A new study reveals wild bonobos, which are our closest living relatives, talk like babies.

Scientists observed these primates using a high-pitched call type, or "peep," to communicate, the University of Birmingham reported. The meaning of these calls is altered depending on the context, and resembles the independent manner in which human babies communicate. These peeps do not vary acoustically, even across positive and neutral circumstances, which is the same case for human infants.

"When I studied the bonobos in their native setting in Congo, I was struck by how frequent their peeps were, and how many different contexts they produce them in. It became apparent that because we couldn't always differentiate between peeps, we needed understand the context to get to the root of their communication," said Zanna Clay, from the University of Birmingham's School of Psychology.

It is widely assumed that primate calls are assigned to specific emotional states, while humans' vocalizations are free of this. This may be true for adults, but before language develops babies produce a group of calls (called "protophones") that differ from crying and laughter and are independent of their emotional state.

"We felt that it was premature to conclude that this ability is uniquely human, especially as [nobody] had really looked for it in the great apes. It appears that the more we look, the more similarity we find between animals and humans," Clay said.

The peeps observed in the bonobos could represent an evolutionary transition from "functionally fixed animal vocalizations" towards human vocalizations.

The findings were published in a recent edition of the journal PeerJ.