Humans are the only species to be able to speak language. This is done by using sounds to create words, and words to make hierarchically-structured sentences. It remains unanswered where this remarkable ability came from. Researchers often employ a comparative approach to help them trace the evolution of human language. They compare vocal productions from other animals to humans to find out. Non-human primates, on the other hand, use single calls (called call types) and rarely combine them to create vocal sequences.
Therefore, non-human primates’ vocal communication seems less complicated than humans. Human language complexity is not due to the amount of sounds we use to communicate, which typically exceeds 50 in most languages. It comes from how we combine sounds to create words and hierarchically combine them to create sentences that can express infinite meanings. Non-human primates can use 38 different sounds to communicate but rarely mix them. We may not be able to fully understand the structure and variety of vocal sequences produced non-human primates because they have not been studied in detail.
Researchers have recorded thousands upon thousands of vocalizations
Researchers from MPI-EVA in Leipzig and MPI–CBS in Bron, France, and the Institute of Cognitive Sciences in Bron at the CNRS, Lyon, France, collected thousands of vocalizations by wild chimpanzees living in the Tai National Park, Ivory Coast. They identified 12 call types and analyzed how chimpanzees use them to create vocal sequences. Cedric Girard – Buttoz, the first author of this study, says that “Observing animals in their natural social and ecological environment reveals a previously undiscovered complexity in the ways they communicate.” Emiliano Zaccarella is another leading author.
This study shows that chimpanzees can communicate with one another using hundreds of different sequences. They also use up to ten call types from the entire repertoire. This is the first time that non-human primates have ever recorded such a wide range of vocal production. The researchers also found that calls, when combined with other calls, were predictable to occur in certain positions within the sequence. This was in accordance with adjacency rules. These adjacency guidelines were also applicable to sequences containing three types of calls.
Tatiana Bortolato, co-author of the study, said that the findings “highlight a vocal communication system in chimpanzees that is much more complex and structured than previously thought”. She recorded the vocalizations in the forest. This is the first study of a larger project. Catherine Crockford, senior researcher on the study, says that by studying the richness of the vocal sequences in wild chimpanzees (a socially complex species as humans), we hope to gain new insight into where we came from and how our unique language evolved.
These complex vocal sequences will be investigated by the authors to determine if they enable chimpanzees increase their communication range.