London, Aug 5 (IANS) Just as humans babies can produce vocalisations in a wide range of emotional states and situations, wild bonobos, our closest living relatives, use a single high-pitched call in a variety of contexts, new research has found.
The findings suggest that this flexibility in vocalisation – an ability thought essential for development of language – may not be uniquely human and that the core features of human language have deep roots in the primate lineage.
“The more we look, the more continuity we find among animals and humans,” said one of the study authors Zanna Clay from University of Birmingham in England.
Animal vocalisations 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.
But the new study conducted on wild bonobos found that in this species individuals produce a call type, known as the ‘peep’, across a range of positive, negative and neutral situations, such as during feeding, travel, rest, aggression, alarm, nesting and grooming.
Peeps are high-pitched vocalisations which are short in duration and produced with a closed mouth.
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 evolutionary transition from functionally fixed animal vocalisations towards flexible human vocalisations seems to have appeared some 6-10 million years ago in the shared common ancestor between humans and great apes, said the study published in the journal PeerJ.