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The origin of speech refers to the more general problem of the origin of language in the context of the physiological development of the human speech organs such as the tongue, lips and vocal organs used to produce phonological units in all human languages.
Background
Although related to the more general problem of the origin of language, the evolution of distinctively human speech capacities has become a distinct and in many ways separate area of scientific research. The topic is a separate one because language is not necessarily spoken: it can equally be written or signed. Speech is in this sense optional, although it is the default modality for language.
Places of articulation (passive and active):
1.
Exo-labial, 2. Endo-labial, 3. Dental, 4. Alveolar, 5. Post-alveolar,
6. Pre-palatal, 7. Palatal, 8. Velar, 9. Uvular, 10. Pharyngeal, 11.
Glottal, 12. Epiglottal, 13. Radical, 14. Postero-dorsal, 15.
Antero-dorsal, 16. Laminal, 17. Apical, 18. Sub-apical
Uncontroversially, monkeys, apes and humans, like many other animals, have evolved specialised mechanisms for producing sound for purposes of social communication. On the other hand, no monkey or ape uses its tongue for such purposes.
Our species' unprecedented use of the tongue, lips and other moveable
parts seems to place speech in a quite separate category, making its
evolutionary emergence an intriguing theoretical challenge in the eyes
of many scholars.
Nevertheless, recent insights in human evolution - more
specifically our Pleistocene littoral evolution (e.g. Peter Rhys-Evans
2020 "The waterside ape" CRC Press) - help understand how human speech
evolved: different biological preadaptations to spoken language find
their origin in our waterside past, such as our larger brain (thanks to
DHA and other brain-specific nutrients in seafoods), voluntary breathing
(breath-hold diving for shellfish etc.) and suction feeding of
soft-slippery seafoods. Suction feeding explains why humans, as opposed
to other hominoids, evolved hyoidal descent (tongue-bone descended in
the throat), closed tooth-rows (with incisiform canine teeth) and a
globular tongue perfectly fitting in our vaulted and smooth palate
(without transverse ridges as in apes): all this allowed the
pronunciation of consonants. Other, probably older, preadaptations to
human speech are territorial songs and gibbon-like duetting (Darwin
1871) and vocal learning. Vocal learning, the ability to imitate sounds -
as in many birds and bats and a number of Cetacea and Pinnipedia - is
arguably required for locating or finding back (amid the foliage or in
the sea) the offspring or parents. Indeed, independent lines of evidence
(comparative, fossil, archeological, paleo-environmental, isotopic,
nutritional, and physiological) show that early-Pleistocene "archaic"
Homo spread intercontinentally along the Indian Ocean shores (they even
reached overseas islands such as Flores) where they regularly dived for
littoral foods such as shell- and crayfish (e.g. J. Joordens et al. 2015
"Homo erectus at Trinil on Java used shells for tool production and
engraving" 2015 Nature 518:228-231) which are extremely rich in
brain-specific nutrients, explaining Homo's brain enlargement (Stephen
Cunnane and Kathlyn Stewart eds 2010 "Human Brain Evolution: The
Influence of Freshwater and Marine Food Resources" Wiley-Blackwell).
Shallow-diving for seafoods requires voluntary airway control, a
prerequisite for spoken language. Seafood such as shellfish generally
does not require biting and chewing, but stone tool use and suction
feeding. This finer control of the oral apparatus was arguably another
biological preadaptation to human speech, especially for the production
of consonants (M. Verhaegen & S. Munro 2004 "Possible preadaptations
to speech – a preliminary comparative approach" Human Evolution
19:53-70).
Modality-independence
The term modality
means the chosen representational format for encoding and transmitting
information. A striking feature of language is that it is modality-independent.
Should an impaired child be prevented from hearing or producing sound,
its innate capacity to master a language may equally find expression in
signing. Sign languages of the deaf are independently invented and have
all the major properties of spoken language except for the modality of
transmission. From this it appears that the language centres of the human brain must have evolved to function optimally irrespective of the selected modality.
"The detachment from
modality-specific inputs may represent a substantial change in neural
organization, one that affects not only imitation but also
communication; only humans can lose one modality (e.g. hearing) and make
up for this deficit by communicating with complete competence in a
different modality (i.e. signing)."
— Marc Hauser, Noam Chomsky, and W. Tecumseh Fitch, 2002. The Faculty of Language: What Is It, Who Has It, and How Did It Evolve?
This feature is extraordinary. Animal communication systems routinely
combine visible with audible properties and effects, but no one is
modality-independent. No vocally impaired whale, dolphin or songbird,
for example, could express its song repertoire equally in visual
display. Indeed, in the case of animal communication, message and
modality are not capable of being disentangled. Whatever message is
being conveyed stems from the intrinsic properties of the signal.
Modality independence should not be confused with the ordinary
phenomenon of multimodality. Monkeys and apes rely on a repertoire of
species-specific "gesture-calls" — emotionally expressive vocalisations
inseparable from the visual displays which accompany them.
Humans also have species-specific gesture-calls — laughs, cries, sobs
and so forth — together with involuntary gestures accompanying speech. Many animal displays are polymodal in that each appears designed to exploit multiple channels simultaneously.
The human linguistic property of "modality independence" is
conceptually distinct from this. It allows the speaker to encode the
informational content of a message in a single channel while switching
between channels as necessary. Modern city-dwellers switch effortlessly
between the spoken word and writing in its various forms — handwriting,
typing, e-mail and so forth. Whichever modality is chosen, it can
reliably transmit the full message content without external assistance
of any kind. When talking on the telephone, for example, any
accompanying facial or manual gestures, however natural to the speaker,
are not strictly necessary. When typing or manually signing, conversely,
there's no need to add sounds. In many Australian Aboriginal cultures, a
section of the population — perhaps women observing a ritual taboo —
traditionally restrict themselves for extended periods to a silent
(manually signed) version of their language.
Then, when released from the taboo, these same individuals resume
narrating stories by the fireside or in the dark, switching to pure
sound without sacrifice of informational content.
Evolution of the speech organs
Speaking is the default modality for language in all cultures.
Humans' first recourse is to encode our thoughts in sound — a method
which depends on sophisticated capacities for controlling the lips,
tongue and other components of the vocal apparatus.
The speech organs, everyone agrees, evolved in the first instance
not for speech but for more basic bodily functions such as feeding and
breathing. Nonhuman primates have broadly similar organs, but with
different neural controls.
Apes use their highly flexible, maneuverable tongues for eating but not
for vocalizing. When an ape is not eating, fine motor control over
its tongue is deactivated. Either it is performing gymnastics with its tongue or it is vocalising; it cannot perform both activities simultaneously. Since this applies to mammals in general, Homo sapiens
is exceptional in harnessing mechanisms designed for respiration and
ingestion to the radically different requirements of articulate speech.
Tongue
Spectrogram of American English vowels
[i, u, ɑ] showing the formants
f1 and
f2 The word "language" derives from the Latin lingua, "tongue".
Phoneticians agree that the tongue is the most important speech
articulator, followed by the lips. A natural language can be viewed as a
particular way of using the tongue to express thought.
The human tongue has an unusual shape. In most mammals, it is a
long, flat structure contained largely within the mouth. It is attached
at the rear to the hyoid bone, situated below the oral level in the pharynx. In humans, the tongue has an almost circular sagittal (midline) contour, much of it lying vertically down an extended pharynx,
where it is attached to a hyoid bone in a lowered position. Partly as a
result of this, the horizontal (inside-the-mouth) and vertical
(down-the-throat) tubes forming the supralaryngeal vocal tract (SVT) are
almost equal in length (whereas in other species, the vertical section
is shorter). As we move our jaws up and down, the tongue can vary the
cross-sectional area of each tube independently by about 10:1, altering
formant frequencies accordingly. That the tubes are joined at a right
angle permits pronunciation of the vowels [i], [u] and [a], which nonhuman primates cannot do.
Even when not performed particularly accurately, in humans the
articulatory gymnastics needed to distinguish these vowels yield
consistent, distinctive acoustic results, illustrating the quantal nature of human speech sounds. It may not be coincidental that [i], [u] and [a] are the most common vowels in the world's languages.
Human tongues are a lot shorter and thinner than other mammals and are
composed of a large number of muscles, which helps shape a variety of
sounds within the oral cavity. The diversity of sound production is also
increased with the human’s ability to open and close the airway,
allowing varying amounts of air to exit through the nose. The fine motor
movements associated with the tongue and the airway, make humans more
capable of producing a wide range of intricate shapes in order to
produce sounds at different rates and intensities.
Lips
In humans, the lips are important for the production of stops and fricatives, in addition to vowels.
Nothing, however, suggests that the lips evolved for those reasons.
During primate evolution, a shift from nocturnal to diurnal activity in tarsiers, monkeys and apes (the haplorhines) brought with it an increased reliance on vision at the expense of olfaction. As a result, the snout became reduced and the rhinarium
or "wet nose" was lost. The muscles of the face and lips consequently
became less constrained, enabling their co-option to serve purposes of
facial expression. The lips also became thicker, and the oral cavity
hidden behind became smaller.
"Hence", according to one major authority, "the evolution of mobile,
muscular lips, so important to human speech, was the exaptive result of
the evolution of diurnality and visual communication in the common
ancestor of haplorhines". It is unclear whether our lips have undergone a more recent adaptation to the specific requirements of speech.
