Vocal fold control beyond the species-specific repertoire in an orang-utan

• Published in: Scientific reports 2016-07, Vol.6 (1), p.30315-30315, Article 30315
• Main Authors: Lameira, Adriano R., Hardus, Madeleine E., Mielke, Alexander, Wich, Serge A., Shumaker, Robert W.
• Format: Article
• Language: English
• Subjects: 631/181/19/2471; 631/181/2468; 631/378/2632/1663; 631/601/18; Animals; Biological Evolution; Humanities and Social Sciences; multidisciplinary; Pongo - genetics; Pongo - physiology; Science; Science (multidisciplinary); Vocal Cords - physiology; Vocalization, Animal
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep30315

Vocal fold control was critical to the evolution of spoken language, much as it today allows us to learn vowel systems. It has, however, never been demonstrated directly in a non-human primate, leading to the suggestion that it evolved in the human lineage after divergence from great apes. Here, we provide the first evidence for real-time, dynamic and interactive vocal fold control in a great ape during an imitation “do-as-I-do” game with a human demonstrator. Notably, the orang-utan subject skilfully produced “wookies” – an idiosyncratic vocalization exhibiting a unique spectral profile among the orang-utan vocal repertoire. The subject instantaneously matched human-produced wookies as they were randomly modulated in pitch, adjusting his voice frequency up or down when the human demonstrator did so, readily generating distinct low vs. high frequency sub-variants. These sub-variants were significantly different from spontaneous ones (not produced in matching trials). Results indicate a latent capacity for vocal fold exercise in a great ape ( i ) in real-time, ( ii ) up and down the frequency spectrum, ( iii ) across a register range beyond the species-repertoire and, ( iv ) in a co-operative turn-taking social setup. Such ancestral capacity likely provided the neuro-behavioural basis of the more fine-tuned vocal fold control that is a human hallmark.