While bonobos do not have as many characteristics similar to humans as chimpanzees do, they were observed achieving something previously believed to be human-exclusive.

According to BBC News, authors of a study published in the journal PeerJ observed wild bonobos flexing their vocal chords in a way only seen in humans. The bonobos were able to manipulate a high-pitched call for a variety of purposes akin to how a human baby communicates before learning words.

"Animal vocalizations are usually made in relatively narrow behavioral contexts linked to emotional states, such as to express aggressive motivation or to warn about potential predators," read a press release detailing the new study. "In contrast, humans exhibit 'functional flexibility' when vocalizing in a variety of situations.

"[The researchers] found broad similarity in the acoustic structure across different contexts suggesting contextual flexibility in this call. Similar to human infants, recipients therefore have to make pragmatic inferences about the meaning of this call across contexts."

The study authors referred to the call as a "peep" and reported hearing the bonobos using it in all sorts of situations with positive, negative, and neutral connotations. As humans do, the peep's recipient had to use logic to figure out what its counterpart was referring to.

"It's not easy to get access to these animals in the wild... and this is really important data," Simon Townsend, a University of Zurich animal communication expert not involved with the study, told BBC News. "It goes along with a growing body of evidence that suggests that primates do have quite a bit of control... and goes against the general idea that animals are somehow constrained by their emotional state."