Respiratory control
Compared
with nonhuman primates, humans have significantly enhanced control of
breathing, enabling exhalations to be extended and inhalations shortened
as we speak. While we are speaking, intercostal and interior abdominal
muscles are recruited to expand the thorax and draw air into the lungs,
and subsequently to control the release of air as the lungs deflate. The
muscles concerned are markedly more innervated in humans than in
nonhuman primates.
Evidence from fossil hominins suggests that the necessary enlargement
of the vertebral canal, and therefore spinal cord dimensions, may not
have occurred in Australopithecus or Homo erectus but was present in the Neanderthals and early modern humans.
Larynx
The larynx or voice box is an organ in the neck housing the vocal folds, which are responsible for phonation. In humans, the larynx is descended,
it is positioned lower than in other primates.This is because the
evolution of humans to an upright position shifted the head directly
above the spinal cord, forcing everything else downward. The
repositioning of the larynx resulted in a longer cavity called the
pharynx, which is responsible for increasing the range and clarity of
the sound being produced. Other primates have almost no pharynx;
therefore, their vocal power is significantly lower. Our species is not unique in this respect: goats, dogs, pigs and tamarins lower the larynx temporarily, to emit loud calls.
Several deer species have a permanently lowered larynx, which may be
lowered still further by males during their roaring displays. Lions, jaguars, cheetahs and domestic cats also do this.
However, laryngeal descent in nonhumans (according to Philip Lieberman)
is not accompanied by descent of the hyoid; hence the tongue remains
horizontal in the oral cavity, preventing it from acting as a pharyngeal
articulator.
Anterolateral view of head and neck
Despite all this, scholars remain divided as to how "special" the
human vocal tract really is. It has been shown that the larynx does
descend to some extent during development in chimpanzees, followed by
hyoidal descent.
As against this, Philip Lieberman points out that only humans have
evolved permanent and substantial laryngeal descent in association with
hyoidal descent, resulting in a curved tongue and two-tube vocal tract
with 1:1 proportions. Uniquely in the human case, simple contact between
the epiglottis and velum is no longer possible, disrupting the normal
mammalian separation of the respiratory and digestive tracts during
swallowing. Since this entails substantial costs — increasing the risk
of choking while swallowing food — we are forced to ask what benefits
might have outweighed those costs. The obvious benefit — so it is
claimed — must have been speech. But this idea has been vigorously
contested. One objection is that humans are in fact not seriously at risk of choking on food: medical statistics indicate that accidents of this kind are extremely rare.
Another objection is that in the view of most scholars, speech as we
know it emerged relatively late in human evolution, roughly
contemporaneously with the emergence of Homo sapiens.
A development as complex as the reconfiguration of the human vocal
tract would have required much more time, implying an early date of
origin. This discrepancy in timescales undermines the idea that human
vocal flexibility was initially driven by selection pressures for speech.
At least one orangutan has demonstrated the ability to control the voice box.
The size exaggeration hypothesis
To lower the larynx is to increase the length of the vocal tract, in turn lowering formant
frequencies so that the voice sounds "deeper" — giving an impression of
greater size. John Ohala argues that the function of the lowered larynx
in humans, especially males, is probably to enhance threat displays
rather than speech itself.
Ohala points out that if the lowered larynx were an adaptation for
speech, we would expect adult human males to be better adapted in this
respect than adult females, whose larynx is considerably less low. In
fact, females invariably outperform males in verbal tests, falsifying
this whole line of reasoning. W. Tecumseh Fitch likewise argues that
this was the original selective advantage of laryngeal lowering in our
species. Although (according to Fitch) the initial lowering of the
larynx in humans had nothing to do with speech, the increased range of
possible formant patterns was subsequently co-opted for speech. Size
exaggeration remains the sole function of the extreme laryngeal descent
observed in male deer. Consistent with the size exaggeration hypothesis,
a second descent of the larynx occurs at puberty in humans, although
only in males. In response to the objection that the larynx is descended
in human females, Fitch suggests that mothers vocalizing to protect
their infants would also have benefited from this ability.
Neanderthal Speech
Hyoid bone — anterior surface, enlarged
Most specialists credit the Neanderthals with speech abilities not radically different from those of modern Homo sapiens.
An indirect line of argument is that their tool-making and hunting
tactics would have been difficult to learn or execute without some kind
of speech. A recent extraction of DNA from Neanderthal bones indicates that Neanderthals had the same version of the FOXP2
gene as modern humans. This gene, once mistakenly described as the
"grammar gene", plays a role in controlling the orofacial movements
which (in modern humans) are involved in speech.
During the 1970s, it was widely believed that the Neanderthals lacked modern speech capacities.
It was claimed that they possessed a hyoid bone so high up in the vocal
tract as to preclude the possibility of producing certain vowel sounds.
The hyoid bone is present in many mammals.
It allows a wide range of tongue, pharyngeal and laryngeal movements by
bracing these structures alongside each other in order to produce
variation. It is now realised that its lowered position is not unique to Homo sapiens,
while its relevance to vocal flexibility may have been overstated:
although men have a lower larynx, they do not produce a wider range of
sounds than women or two-year-old babies. There is no evidence that the
larynx position of the Neanderthals impeded the range of vowel sounds
they could produce. The discovery of a modern-looking hyoid bone of a Neanderthal man in the Kebara Cave in Israel led its discoverers to argue that the Neanderthals had a descended larynx, and thus human-like speech capabilities. However, other researchers have claimed that the morphology of the hyoid is not indicative of the larynx's position.
It is necessary to take into consideration the skull base, the mandible
and the cervical vertebrae and a cranial reference plane.
The morphology of the outer and middle ear of Middle Pleistocene hominins from Atapuerca
SH in Spain, believed to be proto-Neanderthal, suggests they had an
auditory sensitivity similar to modern humans and very different from
chimpanzees. They were probably able to differentiate between many
different speech sounds.
Hypoglossal canal
The hypoglossal nerve plays an important role in controlling
movements of the tongue. In 1998, one research team used the size of the
hypoglossal canal in the base of fossil skulls in an attempt to
estimate the relative number of nerve fibres, claiming on this basis
that Middle Pleistocene hominins and Neanderthals had more fine-tuned
tongue control than either australopithecines or apes. Subsequently, however, it was demonstrated that hypoglossal canal size and nerve sizes are not correlated, and it is now accepted that such evidence is uninformative about the timing of human speech evolution.
Origin of speech sounds
Distinctive features theory
According to one influential school,
the human vocal apparatus is intrinsically digital on the model of a
keyboard or digital computer. If so, this is remarkable: nothing about a
chimpanzee's vocal apparatus suggests a digital keyboard,
notwithstanding the anatomical and physiological similarities. This
poses the question as to when and how, during the course of human
evolution, the transition from analog to digital structure and function
occurred.
The human supralaryngeal tract is said to be digital in the sense
that it is an arrangement of moveable toggles or switches, each of
which, at any one time, must be in one state or another. The vocal
cords, for example, are either vibrating (producing a sound) or not
vibrating (in silent mode). By virtue of simple physics, the
corresponding distinctive feature —
in this case, "voicing" — cannot be somewhere in between. The options
are limited to "off" and "on". Equally digital is the feature known as "nasalisation". At any given moment the soft palate
or velum either allows or doesn't allow sound to resonate in the nasal
chamber. In the case of lip and tongue positions, more than two digital
states may be allowed.
The theory that speech sounds are composite entities constituted
by complexes of binary phonetic features was first advanced in 1938 by
the Russian linguist Roman Jakobson. A prominent early supporter of this approach was Noam Chomsky, who went on to extend it from phonology to language more generally, in particular to the study of syntax and semantics. In his 1965 book, Aspects of the Theory of Syntax,
Chomsky treated semantic concepts as combinations of binary-digital
atomic elements explicitly on the model of distinctive features theory.
The lexical item "bachelor", on this basis, would be expressed as [+
Human], [+ Male], [- Married].
Supporters of this approach view the vowels and consonants
recognized by speakers of a particular language or dialect at a
particular time as cultural entities of little scientific interest. From
a natural science standpoint, the units which matter are those common
to Homo sapiens by virtue of our biological nature. By combining
the atomic elements or "features" with which all humans are innately
equipped, anyone may in principle generate the entire range of vowels
and consonants to be found in any of the world's languages, whether
past, present or future. The distinctive features are in this sense
atomic components of a universal language.
Voicing contrast in English fricatives
| Articulation
|
Voiceless
|
Voiced
|
| Pronounced with the lower lip against the teeth:
|
[f] (fan)
|
[v] (van)
|
| Pronounced with the tongue against the teeth:
|
[θ] (thin, thigh)
|
[ð] (then, thy)
|
| Pronounced with the tongue near the gums:
|
[s] (sip)
|
[z] (zip)
|
| Pronounced with the tongue bunched up:
|
[ʃ] (pressure)
|
[ʒ] (pleasure)
|
Criticism
In
recent years, the notion of an innate "universal grammar" underlying
phonological variation has been called into question. The most
comprehensive monograph ever written about speech sounds, Sounds of the World's Languages, by Peter Ladefoged and Ian Maddieson,
found virtually no basis for the postulation of some small number of
fixed, discrete, universal phonetic features. Examining 305 languages,
for example, they encountered vowels that were positioned basically
everywhere along the articulatory and acoustic continuum. Ladefoged
concludes that phonological features are not determined by human nature:
"Phonological features are best regarded as artifacts that linguists
have devised in order to describe linguistic systems." The controversy remains unresolved.
