and human speech.
The research was published Tuesday in the journal PeerJ.