Evolution of the human tongue and emergence of speech biomechanics

Abstract

The tongue is one of the organs most central to human speech. Here, the evolution and species-unique properties of the human tongue is traced, via reference to the apparent articulatory behavior of extant non-human great apes, and fossil findings from early hominids – from a point of view of articulatory phonetics, the science of human speech production. Increased lingual flexibility provided the possibility of mapping of articulatory targets, possibly via exaptation of manual-gestural mapping capacities evident in extant great apes. The emergence of the human-specific tongue, its properties, and morphology were crucial to the evolution of human articulate speech.

What phonetics has to say about Neanderthal (H. Neanderthalensis) speech capacities

“…In speech, the voice "source" from the vocal folds of the larynx is "filtered" in the supralaryngeal vocal tract (SVT) by the imposition of narrow constrictions using the various articulators, including the jaw, lips, velum, palate, and tongue (Fant, 1960). Because essential features of vocal anatomy are largely preserved across mammals, such fundamentals of speech acoustics have served as starting points for literature on the evolution of speech capacities (Negus, 1949;Lieberman et al, 1969Lieberman et al, , 1972de Boer & Fitch, 2010;Fitch et al, 2016;Ekström & Edlund, 2023). The variable most crucial to the extent of the uniquely human range of speech sounds is the shape and position of the tongue inside the SVT, and the shape of the SVT itself (Lieberman et al, 1972;Carré et al, 1995;de Boer, 2010;de Boer & Fitch, 2010).…”

“…Results supported the view that Neanderthals may have been unable to articulate the full range of human speech sounds have since been a focal point in subsequent debate on Neanderthal speech capacities. Crelin (1987) extended the efforts begun by Lieberman and Crelin (1971) to various extinct hominids (see review in Ekström & Edlund, 2023). Also based on the "basicranial" assumption, Crelin determined that skulls of both australopiths and H. habilis were "apelike", while those of H. erectus were intermediate in form.…”

Correcting the record: Phonetic potential of primate vocal tracts and the legacy of Philip Lieberman (1934−2022)

“…Lameira, 2017;Lieberman et al, 1992;. However, speech sounds cannot be treated in isolation; phoneticians have long known that the steady stream of speech is not reducible to individual sounds (e.g., Ekström & Edlund, 2023;Liberman et al, 1967;Lindblom & Sussman, 2012;Öhman, 1967;Peterson et al, 1958;overviews in Hardcastle & Hewlett, 1999): phonemes are executed continuously, and their execution is always affected by neighboring sounds-a phenomenon known as coarticulation. Accordingly, in speech, no one speech sound can be realistically removed from its context.…”

“…The "adult" vocal tract is attained only throughout maturation, with the broader geometric dimensions of adulthood typically emerging sometime after 6 years of age (Fitch & Giedd, 1999;Lieberman, 2012;Lieberman & McCarthy, 1999;Lieberman et al, 2001;Vorperian et al, 2005Vorperian et al, , 2009. The phylogenetic descent of the larynx observable in modern humans is accomplished via shortening of the oral cavity, restructuring of the cranium, partial descent of the larynx and tongue root into the now-expanded pharynx, resulting in a rough 1:1 relationship between horizontal and vertical sections of the vocal tract (Du Brul, 1977;Carré et al, 1995Carré et al, , 2017Ekström & Edlund, 2023;Lieberman, 2011Lieberman, , 2012Lieberman & McCarthy, 1999).…”

A theory that never was: Wrong way to the “Dawn of speech”

“…In human speech production, the voice "source" from the vocal folds of the larynx is "fil tered" in the supralaryngeal vocal tract (SVT) by the imposition of narrow constrictions using the various articulators, including the jaw, lips, velum, palate, and tongue (Fant, 1960), resulting in variations in the resulting resonance frequencies, termed formants. Because essential features of vocal anatomy are largely preserved across mammals, such fundamentals of speech acoustics have served as starting points for literature on the evolution of speech capacities (de Boer & Fitch, 2010;Ekström & Edlund, 2023;Fitch et al, 2016;Lieberman et al, 1969Lieberman et al, , 1972Negus, 1949).…”