Self-organization theory
Self-organization
characterizes systems where macroscopic structures are spontaneously
formed out of local interactions between the many components of the
system.
In self-organized systems, global organizational properties are not to
be found at the local level. In colloquial terms, self-organization is
roughly captured by the idea of "bottom-up" (as opposed to "top-down")
organization. Examples of self-organized systems range from ice crystals
to galaxy spirals in the inorganic world, and from spots on the leopard
skins to the architecture of termite nests or shape of a flock of
starlings.
A termite mound (Macrotermitinae) in the Okavango Delta just outside
Maun,
BotswanaAccording to many phoneticians, the sounds of language arrange and re-arrange themselves through self-organization
Speech sounds have both perceptual ("how you hear them") and
articulatory ("how you produce them") properties, all with continuous
values. Speakers tend to minimize effort, favoring ease of articulation
over clarity. Listeners do the opposite, favoring sounds that are easy
to distinguish even if difficult to pronounce. Since speakers and
listeners are constantly switching roles, the syllable systems actually
found in the world's languages turn out to be a compromise between
acoustic distinctiveness on the one hand, and articulatory ease on the
other.
How, precisely, do systems of vowels, consonants and syllables
arise? Agent-based computer models take the perspective of
self-organisation at the level of the speech community or population.
The two main paradigms here are (1) the iterated learning model and (2)
the language game model. Iterated learning focuses on transmission from
generation to generation, typically with just one agent in each
generation.
In the language game model, a whole population of agents simultaneously
produce, perceive and learn language, inventing novel forms when the
need arises.
Several models have shown how relatively simple peer-to-peer
vocal interactions, such as imitation, can spontaneously self-organize a
system of sounds shared by the whole population, and different in
different populations. For example, models elaborated by Berrah et al., as well as de Boer, and recently reformulated using Bayesian theory,
showed how a group of individuals playing imitation games can
self-organize repertoires of vowel sounds which share substantial
properties with human vowel systems. For example, in de Boer's model,
initially vowels are generated randomly, but agents learn from each
other as they interact repeatedly over time. Agent A chooses a vowel
from her repertoire and produces it, inevitably with some noise. Agent B
hears this vowel and chooses the closest equivalent from her own
repertoire. To check whether this truly matches the original, B produces
the vowel she thinks she has heard, whereupon A refers once
again to her own repertoire to find the closest equivalent. If this
matches the one she initially selected, the game is successful,
otherwise, it has failed. "Through repeated interactions," according to
de Boer, "vowel systems emerge that are very much like the ones found in
human languages."
In a different model, the phonetician Björn Lindblom
was able to predict, on self-organizational grounds, the favored
choices of vowel systems ranging from three to nine vowels on the basis
of a principle of optimal perceptual differentiation.
Further models studied the role of self-organization in the
origins of phonemic coding and combinatoriality, which is the existence
of phonemes and their systematic reuse to build structured syllables. Pierre-Yves Oudeyer
developed models which showed that basic neural equipment for adaptive
holistic vocal imitation, coupling directly motor and perceptual
representations in the brain, can generate spontaneously shared
combinatorial systems of vocalizations, including phonotactic patterns,
in a society of babbling individuals.
These models also characterized how morphological and physiological
innate constraints can interact with these self-organized mechanisms to
account for both the formation of statistical regularities and diversity
in vocalization systems.
Gestural theory
The
gestural theory states that speech was a relatively late development,
evolving by degrees from a system that was originally gestural. Our
ancestors were unable to control their vocalization at the time when
gestures were used to communicate; however, as they slowly began to
control their vocalizations, spoken language began to evolve.
Three types of evidence support this theory:
- Gestural language and vocal language depend on similar neural systems. The regions on the cortex that are responsible for mouth and hand movements border each other.
- Nonhuman primates
minimize vocal signals in favor of manual, facial and other visible
gestures in order to express simple concepts and communicative
intentions in the wild. Some of these gestures resemble those of humans,
such as the "begging posture", with the hands stretched out, which
humans share with chimpanzees.
- Mirror Neurons
Research has found strong support for the idea that spoken language
and signing depend on similar neural structures. Patients who used sign
language, and who suffered from a left-hemisphere lesion, showed the same disorders with their sign language as vocal patients did with their oral language.
Other researchers found that the same left-hemisphere brain regions
were active during sign language as during the use of vocal or written
language.0
Humans spontaneously use hand and facial gestures when formulating ideas to be conveyed in speech. There are also, of course, many sign languages in existence, commonly associated with deaf
communities; as noted above, these are equal in complexity,
sophistication, and expressive power, to any oral language. The main
difference is that the "phonemes" are produced on the outside of the
body, articulated with hands, body, and facial expression, rather than
inside the body articulated with tongue, teeth, lips, and breathing.
Many psychologists and scientists have looked into the mirror
system in the brain to answer this theory as well as other behavioral
theories. Evidence to support mirror neurons as a factor in the
evolution of speech includes mirror neurons in primates, the success of
teaching apes to communicate gesturally, and pointing/gesturing to teach
young children language. Fogassi and Ferrari (2014) monitored motor
cortex activity in monkeys, specifically area F5 in the Broca’s area,
where mirror neurons are located. They observed changes in electrical
activity in this area when the monkey executed or observed different
hand actions performed by someone else. Broca’s area is a region in the
frontal lobe responsible for language production and processing. The
discovery of mirror neurons in this region, which fire when an action is
done or observed specifically with the hand, strongly supports the
belief that communication was once accomplished with gestures. The same
is true when teaching young children language. When one points at a
specific object or location, mirror neurons in the child fire as though
they were doing the action, which results in long term learning.
Criticism
Critics
note that for mammals in general, sound turns out to be the best medium
in which to encode information for transmission over distances at
speed. Given the probability that this applied also to early humans,
it's hard to see why they should have abandoned this efficient method in
favor of more costly and cumbersome systems of visual gesturing — only
to return to sound at a later stage.
By way of explanation, it has been proposed that at a relatively
late stage in human evolution, our ancestors' hands became so much in
demand for making and using tools that the competing demands of manual
gesturing became a hindrance. The transition to spoken language is said
to have occurred only at that point.
Since humans throughout evolution have been making and using tools,
however, most scholars remain unconvinced by this argument. (For a
different approach to this puzzle — one setting out from considerations
of signal reliability and trust — see "from pantomime to speech" below).
Timeline of Speech Evolution
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Little is known about the timing of language's emergence in the human
species. Unlike writing, speech leaves no material trace, making it
archaeologically invisible. Lacking direct linguistic evidence,
specialists in human origins have resorted to the study of anatomical
features and genes arguably associated with speech production. While
such studies may provide information as to whether pre-modern Homo species had speech capacities,
it is still unknown whether they actually spoke. While they may have
communicated vocally, the anatomical and genetic data lack the
resolution necessary to differentiate proto-language from speech.
Using statistical methods to estimate the time required to achieve the current spread and diversity in modern languages today, Johanna Nichols —
a linguist at the University of California, Berkeley — argued in 1998
that vocal languages must have begun diversifying in our species at
least 100,000 years ago.
More recently — in 2012 — anthropologists Charles Perreault and
Sarah Mathew used phonemic diversity to suggest a date consistent with
this.
"Phonemic diversity" denotes the number of perceptually distinct units
of sound — consonants, vowels and tones — in a language. The current
worldwide pattern of phonemic diversity potentially contains the
statistical signal of the expansion of modern Homo sapiens out of
Africa, beginning around 60-70 thousand years ago. Some scholars argue
that phonemic diversity evolves slowly and can be used as a clock to
calculate how long the oldest African languages would have to have been
around in order to accumulate the number of phonemes they possess today.
As human populations left Africa and expanded into the rest of the
world, they underwent a series of bottlenecks — points at which only a
very small population survived to colonise a new continent or region.
Allegedly such a population crash led to a corresponding reduction in
genetic, phenotypic and phonemic diversity. African languages
today have some of the largest phonemic inventories in the world, while
the smallest inventories are found in South America and Oceania, some
of the last regions of the globe to be colonized. For example, Rotokas, a language of New Guinea, and Pirahã, spoken in South America, both have just 11 phonemes, while !Xun, a language spoken in Southern Africa has 141 phonemes.
The authors use a natural experiment — the colonization of mainland Southeast Asia on the one hand, the long-isolated Andaman Islands
on the other — to estimate the rate at which phonemic diversity
increases through time. Using this rate, they estimate that the world's
languages date back to the Middle Stone Age
in Africa, sometime between 350 thousand and 150 thousand years ago.
This corresponds to the speciation event which gave rise to Homo sapiens.
