The vocal tract as a time machine: inferences about past speech and language from the anatomy of the speech organs

Abstract

While speech and language do not fossilize, they still leave traces that can be extracted and interpreted. Here, we suggest that the shape of the hard structures of the vocal tract may also allow inferences about the speech of long-gone humans. These build on recent experimental and modelling studies, showing that there is extensive variation between individuals in the precise shape of the vocal tract, and that this variation affects speech and language. In particular, we show that detailed anatomical information concerning two components of the vocal tract (the lower jaw and the hard palate) can be extracted and digitized from the osteological remains of three historical populations from The Netherlands, and can be used to conduct three-dimensional biomechanical simulations of vowel production. We could recover the signatures of inter-individual variation between these vowels, in acoustics and articulation. While ‘proof-of-concept’, this study suggests that older and less well-preserved remains could be used to draw inferences about historic and prehistoric languages. Moreover, it forces us to clarify the meaning and use of the uniformitarian principle in linguistics, and to consider the wider context of language use, including the anatomy, physiology and cognition of the speakers.
This article is part of the theme issue ‘Reconstructing prehistoric languages’.

Full text

royalsocietypublishing.org/journal/rstb
Research
Cite this article: Dediu D, Moisik SR, Baetsen
WA, Bosman AM, Waters-Rist AL. 2021 The
vocal tract as a time machine: inferences about
past speech and language from the anatomy
of the speech organs. Phil. Trans. R. Soc. B
376: 20200192.
https://doi.org/10.1098/rstb.2020.0192
Accepted: 5 November 2020
One contribution of 17 to a theme issue
‘Reconstructing prehistoric languages’.
Subject Areas:
cognition
Keywords:
vocal tract, phonetics, osteology,
language change
Author for correspondence:
Dan Dediu
e-mail: dan.dediu@univ-lyon2.fr
Electronic supplementary material is available
online at https://doi.org/10.6084/m9.figshare.
c.5336618.
The vocal tract as a time machine:
inferences about past speech and
language from the anatomy of the
speech organs
Dan Dediu1, Scott R. Moisik2, W. A. Baetsen3, Abel Marinus Bosman4,5
and Andrea L. Waters-Rist6
1
Laboratoire Dynamique De Langage (DDL) UMR 5596, Université Lumière Lyon 2, Lyon, France
2
Division of Linguistics and Multilingual Studies, Nanyang Technological University, Singapore, Republic of
Singapore
3
RAAP Archeologisch Adviesbureau b.v., Leiden, The Netherlands
4
DFG Center for Advanced Studies ‘Words, Bones, Genes, Tools: Tracking Linguistic, Cultural, and Biological
Trajectories of the Human Past’, Eberhard Karls Universität Tübingen, Tübingen, Baden-Württemberg, Germany
5
IDDS Groep b.v., Noordwijk, The Netherlands
6
Department of Anthropology, The University of Western Ontario, London, Canada
DD, 0000-0002-0704-6365
While speech and language do not fossilize, they still leave traces that can
be extracted and interpreted. Here, we suggest that the shape of the hard
structures of the vocal tract may also allow inferences about the speech of
long-gone humans. These build on recent experimental and modelling
studies, showing that there is extensive variation between individuals in
the precise shape of the vocal tract, and that this variation affects speech
and language. In particular, we show that detailed anatomical information
concerning two components of the vocal tract (the lower jaw and the hard
palate) can be extracted and digitized from the osteological remains of
three historical populations from The Netherlands, and can be used to con-
duct three-dimensional biomechanical simulations of vowel production.
We could recover the signatures of inter-individual variation between
these vowels, in acoustics and articulation. While ‘proof-of-concept’, this
study suggests that older and less well-preserved remains could be used
to draw inferences about historic and prehistoric languages. Moreover, it
forces us to clarify the meaning and use of the uniformitarian principle in
linguistics, and to consider the wider context of language use, including
the anatomy, physiology and cognition of the speakers.
This article is part of the theme issue ‘Reconstructing prehistoric
languages’.
1. Introduction
Obviously, the dead cannot speak: we cannot listen to Shakespeare reading
A Midsummer Night’s Dream, we cannot elicit verb conjugations from Cicero,
and we cannot even get Tutankhamun to say ‘aaah’…The furthest we could
get—which is incontestably a tour de force—was to CT-scan the mummified
body of an Egyptian scribe and priest, Nesyamun, from about 3000 years
ago, print a three-dimensional reconstruction of his vocal tract, and produce
a creepy sounding [æ:::] [1]. That, and the various attempts to simulate Nean-
derthal vowels based on debatable reconstructions and assumptions, leading
to endless debates about their capacity (or lack thereof) to articulate the ‘full
modern’vowel space, with a particular focus on [u] [2–6]. While we are far
from a general consensus, language and speech go back at least to the origins
© 2021 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution
License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original
author and source are credited.

of modern humans a few hundred thousands of years ago
[7,8] but, most probably (given recent evidence), at least to
the last common ancestor of modern humans and our closest
evolutionary relatives, the Neanderthals and the Denisovans,
about half a million years ago [9,10].
