Neandertal vocal tract

Potential speech abilities constitute a key component in the description of the Neandertals and their relations with modern Homo Sapiens. Since Lieberman & Crelin postulated in 1971 the theory that “Neanderthal man did not have the anatomical prerequisites for producing the full range of human speech” their speech capability has been a subject of hot debate for over 30 years, and remains a controversial question.

In this study, we first question the methodology adopted by Lieberman and Crelin, and we point out articulatory and acoustic flaws in the data and the modeling. Then we propose a general articulatory-acoustic framework for testing the acoustic consequences of the trade-off between oral and pharyngeal cavities. Specifically, following Honda & Tiede (1998), we characterize this trade-off by a Laryngeal Height Index (LHI) corresponding to the length ratio of the pharyngeal cavity to the oral cavity. Using an anthropomorphic articulatory model controlled by lips, jaw, tongue and larynx parameters, we can generate the Maximal Vowel Space (MVS), which is a triangle in the F1 / F2 plane, the three point vowels /a/, /i/, and /u/ being located at its three extremities. We sample the evolution of the position of the larynx from birth to adulthood with four different LHI values, and we show that the associated MVS are very similar. Therefore, the MVS of a given vocal tract does not depend on the LHI: gestures of the tongue body, lips and jaw allow compensations for differences in the ratio between the dimensions of the oral cavity and pharynx. We then infer that the vowel space of Neandertals (with high or low larynx) was potentially no smaller than that of a modern human and that Neandertals could produce all the vowels of the world’s languages. Neandertals were no more vocally handicapped than children at birth are. Therefore, there is no reason to believe that the lowering of the larynx and a concomitant increase in pharynx size are necessary evolutionary pre-adaptations for speech. However, since our study is strictly limited to the morphological and acoustic aspects of the vocal tract, we cannot offer any definitive answer to the question of whether Neandertals could produce human speech or not.