These and similar studies have however been criticized by
linguists who argue that they are based on a flawed analogy between
genes and phonemes, since phonemes are frequently transferred laterally
between languages unlike genes, and on a flawed sampling of the world's
languages, since both Oceania and the Americas also contain languages
with very high numbers of phonemes, and Africa contains languages with
very few. They argue that the actual distribution of phonemic diversity
in the world reflects recent language contact and not deep language
history - since it is well demonstrated that languages can lose or gain
many phonemes over very short periods. In other words, there is no valid
linguistic reason to expect genetic founder effects to influence
phonemic diversity.
Speculative scenarios
Early speculations
"I
cannot doubt that language owes its origin to the imitation and
modification, aided by signs and gestures, of various natural sounds,
the voices of other animals, and man's own instinctive cries."
— Charles Darwin, 1871. The Descent of Man, and Selection in Relation to Sex.
In 1861, historical linguist Max Müller published a list of speculative theories concerning the origins of spoken language:
These theories have been grouped under the category named invention
hypotheses. These hypotheses were all meant to understand how the first
language could have developed and postulate that human mimicry of
natural sounds were how the first words with meaning were derived.
- Bow-wow. The bow-wow or cuckoo theory, which Müller attributed to the German philosopher Johann Gottfried Herder,
saw early words as imitations of the cries of beasts and birds. This
theory, believed to be derived from onomatopoeia, relates the meaning of
the sound to the actual sound formulated by the speaker.
- Pooh-pooh. The Pooh-Pooh theory saw the first words as emotional interjections and exclamations
triggered by pain, pleasure, surprise and so on. These sounds were all
produced on sudden intakes of breath, which is unlike any other
language. Unlike emotional reactions, spoken language is produced on the
exhale, so the sounds contained in this form of communication are
unlike those used in normal speech production, which makes this theory a
less plausible one for language acquisition.
- Ding-dong. Müller suggested what he called the Ding-Dong
theory, which states that all things have a vibrating natural
resonance, echoed somehow by man in his earliest words. Words are
derived from the sound associated with their meaning; for example, “crash became a word for thunder, boom for explosion.” This theory also heavily relies on the concept of onomatopoeia.
- Yo-he-ho. The yo-he-ho theory saw language emerging
out of collective rhythmic labor, the attempt to synchronize muscular
effort resulting in sounds such as heave alternating with sounds such as ho.
Believed to be derived from the basis of human collaborative efforts,
this theory states that humans needed words, which might have started
off as chanting, to communicate. This need could have been to ward off
predators, or served as a unifying battle cry.
- Ta-ta. This did not feature in Max Müller's list, having been proposed in 1930 by Sir Richard Paget. According to the ta-ta theory, humans made the earliest words by tongue movements that mimicked manual gestures, rendering them audible.
A common concept of onomatopoeia as the first source of words is
present; however, there is a glaring problem with this theory.
Onomatopoeia can explain the first couple of words all derived from
natural phenomenon, but there is no explanation as to how more complex
words without a natural counterpart came to be.
Most scholars today consider all such theories not so much wrong — they
occasionally offer peripheral insights — as comically naïve and
irrelevant.
The problem with these theories is that they are so narrowly
mechanistic. They assume that once our ancestors had stumbled upon the
appropriate ingenious mechanism for linking sounds with meanings, language automatically evolved and changed.
Problems of reliability and deception
From
the perspective of modern science, the main obstacle to the evolution
of speech-like communication in nature is not a mechanistic one. Rather,
it is that symbols — arbitrary associations of sounds with
corresponding meanings — are unreliable and may well be false. As the saying goes, "words are cheap". The problem of reliability was not recognised at all by Darwin, Müller or the other early evolutionist theorists.
Animal vocal signals are for the most part intrinsically
reliable. When a cat purrs, the signal constitutes direct evidence of
the animal's contented state. One can "trust" the signal not because the
cat is inclined to be honest, but because it just can't fake that
sound. Primate vocal calls may be slightly more manipulable, but they remain reliable for the same reason — because they are hard to fake. Primate social intelligence is Machiavellian —
self-serving and unconstrained by moral scruples. Monkeys and apes
often attempt to deceive one another, while at the same time constantly
on guard against falling victim to deception themselves.
Paradoxically, it is precisely primates' resistance to deception that
blocks the evolution of their vocal communication systems along
language-like lines. Language is ruled out because the best way to guard
against being deceived is to ignore all signals except those that are
instantly verifiable. Words automatically fail this test.
Words are easy to fake. Should they turn out to be lies,
listeners will adapt by ignoring them in favor of hard-to-fake indices
or cues. For language to work, then, listeners must be confident that
those with whom they are on speaking terms are generally likely to be
honest. A peculiar feature of language is "displaced reference", which means
reference to topics outside the currently perceptible situation. This
property prevents utterances from being corroborated in the immediate
"here" and "now". For this reason, language presupposes relatively high
levels of mutual trust in order to become established over time as an evolutionarily stable strategy.
A theory of the origins of language must, therefore, explain why humans
could begin trusting cheap signals in ways that other animals
apparently cannot (see signalling theory).
"Kin selection"
The "mother tongues" hypothesis was proposed in 2004 as a possible solution to this problem. W. Tecumseh Fitch suggested that the Darwinian principle of "kin selection" —
the convergence of genetic interests between relatives — might be part
of the answer. Fitch suggests that spoken languages were originally
"mother tongues". If speech evolved initially for communication between
mothers and their own biological offspring, extending later to include
adult relatives as well, the interests of speakers and listeners would
have tended to coincide. Fitch argues that shared genetic interests
would have led to sufficient trust and cooperation for intrinsically
unreliable vocal signals — spoken words — to become accepted as
trustworthy and so begin evolving for the first time.
Criticism
Critics
of this theory point out that kin selection is not unique to humans.
Ape mothers also share genes with their offspring, as do all animals, so
why is it only humans who speak? Furthermore, it is difficult to
believe that early humans restricted linguistic communication to genetic
kin: the incest taboo must have forced men and women to interact and
communicate with non-kin. So even if we accept Fitch's initial premises,
the extension of the posited "mother tongue" networks from relatives to
non-relatives remains unexplained.
"Reciprocal altruism"
Ib Ulbæk invokes another standard Darwinian principle — "reciprocal altruism" —
to explain the unusually high levels of intentional honesty necessary
for language to evolve. 'Reciprocal altruism' can be expressed as the
principle that if you scratch my back, I'll scratch yours. In linguistic terms, it would mean that if you speak truthfully to me, I'll speak truthfully to you.
Ordinary Darwinian reciprocal altruism, Ulbæk points out, is a
relationship established between frequently interacting individuals. For
language to prevail across an entire community, however, the necessary
reciprocity would have needed to be enforced universally instead of
being left to individual choice. Ulbæk concludes that for language to
evolve, early society as a whole must have been subject to moral
regulation.
Criticism
Critics
point out that this theory fails to explain when, how, why or by whom
"obligatory reciprocal altruism" could possibly have been enforced.
Various proposals have been offered to remedy this defect.
A further criticism is that language doesn't work on the basis of
reciprocal altruism anyway. Humans in conversational groups don't
withhold information to all except listeners likely to offer valuable
information in return. On the contrary, they seem to want to advertise
to the world their access to socially relevant information, broadcasting
it to anyone who will listen without thought of return.
"Gossip and grooming"
Gossip, according to Robin Dunbar, does for group-living humans what manual grooming
does for other primates — it allows individuals to service their
relationships and so maintain their alliances. As humans began living in
larger and larger social groups, the task of manually grooming all
one's friends and acquaintances became so time-consuming as to be
unaffordable. In response to this problem, humans invented "a cheap and
ultra-efficient form of grooming" — vocal grooming. To keep your
allies happy, you now needed only to "groom" them with low-cost vocal
sounds, servicing multiple allies simultaneously while keeping both
hands free for other tasks. Vocal grooming (the production of pleasing
sounds lacking syntax or combinatorial semantics) then evolved somehow
into syntactical speech.
Criticism
Critics
of this theory point out that the very efficiency of "vocal grooming" —
that words are so cheap — would have undermined its capacity to signal
commitment of the kind conveyed by time-consuming and costly manual
grooming.
A further criticism is that the theory does nothing to explain the
crucial transition from vocal grooming — the production of pleasing but
meaningless sounds — to the cognitive complexities of syntactical
speech.
From pantomime to speech
According to another school of thought, language evolved from mimesis — the "acting out" of scenarios using vocal and gestural pantomime.
Charles Darwin, who himself was skeptical, hypothesized that human
speech and language is derived from gestures and mouth pantomime. This theory, further elaborated on by various authors, postulates that the genus Homo,
different from our ape ancestors, evolved a new type of cognition. Apes
are capable of associational learning. They can tie a sensory cue to a
motor response often trained through classical conditioning.
However, in apes, the conditioned sensory cue is necessary for a
conditioned response to be observed again. The motor response will not
occur without an external cue from an outside agent. A remarkable
ability that humans possess is the ability to voluntarily retrieve
memories without the need for a cue (e.g. conditioned stimulus). This is
not an ability that has been observed in animals except
language-trained apes. There is still much controversy on whether
pantomime is a capability for apes, both wild and captured.
For as long as utterances needed to be emotionally expressive and
convincing, it was not possible to complete the transition to purely
conventional signs.