But our limits in what concerns the speech andlanguage of
long-gone people run deeper than this: there seems to a wide-
spread assumption in linguistics that, on the one hand, there
are precious few traces left by speech and language (writing
goes back not more than a few thousand years) and, on the
other, living (and attested) languages are very poor at retaining
information about their earlier stages. Taken together, these
seem to impose a ‘time horizon’beyond which we cannot
really know much [11], a time horizon that is usually placed
at most 10000 years ago, and rooted in the breakdown of the
‘standard’historical linguistic comparative method of infor-
mation recovery and inference ([12–15]; see also [16]). This
breakdown results in the reluctance to connect established
language families into larger (and, presumably, deeper) con-
structs such as ‘Nostratic’[17,18], ‘Eurasiatic’[19] or ‘Altaic’/
’Transeurasian’[20,21]. While this reluctance is clearly justified
[11,17,22] by the daunting methodological and data avail-
ability issues, which make it very hard to distinguish biases
and a priori stances from actual inferences from the data, it
also makes it very hard to study these issues.
Nevertheless, there are intriguing hints that language might
not be as bad at retaining information afterall, especially when
combined with external sources of evidence, such as (ancient)
genetics [23–25] and archaeology [26], but accessing it requires
the development and application of new methods, cross-disci-
plinary collaborations and, most importantly, the willingness
to accept that false positives will inevitably be generated, but
that the scientific process will weed (most of) them out. In
this context, it is interesting to note that quantitative methods
borrowed from evolutionary biology (especially Bayesian phy-
logenetics) have not only helped refine the internal structure of
established language families (such as Indo-European, Austro-
nesian, Uralic or Pama-Nyungan), but also, especially
combined with external evidence, suggested ideas about their
origins and spread [27–30], pushing the boundaries to 5000–
8000 years ago. The same class of methods, however, has been
used to explore even ‘deeper’connections between languages,
producing exciting but highly controversial results. Some of
these results include: the apparent support for something
akin to Eurasiatic (about 15 000 years ago) from phylogenetic
methods applied to cognacy judgments [31] and to the align-
ments of actual Automated Similarity Judgment Program
(ASJP; [32]) transcriptions [33]; the proposed Bayesian phyloge-
netic evidence for Transeurasian [20]; the very indirect finding
that the stability of structural features of language might con-
serve continent-wide deep signals of shared ancestry and/or
contact, suggesting connections between the language families
of the Americas and north-eastern Eurasia going back approxi-
mately 15 000 years or so [34]; and, the bold claim that
phonological systems might retain a signal of the modern
human expansion from Africa some tens of thousands of
years ago [35,36]. However, besides being currently unclear
how reliable these findings are [22,37,38], they only push our
knowledge back but a sliver of the half million years or so of
human speech and language [9,10], and remain, in general,
fairly abstract and ‘high level’. Can we do better?
Here we suggest that we might be able to infer fairly con-
crete information about past phonetics and phonologies,
going back as far as the fossil record of the Neanderthals
and other ‘archaic humans’(half a million—or even more—
years ago). To do so, we will use the links between aspects
of the vocal tract anatomy, and the articulation and acoustics
of speech which are uncovered by recent investigations into
the patterns of inter-individual variation in the anatomy of
the speech organs. Besides allowing us to make informed
guesses about Neanderthals lacking labiodentals and the per-
sistence of clicks in sub-equatorial Africa, this approach also
questions the indiscriminate application of a strong uniformi-
tarian principle to speech and language, arguing instead for a
much more nuanced inferential framework that takes into
account the wider context of language, which includes,
among others, the physical environment and human biology
[39,40].
2. Variation everywhere
Due to space constraints and the specific focus of this paper,
we will only briefly summarize here points discussed at
length in other publications (e.g. [39–41]). Recent advances
in several scientific fields (including medicine, human
genetics, anthropology and psychology), the availability of
large computer-readable databases, the democratization
of computing power, data analysis and statistics, and wider
changes in how society at large, and science in particular,
sees variation, have allowed a renewed interest in under-
standing how people vary, how this inter-individual
variation is patterned, and how it relates to universal charac-
teristics. What we realize is that, on a massive foundation of
sharedness, individuals vary in subtle ways at all levels of
study: from the molecular [42,43], to the anatomical and
physiological [44], and to the psychological and cognitive
[45]. This variation is mostly small and quantitative, and
results in a wide range of ‘normality’that grades into the
‘pathological’—here we are interested in this normal range
of variation, which is not distributed at random between indi-
viduals, but is intricately patterned. Thus, on the one hand,
any given individual belongs to multiple (overlapping or
nested) groups, and groups differ in myriad continuous,
statistical and multivariate ways (as opposed to ‘crisp’, deter-
ministic, categorical differences driven by one or a few
characteristics, as usually claimed by racist ideologies). This
patterning is rooted in our complex but relatively recent evol-
utionary and demographic history [46–48]: while we are
much more uniform than other species ( for example, there
is less genetic diversity in the 8 billion people spread across
the world than in a few hundred highly geographically
circumscribed chimpanzees; [49]), we do vary, with most of
this variation distributed between individuals (approx.
