Vocal Combinations in the Southern Pied Babbler (Turdoides bicolor) and the Chestnut-Crowned Babbler (Pomatostomus ruficeps): Implications for the Evolution of Human Language

Abstract

Language’s expressive power is one of its key characterising features. This generative capacity is achieved through language’s double articulatory nature: meaningless sounds (phonemes) are combined to create meaningful words (phonology/combinatoriality), and words are assembled into higher-order meaningful phrases (syntax/compositionality). Comparative work on non-human animals investigating the evolutionary origin of combinatorial abilities has so far focused on singing species or on primates. Although these studies have shed light on the combinatorial capacities outside of humans, evidence for basic phoneme-like or semantically compositional structures in non-human communication systems is rare. By taking a comparative approach, investigating the prevalence and diversity of combinatoriality within the discrete call system of two highly social passerine birds, this dissertation aimed to unveil selective drivers promoting combinatorial capacities, and provides analogue examples to, and potential precursors of, language’s combinatorial layers. Work on chestnut-crowned babblers (Pomatostomus ruficeps) demonstrates the reuse of two meaningless sounds (A & B) in different arrangements to generate the functionally distinct A