Chimpanzees use numerous flexible vocal sequences with more than two vocal units: A step towards language?

Abstract

A major question in evolutionary science is how did language evolve? Syntax, as the core of language, combines meaning-bearing units (words) into hierarchical structures, thereby creating new meanings. Some other mammals and birds combine meaning-bearing vocalisations, but no documented examples exist of non-human animals combining more than two meaning-bearing vocalisations. Was the two-unit threshold only surpassed in the hominid lineage? Here, we examine the positional patterning of vocal sequences of chimpanzees. We analysed 4826 vocal utterances of 46 wild adult female and male chimpanzees. We found a flexible system with 390 multi-unit vocal sequences, some showing positional or transitional regularities. Two-unit pairs embedded in three-unit sequences predictably occurred either in head or tail positions, and co-occurred with specific other elements. The capacity to organise vocal output beyond the two-unit level may thus exist in species other than humans and could be viewed as an important evolutionary step towards language.

Chimpanzee vowel-like sounds and voice quality suggest formant space expansion through the hominoid lineage

“…emitted at food), are produced with wider intervals. In order not to artificially increase the number of bouts, we therefore used a one-second rule, as other studies have done [ 25 ]. In order to limit pseudoreplication, we randomly selected a maximum of two non-adjacent BU of the same call type within a call bout for each analysis, and medianized values of both BU in each bout.…”

Comparing human and chimpanzee temporal lobe neuroanatomy reveals modifications to human language hubs beyond the frontotemporal arcuate fasciculus

“…Such results not only demonstrate a much more complex organization of cortical anatomy across species ( 22 ), but they also highlight the phylogenetic origins of presumed human adaptations for language ( 23 ). These recent findings can now be integrated with an increased appreciation of the behavioral abilities of great apes, including sophisticated organization of vocal output ( 24 ).…”

Sequential and network analyses to describe multiple signal use in captive mangabeys

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