80%), and not between groups either within (approx. 10%)
or between continents (approx. 10%) [46,50]. Yet, this vari-
ation is informative enough (especially when aggregated
among many genetic loci and characteristics) to recover indi-
vidual origins, geographic patterns of human dispersals and
migrations, and past demographic events [48,51]. This vari-
ation decreases with distance from Africa, is distributed as
continuous and overlapping gradients across many variables,
with very few (if any) sharp boundaries—often referred to as
‘clinal variation’[46,47,52]. Clinal variation underscores the
unity of humankind, and a proper understanding of its pat-
terns and processes represents one of the most powerful
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2

scientific arguments against racism, sexism and other forms
of discrimination [48,53–56].
Language in general, and the vocal tract in particular, are
far from being exceptions, despite decades of focusing on
(absolute) universals and denying, or, at best, dismissing
and trivializing variation as mere irrelevant ‘noise’to be
removed from the analysis and ignored from theorizing. Of
course, this was not a blanket stance, with aspects of vari-
ation being actively studied in, for example, dialectology
[57], sociolinguistics [58] and phonetics [59–64], but it did
result in the marginalization of such inquiries and limited
the appreciation of how widespread variation is, and of
how powerful an explanatory factor it may be [39,41]. How-
ever, focusing on phonetics and phonology alone, the last two
decades have witnessed the accumulation of data concerning
the type and patterns of inter-individual variation in the pro-
duction and perception of speech, as well as a heightened
interest in the theoretical implications for phonology, sound
change and typological diversity [41,65].
Of particular interest here is variation in the anatomy
of the vocal tract structures, especially in those structures that
(i) have a higher chance of preservation in the osteological
and fossil record, or (ii) whose particularities can be inferred
from ancient DNA, and their effects on phonetics and
phonology. While our understanding of the genetic and devel-
opmental underpinnings of the vocal tract is still in its infancy,
being primarily based on pathologies with a genetic component
(see, for example, the information available in OMIM,https://
omim.org/), there are several candidate genes and mechanisms
known, especially concerning the teeth [66,67] and the hard
palate [68,69], but also the skull and the face in general (see,
for example, FaceBase; https://www.facebase.org/). These
sources of information are rich enough to even allow some
inferences about the evolution of the position of the larynx
and the structure of the face from methylation patterns
in ancient DNA extracted from archaic human fossils [70].
However, we are far from being able to reliably reconstruct
the details of normal variation in vocal tract anatomy from
the (epi)genetic variants ascertained from the remains of a
given individual, which means that, at least for now, we
should focus instead on the osteological and fossil record,
which has the advantage that the relevant anatomical details
are sometimes preserved well enough, but is affected by the
twin disadvantages of very small (and geographically
and historically skewed) sample sizes, and the lack of soft
tissue preservation (with a few notable exceptions involving
special taphonomic conditions such as anaerobic bogs, perma-
frost or ice; [71,72]). It is also important to recognize the
potential influence of environmental factors on the physiology
and anatomy of the vocal tract. The desiccation of the vocal
folds, and its subsequent phonatory consequences, in environ-
ments with low air humidity [73,74] is an example of the first
type, while the sexually dimorphic and geographically patter-
ned variation in the nasal cavity [75–77], which seems
partly explained by the need to warm and humidify the
in-breathed air in cold and dry climates [76,78–80], with
possible consequences for nasalization, is an example of the
second type.
Before discussing the type of vocal tract data that can be
recovered from this record, and the kind of inferences for
speech and language that can be made, we briefly review
a few studies linking variation in details of vocal tract
anatomy to phonetics and phonology using a multitude of
methodologies, including experimental designs with living
people, computational modelling and phylogenetic inferences.
3. From details of the vocal tract to phonetic
and phonological diversity
To begin, there are well-known claims that the position of
the larynx within the throat can be inferred from traces in the
archaeological record, most notably the shape of the base of
the cranium and characteristics of the hyoid bone, and that
this positioning might allow us to say something about the
capacity of ancient humans to produce (or not) the full
modern vowel space [2,3,5,6,9]. However, despite claims to
the contrary [81,82], it is far from clear how reliable such
reconstructions are (even when adding inferences from ancient
epigenomes; [70]), but, more importantly, it is not obvious what
articulatory, acoustic and linguistic effects different positions
of the larynx would have. The original claims [6] that
Neanderthals had a much higher larynx than modern
humans and that this precluded them from producing the full
spectrum of vowels found in the currently spoken languages,
did not age well. Newer models of speech articulation seem
to suggest that the vowel space produced with a higher
larynx is not terribly limited thanks to active compensation by
the other articulators [2–4], that the rest position of the larynx
is not very relevant given its wide dynamic range [83,84], and
that the Neanderthal hyoid bone was, in fact, anatomically
and biomechanically extremely similar to the modern human
one [85]. Finally, despite the importance of the peripheral
vowels, and the fact that actual speech productions are spread
across the potential (acoustic and articulatory) vowel space rela-
tively independently of the described phonological system of
the language, few modern languages use the full extent of
this potential space to convey phonological distinctions.
