Evolutionary loss of complexity in human vocal anatomy as an adaptation for speech

• DOI: 10.1126/science.abm1574
• Publication Date: 2022-08-11T17:58:26Z
• Authors: Takeshi Nishimura; Isao T. Tokuda; Shigehiro Miyachi; Jacob C. Dunn; Christian T. Herbst; Kazuyoshi Ishimura; Akihisa Kaneko; Yuki Kinoshita; Hiroki Koda; Jaap P. P. Saers; Hirohiko Imai; Tetsuya Matsuda; Ole Næsbye Larsen; Uwe Jürgens; Hideki Hirabayashi; Shozo Kojima; W. Tecumseh Fitch
• Keywords: Vocal tract; Harmonic; Articulatory Phonetics; Human voice

Human speech production obeys the same acoustic principles as vocal in other animals but has distinctive features: A stable source is filtered by rapidly changing formant frequencies. To understand evolution, we examined a wide range of primates, combining observations phonation with mathematical modeling. We found that stability relies upon simplifications laryngeal anatomy, specifically loss air sacs and membranes. conclude evolutionary membranes allows human to mostly avoid spontaneous nonlinear phenomena chaos common primate vocalizations. This our larynx produce stable, harmonic-rich phonation, ideally highlighting changes convey most phonetic information. Paradoxically, increased complexity spoken language thus followed simplification anatomy.