Speech is a sophisticated biomechanical process, that has taken millennia to evolve. This is something for oromyofunctional-focussed speech-language pathologists to know about. When we talk to our patients of ‘natural’ resting postures or ‘restoring’ functionality, it is this background to which we implicitly refer. Wittingly or not, we use these terms a very holistic sense indeed.
There is now much recent scholarship on how humans used to sound, and how our speech-producing mechanisms have changed over time. A particularly useful study, a multi-university archeo-linguistic investigation of the vocal tract as ‘time machine’, has just appeared (Dediu D, et al., Philos Trans R Soc Lond B Biol Sci. 2021 May 10;376(1824):20200192. doi: 10.1098/rstb.2020.0192) It is a very fine depiction indeed of past speech and language combined with the ever-changing anatomy of the speech organs, a paper very well worth reading for a wider understanding of many present issues in speech-language pathology.
Modelling studies on the extensive variation between individuals in the precise shape of the vocal tract, and its effect on speech and language show, for example, data on the lower jaw and the hard palate, extracted and digitized from the osteological remains of three historical populations from The Netherlands, that allows three-dimensional biomechanical simulations of vowel production. From this it is possible to recover the signatures of inter-individual variation between these vowels, in acoustics and articulation, and draw clear inferences about historic and prehistoric languages. Moreover – and this is of use clinically – it forces us to consider the wider context of language use, including the anatomy, physiology and cognition of all speakers, even ones alive today.
This recent study focusses on only recent historical populations from well-understood contexts (medieval and post-medieval northwestern Europe) for pragmatic reasons (reliable contextual information, good preservation, access to digitization technology, osteological expertise) and theoretical reasons (controversies about sexing using the lower jaw, changes in food and nutrition, sound changes in the history of Dutch). But the data it assembles can be used further back in time, since there are well-preserved components of the vocal tract deep in the fossil record for comparison, preceding the emergence of anatomically modern humans by several hundred thousand years, which is to say deep into the stone age.
Though this study is principally one of vowel production, that includes the formants F1 to F5 and the spectra up to 5000 Hz, a great many inferences can be made about specifics of a variety of sounds, such as the alveolar ridge and its effects on click consonants, hard palate shape and ‘r’, dentition, bite and labiodentals, and larynx position and vowels. There are still languages, in fact, that use alveolar-ridge phonemic clicks. This is something that could be of note in some contemporary clinical settings. Another point of interest is that, from the negative effects of the edge-to-edge bite on labiodentals that we know about in recent hunter-gatherers, we can infer that humans before 12,000 years ago (this includes H. erectus and Neanderthals) did not use ‘f’ and ‘v’ very much. Cavemen wouldn’t have used the word ‘favor’, in other words. From the shape of the mesolithic hard palate we even know something about how they probably would have articulated that ‘r’.
We are still learning about the type and patterning of variation in vocal tract anatomy, physiology, and control in present-day humans, and its effects on speech and language. Forensic work in studies like this one, on hard palate, alveolar ridge, and bite, is invaluable background for our learning. Other research directions could now concern the curvature of the cervical spine and pitch, or the anatomy of the nasal cavity and the velum with respect to vowel nasalization. Our understanding of the complex relationships like these, between vocal tract anatomy, sound change and linguistic diversity, will be of tremendous use as the data fill in.
MyoNews from BreatheWorksTM is a report on trends and developments in oromyofunctional disorder and therapy. These updates are not intended as diagnosis, treatment, cure or prevention of any disease or syndrome.