On this assumption, pre-linguistic gestures and vocalisations would
have been required not just to disambiguate intended meanings, but also
to inspire confidence in their intrinsic reliability. If contractual commitments
were necessary in order to inspire community-wide trust in
communicative intentions, it would follow that these had to be in place
before humans could shift at last to an ultra-efficient, high-speed —
digital as opposed to analog — signalling format. Vocal distinctive features
(sound contrasts) are ideal for this purpose. It is therefore suggested
that the establishment of contractual understandings enabled the
decisive transition from mimetic gesture to fully conventionalised,
digitally encoded speech.
"Ritual/speech coevolution"
The ritual/speech coevolution theory was originally proposed by the distinguished social anthropologist Roy Rappaport before being elaborated by anthropologists such as Chris Knight, Jerome Lewis, Nick Enfield, Camilla Power and Ian Watts. Cognitive scientist and robotics engineer Luc Steels is another prominent supporter of this general approach, as is biological anthropologist/neuroscientist Terrence Deacon.
These scholars argue that there can be no such thing as a "theory
of the origins of language". This is because language is not a separate
adaptation but an internal aspect of something much wider — namely,
human symbolic culture as a whole.
Attempts to explain language independently of this wider context have
spectacularly failed, say these scientists, because they are addressing a
problem with no solution. Can we imagine a historian attempting to
explain the emergence of credit cards independently of the wider system
of which they are a part? Using a credit card makes sense only if you
have a bank account institutionally recognized within a certain kind of
advanced capitalist society — one where communications technology has
already been invented and fraud can be detected and prevented. In much
the same way, language would not work outside a specific array of social
mechanisms and institutions. For example, it would not work for an ape
communicating with other apes in the wild. Not even the cleverest ape
could make language work under such conditions.
"Lie and alternative, inherent in
language, ... pose problems to any society whose structure is founded on
language, which is to say all human societies. I have therefore argued
that if there are to be words at all it is necessary to establish The Word, and that The Word is established by the invariance of liturgy."
Advocates of this school of thought point out that words are cheap. As
digital hallucinations, they are intrinsically unreliable. Should an
especially clever ape, or even a group of articulate apes, try to use
words in the wild, they would carry no conviction. The primate
vocalizations that do carry conviction — those they actually
use — are unlike words, in that they are emotionally expressive,
intrinsically meaningful and reliable because they are relatively costly
and hard to fake.
Speech consists of digital contrasts whose cost is essentially
zero. As pure social conventions, signals of this kind cannot evolve in a
Darwinian social world — they are a theoretical impossibility.
Being intrinsically unreliable, language works only if you can build up
a reputation for trustworthiness within a certain kind of society —
namely, one where symbolic cultural facts (sometimes called
"institutional facts") can be established and maintained through
collective social endorsement. In any hunter-gatherer society, the basic mechanism for establishing trust in symbolic cultural facts is collective ritual.
Therefore, the task facing researchers into the origins of language is
more multidisciplinary than is usually supposed. It involves addressing
the evolutionary emergence of human symbolic culture as a whole, with
language an important but subsidiary component.
Criticism
Critics of the theory include Noam Chomsky,
who terms it the "non-existence" hypothesis — a denial of the very
existence of language as an object of study for natural science. Chomsky's own theory is that language emerged in an instant and in perfect form,
prompting his critics in turn to retort that only something that
doesn't exist — a theoretical construct or convenient scientific
fiction — could possibly emerge in such a miraculous way. The controversy remains unresolved.
Twentieth century speculations
Festal origins
The essay "The festal origin of human speech", though published in the late nineteenth century, made little impact until the American philosopher Susanne Langer re-discovered and publicised it in 1941.
"In
the early history of articulate sounds they could make no meaning
themselves, but they preserved and got intimately associated with the
peculiar feelings and perceptions that came most prominently into the
minds of the festal players during their excitement."
— J. Donovan, 1891. The Festal Origin of Human Speech.
The theory sets out from the observation that primate vocal sounds are above all emotionally
expressive. The emotions aroused are socially contagious. Because of
this, an extended bout of screams, hoots or barks will tend to express
not just the feelings of this or that individual but the mutually
contagious ups and downs of everyone within earshot.
Turning to the ancestors of Homo sapiens, the "festal
origin" theory suggests that in the "play-excitement" preceding or
following a communal hunt or other group activity, everyone might have
combined their voices in a comparable way, emphasizing their mood of
togetherness with such noises as rhythmic drumming and hand-clapping.
Variably pitched voices would have formed conventional patterns, such
that choral singing became an integral part of communal celebration.
Although this was not yet speech, according to Langer, it
developed the vocal capacities from which speech would later derive.
There would be conventional modes of ululating, clapping or dancing
appropriate to different festive occasions, each so intimately
associated with that kind of occasion that it would tend to
collectively uphold and embody the concept of it. Anyone hearing a
snatch of sound from such a song would recall the associated occasion
and mood. A melodic, rhythmic sequence of syllables conventionally
associated with a certain type of celebration would become, in effect,
its vocal mark. On that basis, certain familiar sound sequences would
become "symbolic".
In support of all this, Langer cites ethnographic reports of
tribal songs consisting entirely of "rhythmic nonsense syllables". She
concedes that an English equivalent such as "hey-nonny-nonny", although
perhaps suggestive of certain feelings or ideas, is neither noun, verb,
adjective, nor any other syntactical part of speech. So long as
articulate sound served only in the capacity of "hey nonny-nonny",
"hallelujah" or "alack-a-day", it cannot yet have been speech. For that
to arise, according to Langer, it was necessary for such sequences to be
emitted increasingly out of context — outside the total
situation that gave rise to them. Extending a set of associations from
one cognitive context to another, completely different one, is the
secret of metaphor. Langer invokes an early version of what is
nowadays termed "grammaticalization" theory to show how, from, such a
point of departure, syntactically complex speech might progressively
have arisen.
Langer acknowledges Emile Durkheim as having proposed a strikingly similar theory back in 1912. For recent thinking along broadly similar lines, see Steven Brown on "musilanguage", Chris Knight on "ritual" and "play", Jerome Lewis on "mimicry", Steven Mithen on "Hmmmmm" Bruce Richman on "nonsense syllables" and Alison Wray on "holistic protolanguage".
Mirror neuron hypothesis (MSH) and the Motor Theory of Speech Perception
Mirror
Neurons, originally found in the macaque monkey, are neurons which are
activated in both the action-performer and action-observer. This is a
proposed mechanism in humans.
The mirror neuron hypothesis, based on a phenomenon discovered in
2008 by Rizzolatti and Fabbri, supports the motor theory of speech
perception. The motor theory of speech perception was proposed in 1967
by Liberman, who believed that the motor system and language systems
were closely interlinked.
This would result in a more streamlined process of generating speech;
both the cognition and speech formulation could occur simultaneously.
Essentially, it is wasteful to have a speech decoding and speech
encoding process independent of each other. This hypothesis was further
supported by the discovery of motor neurons. Rizzolatti and Fabbri found
that there were specific neurons in the motor cortex of macaque monkeys
which were activated when seeing an action.
The neurons which are activated are the same neurons in which would be
required to perform the same action themselves. Mirror neurons fire when
observing an action and performing an action, indicating that these
neurons found in the motor cortex are necessary for understanding a
visual process.
The presence of mirror neurons may indicate that non-verbal, gestural
communication is far more ancient than previously thought to be. Motor
theory of speech perception relies on the understanding of motor
representations that underlie speech gestures, such as lip movement.
There is no clear understanding of speech perception currently, but it
is generally accepted that the motor cortex is activated in speech
perception to some capacity.
"Musilanguage"
The
term "musilanguage" (or "hmmmmm") refers to a pre-linguistic system of
vocal communication from which (according to some scholars) both music and
language later derived. The idea is that rhythmic, melodic, emotionally
expressive vocal ritual helped bond coalitions and, over time, set up
selection pressures for enhanced volitional control over the speech
articulators. Patterns of synchronized choral chanting are imagined to
have varied according to the occasion. For example, "we're setting off
to find honey" might sound qualitatively different from "we're setting
off to hunt" or "we're grieving over our relative's death". If social
standing depended on maintaining a regular beat and harmonizing one's
own voice with that of everyone else, group members would have come
under pressure to demonstrate their choral skills.
Archaeologist Steven Mithen
speculates that the Neanderthals possessed some such system, expressing
themselves in a "language" known as "Hmmmmm", standing for Holistic, manipulative, multi-modal, musical and mimetic. In Bruce Richman's earlier version of essentially the same idea,
frequent repetition of the same few songs by many voices made it easy
for people to remember those sequences as whole units. Activities that a
group of people were doing while they were vocalizing together —
activities that were important or striking or richly emotional — came to
be associated with particular sound sequences, so that each time a
fragment was heard, it evoked highly specific memories. The idea is that
the earliest lexical items (words) started out as abbreviated fragments
of what were originally communal songs.
"Whenever people sang or chanted a
particular sound sequence they would remember the concrete particulars
of the situation most strongly associated with it: ah, yes! we sing this
during this particular ritual admitting new members to the group; or,
we chant this during a long journey in the forest; or, when a clearing
is finished for a new camp, this is what we chant; or these are the
keenings we sing during ceremonies over dead members of our group."
