BIRMINGHAM, England, Aug. 4 (UPI) -- The speech patterns of wild bonobos, mankind's closest living relative, resemble human baby talk. The apes used high-pitched "peeps," similar to those employed by human infants.
Peeps, short and high-pitched, are produced with a closed mouth, and serve a range of scenarios -- good, bad and neutral. Though the sound of these calls don't change, the different contexts alter the meaning.
Previously, researchers believed different ape calls to be tied closely to unique emotional circumstances. Human language was thought to be categorically different, with vocalizations free to be used across varying circumstances.
But the new findings undermine this distinction.
"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," Zanna Clay, a researcher and professor at the University of Birmingham's School of Psychology, said in a press release. "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."
Clay, who led the field research, is also lead author of a new paper on the discovery, published this week in the journal PeerJ.
The work of Clay and her colleagues prove that bonobos, like babies, have unanchored calls -- independent of positive or negative vocalizations (laughing and crying, in an infant's case). Clay says these calls are evidence of an evolutionary transition between animal and human language.
"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," she said. "It appears that the more we look the more similarity we find between animals and humans."