As we will detail below, the hard structures of the vocal
tract have by far the highest chances of preservation in the
osteological and fossil record, suggesting that we should
focus on the hard palate, the jaw and the teeth. There is tre-
mendous inter-individual morphological variation in all
these structures, and some aspects of this variation are pat-
terned, in a continuous, statistical and multivariate manner,
also between groups [39,41]. We will briefly review a few
studies, using a variety of methods and data, showing how
normal variation in these structures affects speech.
There are experimental indications that the midsagittal
shape of the hard palate—between ‘domed’and ‘flat’—influ-
ences token-to-token variability, with speakers with ‘flatter’
palates showing less articulatory variability [61,86]. Compu-
ter models combining a realistic geometric model of the
vocal tract (VocalTractLab 2.1; https://www.vocaltractlab.
de/; [87]) controlled by a neural network, which repeatedly
learns and transmits vowels across multiple generations
[88], show that details of the midsagittal shape of the hard
palate, as quantified using Bézier curves [89], do affect the
articulation and acoustic properties of vowels. Importantly,
the acoustic effects survive the active compensation by the
free articulators (the tongue, jaw and lips) and, despite
being very weak in any particular generation, are amplified
by repeated learning across generations, to the level of the
acoustic variation observed within actual languages [88].
Zooming in on a specific substructure of the hard palate, the
alveolar ridge (a shelf-like structure behind the upper incisors),
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3

biomechanical models using ArtiSynth [90] show that its shape
and size affect the effort required for the articulation of click
consonants as well as their acoustic properties [91]. Specifically,
the alveolar ridge shape that is statistically most often found
among the native speakers of ‘click languages’in southern
Africa (i.e. a ‘small’or ‘absent’alveolar ridge) seems to reduce
the effort needed and may simultaneously enhance the acous-
tics of clicks. There is also experimental evidence from a
large, ethnically diverse sample, using structural, sustained
articulation and real-time magnetic resonance imaging (MRI),
complemented with intra-oral optical three-dimensional
scans and acoustic recordings [41], showing that the strategy
used to articulate the North American English ‘r’is influenced
by the anatomy of the anterior vocal tract, including the hard
palate, the alveolar ridge and the lower jaw. While practically
indistinguishable from an acoustic point of view, these different
articulations nevertheless influence the articulation and acous-
tics of other neighbouring sounds [92,93], thus potentially
influencing sound change.
The last study to be mentioned here [94] combines
biomechanical modelling, large-scale cross-linguistic statistical
analyses, detailed case studies, and Bayesian phylogene-
tic analyses of the Indo-European family. It shows that the
type of bite (‘overjet’/’overbite’versus ‘edge-to-edge’) most
common in a population influences the probability that the
language(s) spoken by that population will have labiodental
sounds (such as ‘f’and ‘v’) in their sound system. Importantly
for us here, the type of bite is strongly influenced by
post-developmental factors, especially the diet, with hunter-
gatherer populations predominantly showing an ‘edge-to-
edge’bite, while those practicing agriculture predominantly
having ‘overjet’/’overbite’[94]. This influence is mediated
by at least two processes having to do with the mechanical
properties of food: tougher foods promote tooth erosion and
movement [95–97], but also affect the growth of the lower
jaw [98].
Taken together (see [39,41] for more comprehensive
reviews and discussions), these studies suggest that (a) there
is extensive normal inter-individual and, in some cases, even
between-group variation in the hard structures of the vocal
tract (e.g. hard palate, teeth, lower jaw); (b) this variation is
mostly continuous, statistical and gradient in nature, but it
(c) sometimes does influence the articulation and/or the acous-
tics of speech sounds, producing (d) (usually very) weak effects
at the individual level (so-called ‘biases’) that nevertheless can
be (e) amplified by the repeated use and transmission of
language to result in unmistakable differences between dialects
and languages in their phonetics and phonology. While this
causal chain is very complex, influenced by many other factors
(e.g. linguistic, cultural, historical, demographic, environ-
mental) and composed of individually subtle links, it does
seem to work, at least in some cases. This raises the hope that
we may be able to infer something about past languages by
combining such findings with information about vocal tract
structures preserved in the osteological and fossil record—to
which we now turn.
4. Aspects of the vocal tract that can be recovered
from the osteological and fossil record
In what concerns the osteological and fossil traces of speech and
language, a lot of attention has been given to the hyoid bone,
the ear structures housed in the temporal bone, the openings
in bones through which nerves can pass (i.e. foramina,
canals), and to endocasts (fossilized brain traces). To date, we
have fossilized hyoids from australopithecines [99], Homo
heidelbergensis and Neanderthals ([85,100,101]; the finding
originally identified as a Homo erectus hyoid[102] has been rein-
terpreted as a fragment of a vertebra [103]), and it seems that,
while the Australopithecus hyoid is clearly different from the
modern human one, the Neanderthal and pre-Neanderthal
ones are very similar to our own [9,104]. The shape of the ear
structures can be reconstructed using computed tomography
(CT) scans, and ear ossicles are sometimes directly preserved
[105–108], allowing inferences about the audition of long-
gone humans: from these, it seems that, functionally, the
hearing of Neanderthals was very similar to that of modern
humans and clearly different from that of chimpanzees [9,10].