— Richman,
B. 2000. How music fixed "nonsense" into significant formulas: on
rhythm, repetition, and meaning. In N. L. Wallin, B. Merker and S. Brown
(eds), The Origins of Music: An introduction to evolutionary musicology. Cambridge, Massachusetts: MIT Press, pp. 301-314.
As group members accumulated an expanding repertoire of songs for
different occasions, interpersonal call-and-response patterns evolved
along one trajectory to assume linguistic form. Meanwhile, along a
divergent trajectory, polyphonic singing and other kinds of music became
increasingly specialized and sophisticated.
To explain the establishment of syntactical speech, Richman cites
English "I wanna go home". He imagines this to have been learned in the
first instance not as a combinatorial sequence of free-standing words,
but as a single stuck-together combination — the melodic sound people
make to express "feeling homesick". Someone might sing "I wanna go
home", prompting other voices to chime in with "I need to go home", "I'd
love to go home", "Let's go home" and so forth. Note that one part of
the song remains constant, while another is permitted to vary. If this
theory is accepted, syntactically complex speech began evolving as each
chanted mantra allowed for variation at a certain point, allowing for
the insertion of an element from some other song. For example, while
mourning during a funeral rite, someone might want to recall a memory of
collecting honey with the deceased, signaling this at an appropriate
moment with a fragment of the "we're collecting honey" song. Imagine
that such practices became common. Meaning-laden utterances would now
have become subject to a distinctively linguistic creative principle —
that of recursive embedding.
Hunter-gatherer egalitarianism
Mbendjele hunter-gatherer meat sharing
Many scholars associate the evolutionary emergence of speech with
profound social, sexual, political and cultural developments. One view
is that primate-style dominance needed to give way to a more cooperative
and egalitarian lifestyle of the kind characteristic of modern
hunter-gatherers.
Intersubjectivity
According to Michael Tomasello, the key cognitive capacity distinguishing Homo sapiens from our ape cousins is "intersubjectivity". This entails turn-taking
and role-reversal: your partner strives to read your mind, you
simultaneously strive to read theirs, and each of you makes a conscious
effort to assist the other in the process. The outcome is that each
partner forms a representation of the other's mind in which their own
can be discerned by reflection.
Tomasello argues that this kind of bi-directional cognition is
central to the very possibility of linguistic communication. Drawing on
his research with both children and chimpanzees, he reports that human
infants, from one year old onwards, begin viewing their own mind as if
from the standpoint of others. He describes this as a cognitive
revolution. Chimpanzees, as they grow up, never undergo such a
revolution. The explanation, according to Tomasello, is that their
evolved psychology is adapted to a deeply competitive way of life.
Wild-living chimpanzees from despotic social hierarchies, most
interactions involving calculations of dominance and submission. An
adult chimp will strive to outwit its rivals by guessing at their
intentions while blocking them from reciprocating. Since bi-directional
intersubjective communication is impossible under such conditions, the
cognitive capacities necessary for language don't evolve.
Counter-dominance
In the scenario favoured by David Erdal and Andrew Whiten, primate-style dominance provoked equal and opposite coalitionary resistance — counter-dominance.
During the course of human evolution, increasingly effective strategies
of rebellion against dominant individuals led to a compromise. While
abandoning any attempt to dominate others, group members vigorously
asserted their personal autonomy, maintaining their alliances to make
potentially dominant individuals think twice. Within increasingly stable
coalitions, according to this perspective, status began to be earned in
novel ways, social rewards accruing to those perceived by their peers
as especially cooperative and self-aware.
Reverse dominance
While counter-dominance, according to this evolutionary narrative, culminates in a stalemate, anthropologist Christopher Boehm
extends the logic a step further. Counter-dominance tips over at last
into full-scale "reverse dominance". The rebellious coalition decisively
overthrows the figure of the primate alpha-male. No dominance is
allowed except that of the self-organized community as a whole.
As a result of this social and political change, hunter-gatherer
egalitarianism is established. As children grow up, they are motivated
by those around them to reverse perspective, engaging with other minds
on the model of their own. Selection pressures favor such psychological
innovations as imaginative empathy, joint attention, moral judgment,
project-oriented collaboration and the ability to evaluate one's own
behavior from the standpoint of others. Underpinning enhanced
probabilities of cultural transmission and cumulative cultural
evolution, these developments culminated in the establishment of
hunter-gatherer-style egalitarianism in association with intersubjective
communication and cognition. It is in this social and political context
that language evolves.
Scenarios involving mother-infant interactions
"Putting the baby down"
According
to Dean Falk's "putting the baby down" theory, vocal interactions
between early hominin mothers and infants sparked a sequence of events
that led, eventually, to our ancestors' earliest words.
The basic idea is that evolving human mothers, unlike their monkey and
ape counterparts, couldn't move around and forage with their infants
clinging onto their backs. Loss of fur in the human case left infants
with no means of clinging on. Frequently, therefore, mothers had to put
their babies down. As a result, these babies needed reassurance that
they were not being abandoned. Mothers responded by developing
"motherese" — an infant-directed communicative system embracing facial
expressions, body language, touching, patting, caressing, laughter,
tickling and emotionally expressive contact calls. The argument is that
language somehow developed out of all this.
- Criticism
While this theory may explain a certain kind of infant-directed
"protolanguage" — known today as "motherese" — it does little to solve
the really difficult problem, which is the emergence among adults of
syntactical speech.
Co-operative breeding
Evolutionary anthropologist Sarah Hrdy
observes that only human mothers among great apes are willing to let
another individual take hold of their own babies; further, we are
routinely willing to let others babysit. She identifies lack of trust as
the major factor preventing chimp, bonobo or gorilla mothers from doing
the same: "If ape mothers insist on carrying their babies
everywhere ... it is because the available alternatives are not safe
enough." The fundamental problem is that ape mothers (unlike monkey
mothers who may often babysit) do not have female relatives nearby. The
strong implication is that, in the course of Homo evolution, allocare could develop because Homo mothers did have female kin close by — in the first place, most reliably, their own mothers. Extending the Grandmother hypothesis, Hrdy argues that evolving Homo erectus
females necessarily relied on female kin initially; this novel
situation in ape evolution of mother, infant and mother's mother as
allocarer provided the evolutionary ground for the emergence of
intersubjectivity. She relates this onset of "cooperative breeding in an
ape" to shifts in life history and slower child development, linked to
the change in brain and body size from the 2 million year mark.
Primatologist Klaus Zuberbühler
uses these ideas to help explain the emergence of vocal flexibility in
the human species. Co-operative breeding would have compelled infants to
struggle actively to gain the attention of caregivers, not all of whom
would have been directly related. A basic primate repertoire of vocal
signals may have been insufficient for this social challenge. Natural
selection, according to this view, would have favored babies with
advanced vocal skills, beginning with babbling (which triggers positive
responses in care-givers) and paving the way for the elaborate and
unique speech abilities of modern humans.
Was "mama" the first word?
These
ideas might be linked to those of the renowned structural linguist
Roman Jakobson, who claimed that "the sucking activities of the child
are accompanied by a slight nasal murmur, the only phonation to be
produced when the lips are pressed to the mother's breast ... and the
mouth is full".
He proposed that later in the infant's development, "this phonatory
reaction to nursing is reproduced as an anticipatory signal at the mere
sight of food and finally as a manifestation of a desire to eat, or more
generally, as an expression of discontent and impatient longing for
missing food or absent nurser, and any ungranted wish." So, the action
of opening and shutting the mouth, combined with the production of a
nasal sound when the lips are closed, yielded the sound sequence "Mama",
which may, therefore, count as the very first word. Peter MacNeilage
sympathetically discusses this theory in his major book, The Origin of Speech, linking it with Dean Falk's "putting the baby down" theory (see above). Needless to say, other scholars have suggested completely different candidates for Homo sapiens' very first word.
Niche construction theory
A beaver dam in Tierra del Fuego. Beavers adapt to an environmental niche which they shape by their own activities.
While
the biological language faculty is genetically inherited, actual
languages or dialects are culturally transmitted, as are social norms,
technological traditions and so forth. Biologists expect a robust
co-evolutionary trajectory linking human genetic evolution with the
evolution of culture. Individuals capable of rudimentary forms of protolanguage would have
enjoyed enhanced access to cultural understandings, while these,
conveyed in ways that young brains could readily learn, would, in turn,
have become transmitted with increasing efficiency.
In some ways like beavers, as they construct their dams, humans have always engaged in niche construction,
creating novel environments to which they subsequently become adapted.
Selection pressures associated with prior niches tend to become relaxed
as humans depend increasingly on novel environments created continuously
by their own productive activities. According to Steven Pinker,
language is an adaptation to "the cognitive niche". Variations on the
theme of ritual/speech co-evolution — according to which speech evolved
for purposes of internal communication within a ritually constructed
domain — have attempted to specify more precisely when, why and how this
special niche was created by human collaborative activity.
Conceptual frameworks
Structuralism
"Consider
a knight in chess. Is the piece by itself an element of the game?
Certainly not. For as a material object, separated from its square on
the board and the other conditions of play, it is of no significance for
the player. It becomes a real, concrete element only when it takes on
or becomes identified with its value in the game. Suppose that during a
game this piece gets destroyed or lost. Can it be replaced? Of course,
it can. Not only by some other knight but even by an object of quite a
different shape, which can be counted as a knight, provided it is
assigned the same value as the missing piece."
