Humans are the only species on earth known to use language. We do this by combining sounds to form words and words to form hierarchically structured sentences. The question, where this extraordinary capacity originates from, still remains to be answered. In order to retrace the evolutionary origins of human language, researchers often use a comparative approach — they compare the vocal production of other animals, in particular of primates, to those of humans. In contrast to humans, non-human primates often use single calls -referred to as call types — and rarely combine them with each other to form vocal sequences.
Consequently, vocal communication in non-human primates seems much less complex than human communication. However, human language complexity does not arise from the number of sounds we use when we speak, which is typically bellow 50 different sounds in most languages, but from the way we combine sounds in a structured manner to form words and hierarchically combine these words to form sentences to express an infinite number of meanings. In fact, non-human primates also use up to 38 different calls to communicate, but they rarely combine them with each other. However, since they have so far not been analysed in great detail, we may not have a full picture of the structure and diversity of vocal sequences produced by non-human primates.
Researchers at MPI-EVA and MPI-CBS in Leipzig and from the Institute of Cognitive Sciences at the CNRS in Bron, Lyon, France, recorded thousands of vocalisations produced by the members of three groups of wild chimpanzees in the Taï National Park in Ivory Coast. They identified 12 different call types and assessed how chimpanzees combine them to form vocal sequences. “Observing animals in their natural social and ecological environment reveals a previously undiscovered complexity in the ways they communicate,” says first author Cédric Girard-Buttoz. “Syntax is a hallmark of human language and in order to elucidate the origin of this human ability it is crucial to understand how non-human primate vocalisations are structured,” adds Emiliano Zaccarella, another lead author of the study. [Continue reading…]