Unfortunately, brain endocasts [109,110] and the size of the
hypoglossal canal [111,112] seem to currently offer rather
limited and unclear evidence concerning speech and language.
However, the evidence briefly reviewed above seems to
suggest that we might want toalso focus on other components
of the vocal tract, particularly on those with a bony com-
ponent, increasing their chances of surviving the
taphonomic processes. Evidence suggests that while the
hard palate is a rather fragile structure, it is often quite com-
plete when the cranium is not too fragmented, while the
lower jaw survives rather well [113,114]. In fact, in order to
test the feasibility of extracting information about the hard
palate and the lower jaw from osteological remains, in 2015–
2016 we conducted an exploratory study of well-understood
collections of historic human skeletons (coming from different
cemeteries). The overarching goals were to (a) digitize the
structures of interest in order to (b) compare the historical
samples to each other and with a modern sample, so that we
can (c) ascertain the feasibility of the methods, (d) draw con-
clusions about temporal changes in vocal tract anatomy and,
possibly, (e) their effects on speech and language. The project
was a collaboration between D Dediu and SR Moisik (then
at the Max Planck Institute for Psycholinguistics in Nijmegen,
The Netherlands) and AL Waters-Rist, WA Baetsen and AM
Bosman (then at the Laboratory for Human Osteoarchaeology,
Faculty of Archaeology, Leiden University, also in The Nether-
lands), as part of the larger G[ɜ]bils (Genetic biases in language
and speech) project, funded by The Dutch Research Council
(NWO). Following a careful assessment, considering data
availability, quality, sample size and meta-information, we
decided to use one contemporary and three historical samples,
all collected in The Netherlands (figure 1): Alkmaar (1484–1574
CE), Klaaskinderkerke (thirteenth to sixteenth centuries CE),
Middenbeemster (1829–1866 CE), and part of the contemporary
ArtiVarK sample (2014–2015).
Alkmaar (Paardenmarkt) is the oldest sample; it was part
of a monastic cemetery in present-day Alkmaar in Noord
Holland, in use between 1484 and 1574 CE. Klaaskinderkerke
is a cemetery belonging to a verdronken dorp (lit. ‘drowned vil-
lage’,or‘sunken village’) on the island of Schouwen-
Duiveland in the province of Zeeland, the remains there
dating between the thirteenth and sixteenth centuries CE.
Middenbeemster is a Protestant church cemetery in Noord Hol-
land, located on a polder (or reclaimed lake), the Beemster,
the first in The Netherlands to be dried by building dykes
and pumping out the water using windmills; the remains
are firmly dated between 1829 and 1866 CE. For more
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4

information about these historical samples, see previous
work [115–117]. Finally, the ArtiVarK sample was collected
between 2014 and 2015 in Nijmegen, and contains, of rel-
evance here (see [41] for details), structural MRI and intra-
oral three-dimensional optical scans of approximately 90 par-
ticipants; for this study we used a subset of 34 (16 male; 18
female) contemporary Dutch individuals coming from
across the whole country. See electronic supplementary
material, table S1 for the list of included individuals.
For the hard palate (see [115] for details), we included
22 individuals from the Klaaskinderkerke sample (6 male,
11 probable male, and 5 probable female; 2 young adults,
6 young-middle adults, 10 middle and 4 middle-old
adults—see below for details about the age categories), and
38 individuals from the Middenbeemster sample (17 male,
2 probable male, 3 probable female and 16 female; 22 young
adults and 16 middle adults). For the lower jaw (see [116]
for details), we included 37 individuals from the Alkmaar
sample (6 male, 8 probable male, 5 female and 18 probable
female; 20 young adults and 17 middle adults), and 51 individ-
uals from the Middenbeemster sample (18 male, 10 probable
male, 11 female and 12 probable female; 31 young adults
and 20 middle adults). Note that the estimation of sex and
age-at-death from osteological remains are methodologically
complex, often difficult to perform due to damage resulting
from taphonomy, and their results must be taken as broad
probability estimates [118–120]. Therefore, we decided to
split our individuals (all adults) into two broad groups:
‘young adults’(roughly 18–35 years old at death) and
‘middle adults’(roughly 36–60 years old at death); note that
the age ranges for the Klaaskinderkerke sample carry a greater
uncertainty than the other collections, because of a general
lack of postcranial remains. Likewise, we assign sex with
certainty (male or female) whenever possible, but we also
classified some individuals as ‘probably’of one sex or the
other. Note that, for the Klaaskinderkerke sample, a second,
Figure 1. The map of The Netherlands showing the locations of the four samples (yellow triangles) as well as the location of Amsterdam (red diamond) for
orientation. ArtiVarK is shown as located in Nijmegen. Map generated using QGIS, version 3.10.3-A Coruña.
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5

independent assignment of sex agrees with our own for
all specimens except one (not used in the simulations
conducted here).