— de Saussure, F. (1983) [1916]. Course in General Linguistics. Translated by R. Harris. London: Duckworth. pp. 108–09.
The Swiss scholar Ferdinand de Saussure
founded linguistics as a twentieth-century professional discipline.
Saussure regarded a language as a rule-governed system, much like a
board game such as chess. In order to understand chess, he insisted, we
must ignore such external factors as the weather prevailing during a
particular session or the material composition of this or that piece.
The game is autonomous with respect to its material embodiments. In the
same way, when studying language, it's essential to focus on its
internal structure as a social institution. External matters (e.g., the shape of the human tongue) are irrelevant from this standpoint. Saussure regarded 'speaking' (parole) as individual, ancillary and more or less accidental by comparison with "language" (langue), which he viewed as collective, systematic and essential.
Saussure showed little interest in Darwin's theory of evolution
by natural selection. Nor did he consider it worthwhile to speculate
about how language might originally have evolved. Saussure's assumptions
in fact cast doubt on the validity of narrowly conceived origins
scenarios. His structuralist paradigm, when accepted in its original
form, turns scholarly attention to a wider problem: how our species
acquired the capacity to establish social institutions in general.
Behaviourism
"The basic processes and relations
which give verbal behavior its special characteristics are now fairly
well understood. Much of the experimental work responsible for this
advance has been carried out on other species, but the results have
proved to be surprisingly free of species restrictions. Recent work has
shown that the methods can be extended to human behavior without serious
modification."
— Skinner, B.F. (1957). Verbal Behavior. New York: Appleton Century Crofts. p. 3.
In the United States, prior to and immediately following World War II, the dominant psychological paradigm was behaviourism. Within this conceptual framework, language was seen as a certain kind of behaviour — namely, verbal behavior,
to be studied much like any other kind of behavior in the animal world.
Rather as a laboratory rat learns how to find its way through an
artificial maze, so a human child learns the verbal behavior of the
society into which it is born. The phonological, grammatical and other
complexities of speech are in this sense "external" phenomena, inscribed
into an initially unstructured brain. Language's emergence in Homo sapiens,
from this perspective, presents no special theoretical challenge. Human
behavior, whether verbal or otherwise, illustrates the malleable nature
of the mammalian — and especially the human — brain.
Chomskyan Nativism
Nativism is the theory that humans are born with certain specialized cognitive modules enabling us to acquire highly complex bodies of knowledge such as the grammar of a language.
"There is a long history of
study of the origin of language, asking how it arose from calls of apes
and so forth. That investigation in my view is a complete waste of time
because language is based on an entirely different principle than any
animal communication system."
— Chomsky, N. (1988). Language and Problems of Knowledge. Cambridge, Massachusetts: MIT Press. p. 183.
From the mid-1950s onwards, Noam Chomsky, Jerry Fodor and others mounted what they conceptualized as a 'revolution' against behaviorism. Retrospectively, this became labelled 'the cognitive revolution'.
Whereas behaviorism had denied the scientific validity of the concept
of "mind", Chomsky replied that, in fact, the concept of "body" is more
problematic. Behaviourists tended to view the child's brain as a tabula rasa,
initially lacking structure or cognitive content. According to B. F.
Skinner, for example, richness of behavioral detail (whether verbal or
non-verbal) emanated from the environment. Chomsky turned this idea on
its head. The linguistic environment encountered by a young child,
according to Chomsky's version of psychological nativism,
is in fact hopelessly inadequate. No child could possibly acquire the
complexities of grammar from such an impoverished source.
Far from viewing language as wholly external, Chomsky re-conceptualized
it as wholly internal. To explain how a child so rapidly and
effortlessly acquires its natal language, he insisted, we must conclude
that it comes into the world with the essentials of grammar already
pre-installed.
No other species, according to Chomsky, is genetically equipped with a
language faculty — or indeed with anything remotely like one. The emergence of such a faculty in Homo sapiens, from this standpoint, presents biological science with a major theoretical challenge.
Speech act theory
One way to explain biological complexity is by reference to its inferred function. According to the influential philosopher John Austin, speech's primary function is active in the social world.
Speech acts,
according to this body of theory, can be analyzed on three different
levels: elocutionary, illocutionary and perlocutionary. An act is locutionary
when viewed as the production of certain linguistic sounds — for
example, practicing correct pronunciation in a foreign language. An act
is illocutionary insofar as it constitutes an intervention in the
world as jointly perceived or understood. Promising, marrying,
divorcing, declaring, stating, authorizing, announcing and so forth are
all speech acts in this illocutionary sense. An act is perlocutionary
when viewed in terms of its direct psychological effect on an audience.
Frightening a baby by saying 'Boo!' would be an example of a
"perlocutionary" act.
For Austin, "doing things" with words means, first and foremost, deploying illocutionary
force. The secret of this is community participation or collusion.
There must be a 'correct' (conventionally agreed) procedure, and all
those concerned must accept that it has been properly followed.
"One
of our examples was, for instance, the utterance 'I do' (take this
woman to be my lawful wedded wife), as uttered in the course of a
marriage ceremony. Here we should say that in saying these words we are doing something — namely, marrying, rather than reporting something, namely that we are marrying."
— Austin, J.L. (1962). How To Do Things With Words. Oxford: Oxford University Press. pp. 12–13.
In the case of a priest declaring a couple to be man and wife, his
words will have illocutionary force only if he is properly authorized
and only if the ceremony is properly conducted, using words deemed
appropriate to the occasion. Austin points out that should anyone
attempt to baptize a penguin, the act would be null and void. For
reasons which have nothing to do with physics, chemistry or biology,
baptism is inappropriate to be applied to penguins, irrespective of the
verbal formulation used.
This body of theory may have implications for speculative
scenarios concerning the origins of speech. "Doing things with words"
presupposes shared understandings and agreements pertaining not just to
language but to social conduct more generally. Apes might produce
sequences of structured sound, influencing one another in that way. To
deploy illocutionary force, however, they would need to have
entered a non-physical and non-biological realm — one of shared
contractual and other intangibles. This novel cognitive domain consists
of what philosophers term "institutional facts" — objective facts whose
existence, paradoxically, depends on communal faith or belief.
Few primatologists, evolutionary psychologists or anthropologists
consider that nonhuman primates are capable of the necessary levels of
joint attention, sustained commitment or collaboration in pursuit of
future goals.
Biosemiotics
"the deciphering of the genetic
code has revealed our possession of a language much older than
hieroglyphics, a language as old as life itself, a language that is the
most living language of all — even if its letters are invisible and its
words are buried in the cells of our bodies."
— Beadle, G.; Beadle, M. (1966). The Language of Life. An introduction to the science of genetics. New York: Doubleday and Co.
Biosemiotics is a relatively new discipline, inspired in large part
by the discovery of the genetic code in the early 1960s. Its basic
assumption is that Homo sapiens is not alone in its reliance on codes and signs. Language and symbolic culture must have biological roots, hence semiotic principles must apply also in the animal world.
The discovery of the molecular structure of DNA apparently
contradicted the idea that life could be explained, ultimately, in terms
of the fundamental laws of physics. The letters of the genetic alphabet
seemed to have "meaning", yet meaning is not a concept that has any
place in physics. The natural science community initially solved this
difficulty by invoking the concept of "information", treating
information as independent of meaning. But a different solution to the
puzzle was to recall that the laws of physics in themselves are never
sufficient to explain natural phenomena. To explain, say, the unique
physical and chemical characteristics of the planets in our solar
system, scientists must work out how the laws of physics became
constrained by particular sequences of events following the formation of
the Sun.
According to Howard Pattee,
the same principle applies to the evolution of life on earth, a process
in which certain "frozen accidents" or "natural constraints" have from
time to time drastically reduced the number of possible evolutionary
outcomes. Codes, when they prove to be stable over evolutionary time,
are constraints of this kind. The most fundamental such "frozen
accident" was the emergence of DNA as a self-replicating molecule, but
the history of life on earth has been characterized by a succession of
comparably dramatic events, each of which can be conceptualized as the
emergence of a new code. From this perspective, the evolutionary emergence of spoken language was one more event of essentially the same kind.
The Handicap principle
A peacock's tail: a classic example of costly signalling
In 1975, the Israeli theoretical biologist Amotz Zahavi
proposed a novel theory which, although controversial, has come to
dominate Darwinian thinking on how signals evolve. Zahavi's "handicap
principle" states that to be effective, signals must be reliable; to be
reliable, the bodily investment in them must be so high as to make
cheating unprofitable.
Paradoxically, if this logic is accepted, signals in nature
evolve not to be efficient but, on the contrary, to be elaborate and
wasteful of time and energy. A peacock's tail is the classic
illustration. Zahavi's theory is that since peahens are on the look-out
for male braggarts and cheats, they insist on a display of quality so
costly that only a genuinely fit peacock could afford to pay. Needless
to say, not all signals in the animal world are quite as elaborate as a
peacock's tail. But if Zahavi is correct, all require some bodily
investment — an expenditure of time and energy which "handicaps" the
signaller in some way.
