Wild bonobos produce human child-like vocalisations

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Researchers have found that wild bonobos – our closest living relatives – are able to produce vocolisations similar to human infants and this finding, they say, could be a link that will help them decode the evolutionary transition from functionally fixed animal vocalisations towards flexible human vocalisations.

Human infants vocalise from an early age and produce sounds in a wide range of emotional states and situations – something that researchers have long thought of as one of the requirements for the development of language.

Researchers say that animal vocalisations are are usually made in relatively narrow behavioural contexts linked to emotional states, such as to express aggressive motivation or to warn about potential predators. In contrast, humans exhibit ‘functional flexibility’ when vocalizing in a variety of situations.

An international team of researchers from University of Birmingham, UK and the University of Neuchatel, Switzerland carried out research on wild bonobos and found that individuals in this species produce a call type, known as the ‘peep’ – high-pitched vocalisations which are short in duration and produced with a closed mouth..

Researchers found that bonobos produce these ‘peep’ across a range of positive, negative and neutral situations, such as during feeding, travel, rest, aggression, alarm, nesting and grooming. 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.

Author Zanna Clay said that the findings show that “more research needs to be done on our great ape relatives before we can make conclusions about human uniqueness. The more we look, the more continuity we find among animals and humans”

The type of functional flexibility they observed in bonobos could represent an important evolutionary transition from functionally fixed animal vocalisations towards flexible human vocalisations, which seems to have appeared some 6-10 million years ago in the shared common ancestor between humans and great apes. It appears that many of the core features of human language have deep roots in the primate lineage.