The data acquisition and processing protocol was similar
for the two structures: following a general osteological
analysis, meta-data registration, and the application of
various inclusion and exclusion criteria ( good or excellent
preservation, completeness, adult age, the absence of severe
pathologies and abnormalities, and the absence of periodon-
tal disease and ante-mortem tooth loss), the selected
individuals were assessed for sex and their age-at-death
was estimated. Next, the relevant structures were digitized
using a NextEngine™3D Desktop Scanner Ultra HD 2020i
(NextEngine, Inc., Santa Monica, CA), which is widely used
in physical anthropology, palaeoanthropology and other
fields. This device allows the acquisition of high-quality,
high-resolution three-dimensional models of solid objects
using multiple laser beams (for details, see [115,116]). This
resulted in a set of three-dimensional meshes (post-processed
in ScanStudio™and MeshLab; [121]), one per individual and
structure, on which landmarks (fixed, anatomically clearly
defined features that are homologous between individuals)
and semilandmarks (or ‘sliding landmarks’, i.e. a set of vari-
able or ‘mobile’points used to discretize a curve) were placed
using Landmark Editor [122]: there are 27 landmarks for the
lower jaw in the historical samples, 6 in the contemporaneous
ArtiVarK sample (a subset of the 27, due to differing method-
ologies), and 44 for the hard palate (see electronic
supplementary material, tables S2–S5 for a full list including
the sliding semilandmarks; [115], tables 8 and 9, and figure
31 and [117], tables 2 and 3 for details; and electronic sup-
plementary material, figure S8 for their placement). These
allowed us to quantitatively compare the samples and indi-
viduals using classic and geometric morphometric [123]
methods which allow the principled separation of variation
in shape from variation in size.
In a nutshell (see [115] for full details), for the shape of the
hard palate we found that our samples showed a large over-
lap: the variation within both samples is greater than that
between them. This is to be expected, since the populations
were not significantly separated temporally, geographically
or linguistically (Middle Dutch versus modern Dutch; see
[115,124–127]). The small amount of variation we found is
best characterized by subtle differences in the height and
shape (‘U’-shaped versus ‘V’-shaped) of the maxillary
dental arch, as well as the flexion of the basicranial angle,
the relative width of the nasal aperture and the degree of
orthognathy. The only significant difference in average
shape was found between the male group from Klaaskinder-
kerke and the female group from Middenbeemster. Size
differences were found to be statistically significant between
the two samples, with Klaaskinderkerke being slightly larger
than Middenbeemster. The causes for these differences prob-
ably stem from developments during the respective periods
when these people lived, ranging from climatic (temperatures
during the Little Ice Age) to sociocultural (Industrial Revolu-
tion). For the lower jaw (see [116,117] for details), we found
that differences between the two historic samples (Alkmaar
and Middenbeemster) were dominated by size, with the male
individuals from the older site (Alkmaar) having the largest
mandibles on average, and the female individuals from
Middenbeemster having the smallest mandibles. Moreover,
the magnitude of sexual dimorphism seems to differ between
the two sites, with a lower amount of sexual dimorphism pre-
sent in the Alkmaar sample. The results are possibly linked to
a softening of the diet that occurred between these time
periods, although confounding factors such as sampling
bias, life history, and shared population history could not
be accurately accounted for.
There are several methods of palaeodietary reconstruction:
while the faunal and floral remains at an archaeological site
indicate the available foods, the analysis of various aspects of
human bones and teeth indicate what people actually ate.
The stable isotope ratios in bones and teeth paint a broad pic-
ture of the types of plants (C3 versus C4 photosynthetic
pathway) and animals (herbivores versus carnivores, marine
versus terrestrial) that were consumed [128], while dental
calculus often contains masticated food debris, plant microfos-
sils, protein biomolecules, and plant and animal DNA
[129,130]. Such research has been successfully applied to both
recent and ancient remains, including Neandertals and early
modern humans [131,132], and may provide information
about dietary variables that affect vocal tract anatomy. The
macro- and microscopic analysis of dental wear can be useful
for inferring how ‘hard’or ‘soft’the diet was [133,134]. Several
of these methods have been applied to the three historical
samples used here [135–137], but more research and better
data integration are needed before we can study if (and how)
dietary differences might have affected vocal tract anatomy.
With the currently available data, it seems there were no
major differences in dietary ‘softness’among the archaeologi-
cal populations, nor the modern ArtiVarK sample, suggesting
that all groups had diets requiring broadly similar masticatory
forces (but we cannot rule out that this is an artifact of the poor
landmark coverage in the modern sample), concordant to
the historical peasant staples of wheat or rye bread, dairy pro-
ducts (cheese, butter and milk), root vegetables, with smaller
amounts of fish, and even more so, meat.
While still preliminary, these findings do show that (i) we
can recover and quantitatively analyse data pertaining to the
vocal tract from relatively old human remains, and (ii) that
there are quantifiable differences between individuals, locations
and historical periods that may be relevant for speech.
5. Getting the past to ‘speak’: simulating the
articulation of vowels using medieval hard
palates
Here we push this research programme an inch further, by
making a subset of medieval hard palate samples ‘speak’.