Animal vocalizations (according to Zahavi) are reliable because
they are faithful reflections of the state of the signaller's body. To
switch from an honest to a deceitful call, the animal would have to
adopt a different bodily posture. Since every bodily action has its own
optimal starting position, changing that position to produce a false
message would interfere with the task of carrying out the action really
intended. The gains made by cheating would not make up for the losses
incurred by assuming an improper posture — and so the phony message
turns out to be not worth its price.
This may explain, in particular, why ape and monkey vocal signals have
evolved to be so strikingly inflexible when compared with the varied
speech sounds produced by the human tongue. The apparent inflexibility
of chimpanzee vocalizations may strike the human observer as surprising
until we realize that being inflexible is necessarily bound up with
being perceptibly honest in the sense of "hard-to-fake".
If we accept this theory, the emergence of speech becomes
theoretically impossible. Communication of this kind just cannot evolve.
The problem is that words are cheap. Nothing about their acoustic
features can reassure listeners that they are genuine and not fakes. Any
strategy of reliance on someone else's tongue — perhaps the most
flexible organ in the body — presupposes unprecedented levels of honesty
and trust. To date, Darwinian thinkers have found it difficult to
explain the requisite levels of community-wide cooperation and trust.
An influential standard textbook is Animal Signals, by John Maynard Smith and David Harper.
These authors divide the costs of communication into two components,
(1) the investment necessary to ensure transmission of a discernible
signal; (2) the investment necessary to guarantee that each signal is
reliable and not a fake. The authors point out that although costs in
the second category may be relatively low, they are not zero. Even in
relatively relaxed, cooperative social contexts — for example, when
communication is occurring between genetic kin — some investment must be
made to guarantee reliability. In short, the notion of super-efficient
communication — eliminating all costs except those necessary for
successful transmission — is biologically unrealistic. Yet speech comes
precisely into this category.
Johnstone's 1997 representation of the Handicap Principle.
The graph shows the different signal intensities as a result of costs
and benefits. If two individuals face different costs but have the same
benefits, or have different benefits but the same cost, they will
signal at different levels. The higher the signal represents a more
reliable quality. The high-quality individual will maximize costs
relative to benefits at a high signal intensities, while the low-quality
individual maximizes their benefits relative to cost at low signal
intensity. The high-quality individual is shown to take more risks
(greater cost), which can be understood in terms of honest signals,
which are expensive. The stronger you are, the more easily you can bare
the cost of the signal, making you a more appealing mating partner. The
low-quality individuals are less likely to be able to afford a specific
signal, and will consequently be less likely to attract a mate.
Cognitive linguistics
Cognitive
linguistics views linguistic structure as arising continuously out of
usage. Speakers are forever discovering new ways to convey meanings by
producing sounds, and in some cases, these novel strategies become
conventionalized. Between the phonological structure and semantic
structure, there is no causal relationship. Instead, each novel pairing
of sound and meaning involves an imaginative leap.
In their book, Metaphors We Live By, George Lakoff and Mark Johnson helped pioneer this approach, claiming that metaphor is what makes human thought special. All language, they argued, is permeated with metaphor, whose use in fact constitutes
distinctively human — that is, distinctively abstract — thought. To
conceptualize things which cannot be directly perceived — intangibles
such as time, life, reason, mind, society or justice — we have no choice
but to set out from more concrete and directly perceptible phenomena
such as motion, location, distance, size and so forth. In all cultures
across the world, according to Lakoff and Johnson, people resort to such
familiar metaphors as ideas are locations, thinking is moving and mind is body.
For example, we might express the idea of "arriving at a crucial point
in our argument" by proceeding as if literally traveling from one
physical location to the next.
Metaphors, by definition, are not literally true. Strictly
speaking, they are fictions — from a pedantic standpoint, even
falsehoods. But if we couldn't resort to metaphorical fictions, it's
doubtful whether we could even form conceptual representations of such
nebulous phenomena as "ideas", thoughts", "minds", and so forth.
The bearing of these ideas on current thinking on speech origins
remains unclear. One suggestion is that ape communication tends to
resist the metaphor for social reasons. Since they inhabit a Darwinian
(as opposed to morally regulated) social world, these animals are under
strong competitive pressure not to accept patent fictions as
valid communicative currency. Ape vocal communication tends to be
inflexible, marginalizing the ultra-flexible tongue, precisely because
listeners treat with suspicion any signal which might prove to be a
fake. Such insistence on perceptible veracity is clearly incompatible
with metaphoric usage. An implication is that neither articulate speech
nor distinctively human abstract thought could have begun evolving until
our ancestors had become more cooperative and trusting of one another's
communicative intentions.
Natural science vs social science interpretations
Social reality
When people converse with one another, according to the American philosopher John Searle,
they're making moves, not in the real world which other species
inhabit, but in a shared virtual realm peculiar to ourselves. Unlike the
deployment of muscular effort to move a physical object, the deployment
of illocutionary force
requires no physical effort (except the movement of the tongue/mouth to
produce speech) and produces no effect which any measuring device could
detect. Instead, our action takes place on a quite different level —
that of social reality. This kind of reality is in one sense
hallucinatory, being a product of collective intentionality. It
consists, not of "brute facts" — facts which exist anyway, irrespective
of anyone's belief — but of "institutional facts", which "exist" only if
you believe in them. Government, marriage, citizenship and money are
examples of "institutional facts". One can distinguish between "brute"
facts and "institutional" ones by applying a simple test. Suppose no one
believed in the fact — would it still be true? If the answer is "yes",
it's "brute". If the answer is "no", it's "institutional".
"Imagine a group of primitive
creatures, more or less like ourselves ... Now imagine that acting as a
group, they build a barrier, a wall around the place where they live ...
The wall is designed to keep intruders out and keep members of the
group in ... Let us suppose that the wall gradually decays. It slowly
deteriorates until all that is left is a line of stones. But let us
suppose that the inhabitants continue to treat the line of stones as if
it could perform the function of the wall. Let us suppose that, as a
matter of fact, they treat the line of stones just as if they understood
that it was not to be crossed ... This shift is the decisive move in
the creation of institutional reality. It is nothing less than the
decisive move in the creation of what we think of as distinctive in
humans, as opposed to animals, societies."
— John R. Searle (1995). The construction of social reality. Free Press. p. 134.
The facts of language in general and of speech, in particular, are,
from this perspective, "institutional" rather than "brute". The semantic
meaning of a word, for example, is whatever its users imagine it to be.
To "do things with words" is to operate in a virtual world which seems
real because we share it in common. In this incorporeal world, the laws
of physics, chemistry, and biology do not apply. That explains why
illocutionary force can be deployed without exerting muscular effort.
Apes and monkeys inhabit the "brute" world. To make an impact, they must
scream, bark, threaten, seduce or in other ways invest bodily effort.
If they were invited to play chess, they would be unable to resist
throwing their pieces at one another. Speech is not like that. A few
movements of the tongue, under appropriate conditions, can be sufficient
to open parliament, annul a marriage, confer a knighthood or declare
war. To explain, on a Darwinian basis, how such apparent magic first began to work, we must ask how, when and why Homo sapiens succeeded in establishing the wider domain of institutional facts.
Nature or society?
"Brute facts", in the terminology of speech act philosopher John Searle,
are facts which are true anyway, regardless of human belief. Suppose
you don't believe in gravity: jump over a cliff and you'll still fall. Natural science is the study of facts of this kind. "Institutional facts" are fictions accorded factual status within human social institutions.
Monetary and commercial facts are fictions of this kind. The
complexities of today's global currency system are facts only while we
believe in them: suspend the belief and the facts correspondingly
dissolve. Yet although institutional facts rest on human belief, that
doesn't make them mere distortions or hallucinations. Take my confidence
that these two five-pound banknotes in my pocket are worth ten pounds.
That's not merely my subjective belief: it's an objective, indisputable
fact. But now imagine a collapse of public confidence in the currency
system. Suddenly, the realities in my pocket dissolve.
Scholars who doubt the scientific validity of the notion of "institutional facts" include Noam Chomsky,
for whom language is not social. In Chomsky's view, language is a
natural object (a component of the individual brain) and its study,
therefore, a branch of natural science. In explaining the origin of
language, scholars in this intellectual camp invoke non-social
developments — in Chomsky's case, a random genetic mutation.
Chomsky argues that language might exist inside the brain of a single
mutant gorilla even if no one else believed in it, even if no one else
existed apart from the mutant — and even if the gorilla in question
remained unaware of its existence, never actually speaking. In the opposite philosophical camp are those who, in the tradition of Ferdinand de Saussure,
argue that if no one believed in words or rules, they simply would not
exist. These scholars, correspondingly, regard language as essentially
institutional, concluding that linguistics should be considered a topic
within social science.
In explaining the evolutionary emergence of language, scholars in this
intellectual camp tend to invoke profound changes in social
relationships.
Criticism. Darwinian scientists today see little value in the traditional distinction between "natural" and "social" science. Darwinism in its modern form is the study of cooperation and competition in nature — a topic which is intrinsically social.
Against this background, there is an increasing awareness among
evolutionary linguists and Darwinian anthropologists that traditional
inter-disciplinary barriers can have damaging consequences for
investigations into the origins of speech.