More precisely (figure 2; full details about the methods and
results are available in the electronic supplementary materials
‘Modelling the biomechanics and acoustics of reconstructed
vocal tracts: methods and full results’, figures S1–S7 and
Videos), we selected four individuals (two males, one prob-
able male, one probable female; one young-middle adult,
two middle adults, one middle-old adult) for which very
complete skeletal geometry is available, and we used a bio-
mechanical model of the vocal tract (ArtiSynth; [90]) to
reconstruct, as accurately as possible, the way these individ-
uals would have articulated the six vowels [i] (as in the
North American English ‘heat’), [e] (as in ‘hate’), [æ] (as in
‘hat’), [ɑ] (as in ‘hot’), [o] (as in ‘hotel’) and [u] (as in ‘hoot’;
figure 2; electronic supplementary material, figure S2 and
royalsocietypublishing.org/journal/rstb Phil. Trans. R. Soc. B 376: 20200192
6

Videos). What we found is that there are differences in the
acoustics of the vowels between these individuals (electronic
supplementary material, figures S4–S7), some of them rather
dramatic (one case being that the vowel [e] of one individual
is acoustically close to the [i] of the others). While our models
are rather simplistic and, crucially, do not implement articu-
latory compensation or acoustic-auditory-based targeting,
the differences we found are real in the sense that they
would exist in the speech output of these individuals if
they could maintain exactly the same articulatory structure
and posture (given their individual hard palate and denti-
tion); they are components of our organic voice quality
[138,139]. Thus, the individuals must overcome these poten-
tial acoustic differences in their speech, through articulatory
compensation, in order to achieve reasonably well the
intended auditory vowel targets or risk being misunderstood.
Our own previous work [88], using a different type of
model of the vocal tract that does allow for articulatory com-
pensation of differences in the midsagittal shape of the hard
palate through the use of the free articulators (mainly the
tongue, the lips and the lower jaw), shows that even if this
compensation is highly effective, it nevertheless fails to com-
pletely erase the acoustic ‘signature’of inter-individual
anatomical variation. This ‘attenuated’acoustic signature is
very small but present and, perhaps surprisingly, is some-
times amplified by the repeated use and transmission of
language in populations composed of individuals with a
similar anatomy [39,88,91].
All in all, we hope to have shown that (i) information
about vocal tract structures can be successfully extracted
from the remains of long-gone people, (ii) that it can be
used in qualitative, quantitative and modelling investiga-
tions into (iii) the patterning of inter-individual (and,
possibly, inter-group) variation with (iv) consequences for
speech and language.
6. Discussion and conclusion
While the aforementioned data have only ‘scratched the sur-
face’, we do hope to have shown that there is huge potential
in such an approach, which uses traces of vocal tract anatomy
from past people, combined with results from computer
models and experiments in contemporaneous individuals,
to make informed inferences about long-gone languages.
What we have tried to show here concretely is that there is
a wealth of information about specific ‘hard’components of
the vocal tract (the lower jaw and the hard palate) in the
osteological record, that this information can be extracted
and quantified in a rigorous manner, and that it can be
used not only to compare individuals and groups across
time, but also to simulate how these would have affected
the production of vowels. Naturally, these first steps can be
extended in time, space and linguistic coverage.
Temporally, we have focused here on relatively recent his-
torical populations from well-understood contexts (medieval
and post-medieval northwestern Europe) for pragmatic
(reliable contextual information, good preservation, access
to digitization technology, osteological expertise) and theor-
etical reasons (controversies about sexing using the lower
jaw, changes in food and nutrition, sound changes in the his-
tory of Dutch). But our experience clearly suggests that this
can be extended back in time for as far as there are well-pre-
served components of the vocal tract in the fossil record,
emphatically preceding the emergence of anatomically
modern humans a few hundred thousand years ago [140].
Geographically, there is nothing special about northwes-
tern Europe besides the fact that it is historically rather well
understood and archeologically intensively studied, but as
more work is conducted in other regions, as more osteologi-
cal and fossil data become available, either physically (in
museums and collections) or digitally (as three-dimensional
optical or CT scans), and as the various non-scientific
hurdles related to accessing these data diminish, this type
of investigation can be used to shed light on regional or
larger-scale developments.
Finally, we are guilty of producing yet another study of
vowel production here (although we do provide the formants
F1 to F5 and the spectra up to 5000 Hz), but this can be
extended to other speech sounds and vocal tract structures
as well. Just to cite a few possibilities, one could investigate
the alveolar ridge and its effects on click consonants
[91,141], hard palate shape and ‘r’[41], dentition/bite and
labiodentals [94], or larynx position and, indeed, vowels [4].
Putting these extensions together, we could suggest
studies that would, for example, look at the osteological
and fossil record of sub-Saharan Africa preceding the rela-
tively recent Bantu expansion [142,143], focusing on the
alveolar ridge and aiming to understand the time-depth
and geographical extensions of ‘click languages’. More pre-
cisely, while currently there are but a few languages that
integrate click consonants in their phonological inventories,
mostly in southern and eastern Africa (and some Bantu
languages that have borrowed clicks), there are intriguing
AB
CD
Figure 2. Midsagittal views (from the left) of the four reconstructed vocal
tracts (identified as A–D; see the electronic supplementary materials for
details). The airways are shown in blue, the associated skull samples are
in beige and the large capital black letters are the samples. Sample
access granted by the Stichting Cultureel Erfgoed Zeeland. Digitized image
dissemination for educational purposes only. Crania models created by
author W.A.B.; for access to the actual three-dimensional models of the
crania, contact author W.A.B. (Online version in colour.)
royalsocietypublishing.org/journal/rstb Phil. Trans. R. Soc. B 376: 20200192
7

suggestions that they are but remnants of a once widespread
use of phonemic clicks [144–146]. If the alveolar ridge shape
and size indeed bias the articulation and acoustics of clicks
[91,141], then we might be able to infer if past populations
were biased in such a way as to favour phonological clicks
or not. (Incidentally, we could apply the same inferences to
the existing pygmy groups: while their pre-Bantu languages
are lost, they may very well have used phonemic clicks
as well.)
Another example might even transgress the origins of
modern humans and try to infer features of Neanderthal
speech: if the negative effects of the edge-to-edge bite on
labiodentals inferred for recent hunter-gatherers [94] also
hold deeper in time, we can infer that pre-12 000 years ago
modern humans, archaic humans, Neanderthals (and even
H. erectus) probably did not use ‘f’and ‘v’that much [147].
Likewise, we might use the shape of the Neanderthal hard
palate to infer something about the vowels that their
languages might have used, or even how they might have
articulated their ‘r’s.
But we also need to know more about the type and pat-
terning of variation in vocal tract anatomy, physiology and
control in present-day humans, and its effects on speech
and language, before we can generate informed hypotheses
about the past. The work we presented here, concerning the
hard palate [41,88], the alveolar ridge [91], and the bite
[94], are (we hope) just the beginning of a vast research pro-
gramme. Other directions could concern the curvature of the
cervical spine and pitch [148,149], or the anatomy of the nasal
cavity and the anatomy and physiology of the velum and
vowel nasalization. While we do not know how widespread
this variation is and how important its effects on speech
and language are, the available evidence suggests that this
is a worthwhile direction of future research. In the end, the
breadth of these questions is only limited by our imagination,
the fossil and osteological data, and the kind of relationships
between vocal tract anatomy, sound change and linguistic
diversity that future work will establish.
Such investigations assume that the processes, forces and
mechanisms that we observe today (in particular, the effects
of vocal tract anatomy on speech and language) were also
at work in the past in pretty much the same way—what is
known as the uniformitarian principle. However, it is cur-
rently unclear how this principle should be applied in
practice, because the farther back in time we go the more
different things (gradually) become, until we cross into the
long evolutionary history preceding the emergence of
language as we know it [9,150]. Even closer to the present,
if the link between food, bite and labiodentals [94] holds,
then strict uniformitarianism breaks down at the dawn of
agriculture, as we cannot expect pre-12 000-years old
languages to have the same distribution of labiodentals as
present-day languages, but the uniformitarian principle
would still largely apply, as the same articulatory constraints
and affordances worked then as they do today. (For more
nuanced discussions and further developments, see [16], as
well as [151–153].)
Ethics. The ArtiVarK study is covered by the ethics approval
45659.091.14 (1 June 2015), Donders Center for Brain, Cognition
and Behaviour, Nijmegen, The Netherlands.
Data accessibility. The R code and data needed to reproduce the simu-
lation plots and results reported here and in the electronic
supplementary materials are freely available as described in the elec-
tronic supplementary materials. The 3D STL models of the four
crania used in the simulations are available upon request from
W.A.B.
Authors’contributions. D.D., S.R.M. and A.W.R. designed the research.
W.A.B. and A.M.B. collected and analysed the historical samples,
summarized the samples, described and plotted the landmarks.
S.R.M. collected and analysed the contemporaneous sample; per-
formed the biomechanical and acoustic simulations, analysed and
plotted their results. D.D. drafted the paper. All authors contributed
to the paper. All authors gave final approval for publication and
agree to be held accountable for the work performed therein.
Competing interests. The authors have no competing interests to declare.
Funding. This work was supported by funding from the Dutch
Research Council (grant no. NWO276-70-022), the European
Institutes for Advanced Study (grant no. EURIAS2017-2018) and
the French National Research Agency (ANR)/IDEXLyon ( grant no.
16-IDEX-0005).
Acknowledgements. We wish to thank our ArtiVarK participants; David
Norris and Paul Gaalman for access to and piloting on the Avanto
MRI scanner; Thomas Maal, Frans Delfos and Cees Kreulen for
access to and help with the TRIOS intra-oral scanner; Carly Jaques
for participant recruitment and management; John Esling for record-
ing the phonetic training materials; Sabine Kooijman for assistance
with ethics; Rachel Schats for assistance with the Alkmaar skeletal
collection. Sample access granted by the Stichting Cultureel Erfgoed
Zeeland. Digitized image dissemination for educational purposes
only. The osteological collections of Alkmaar and Middenbeemster
were analysed at the Laboratory for Human Osteoarchaeology, Fac-
ulty of Archaeology, Leiden University.
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