my dissertation
TRANSCRIPT
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Actions speak louder than words?
Examining the Evidence for a gestural genesis of human language.
Student ID: 200604286
Supervisor: Dr. Diane Nelson
Ling 3200 – Linguistics Dissertation
Word Count: 11,067
The University of Leeds, 29th April 2015
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Abstract The prevailing theory in language emergence is that it developed vocally, either in a
continuous fashion from the calls of early primates, or discontinuously as the result of
a tremendous genetic occurrence that endowed our forefathers with the gift of
language. However, in this dissertation I examine an alternative, and I believe more
plausible, possibility that language emerged first from a system of gestures. Using
evidence from a combination of primate studies, neurolinguistics, child language and
sign languages, I form a picture of language evolution that builds upon the cognitive
and linguistic capacities of extant ape species, the capacities of which are assumed to
have been present in the last common ancestor of humans and apes. This begins with
early bipedal hominids using their now freed hands to use iconic gestures to shape
and describe the world around them, leading to a proto-‐language-‐like capacity based
on manual gestures, before speech assumed dominance perhaps as late as the
emergence of Homo sapiens and the ‘human revolution’ 35,000-‐100,000 years ago.
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Table of Contents LIST OF FIGURES .............................................................................................................................. 4 1. INTRODUCTION ........................................................................................................................... 5 2. PRIMATE STUDIES ...................................................................................................................... 8 2.1 VOCAL CONTROL VS. MANUAL CONTROL .............................................................................................. 8 2.2 PAN ............................................................................................................................................................... 9 2.3 PRIMATE LANGUAGE EXPERIMENTS .................................................................................................... 12 2.3.1 Washoe the Signing Chimpanzee ............................................................................................. 12 2.3.2 Kanzi’s Keyboard ............................................................................................................................ 13 2.3.3 A Critical Period for Ape Language? ...................................................................................... 14
3. THE BRAIN .................................................................................................................................. 15 3.1 MIRROR NEURONS AND BROCA’S AREA .............................................................................................. 15 3.1.1 Reflections on Mirror Neurons and Theory of Mind ........................................................ 17
3.2 THE MOTOR THEORY OF SPEECH PERCEPTION ................................................................................. 18 3.3 BIPEDALISM AND BRAIN GROWTH ....................................................................................................... 19 3.4 ADAPTATIONS FOR SPEECH – A MODERN PHENOMENON? ............................................................. 20 3.4.1 Changes to Anatomy – Speech Came Later ......................................................................... 20 3.4.2 The Hypoglossal Canal, Articulation and Breathing Control ...................................... 22 3.4.3 FOXP2 ................................................................................................................................................... 22
4. SIGN LANGUAGE ........................................................................................................................ 23 4.1 LATERALISATION OF LANGUAGE AND HANDEDNESS ........................................................................ 24 4.2 CHILD LANGUAGE ..................................................................................................................................... 25 4.2.1 Manual Babbling ............................................................................................................................. 26 4.2.2 Children’s Gestures ......................................................................................................................... 26
4.3 NOVEL SIGN LANGUAGES ........................................................................................................................ 27 4.3.1 Homesign in Deaf Children ......................................................................................................... 28 4.3.2 Nicaraguan Sign Language, (LSN) and Idioma de Signos Nicaragünese (ISN) .. 29 4.3.3 Al-‐Sayyid Bedouin Sign Language (ABSL) ........................................................................... 30 4.3.4 Creating a New Communication System from Scratch .................................................. 31
5. BUT WHY THE SWITCH TO SPEECH? .................................................................................. 34 6. CONCLUSION .............................................................................................................................. 36 7. REFERENCES ............................................................................................................................... 38
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List of Figures
Fig. 1 Phylogenetic tree of extant great ape species………………………………………………….9
Fig. 2 Flexibility of different communication types in chimpanzees and bonobos….…11
Fig. 3 A comparison of the macaque and human cerebral cortex…………………………….16
Fig. 4 Brain size comparison of extant primates and other species………………………….20
Fig. 5 Comparing the human and chimpanzee vocal tract………………..……………………..21
Fig. 6 Frequency of interaction type in chimpanzees and bonobos…………………………..32
Fig. 7 Success of different gesture types judged by identification accuracy……………..32
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1. Introduction Ever since scientists and thinkers began to doubt the traditional, religious stance on
language as a gift from God, scattered from the mythical Tower of Babel to form the
world’s myriad tongues, language’s origin has enthralled and perplexed generations.
Among them are proponents of the gesture-‐first theory, who have put forward the
idea in various guises since John Bulwer’s ‘The Natural Language of the Hand’ (1644),
before Cordemoy (1668/1972:3) called gestures ‘the most natural way to express our
thoughts... also the first of all the languages,’ citing its ubiquitous understanding
across countries and cultures as a reason for its feasibility. The 18th century
philosopher Giambattista Vico (1953/1744) imagined an original system of mimetic
gestures which represented images of the imagination, before de Condillac
(1971/1746) proposed a similar idea demonstrated by a fable of two strangers
communicating by sign alone. The 19th century saw Darwin haltingly acknowledge
that language in its original form was perhaps ‘aided by signs and gestures’ (Darwin,
1871:86). However, this speculation was not well received by bodies in both France
and England. The Linguistics Society of Paris, founded in 1865, banned from the
outset all debates that focused on the origin of language, and in 1873 the President of
the Philological Society admonished: ‘We shall do more by tracing the development of
one work-‐a-‐day tongue, than by filling waste-‐paper baskets by reams of paper
covered with speculations on the origins of all tongues.’ (McNeill, 2005:11).
Despite its troubled beginnings, the gestural theory picked up speed in the
20th century with the publication of Gordon Hewes’ ‘Primate Communication and the
Gestural Origin of Language’ (1973) in which he sets forth his argument with evidence
from recently conducted primate language experiments. Using more modern
technology, Rizzolatti et al (1998) published a paper describing the presence and
importance of mirror neurons in certain areas of the brain. Their hypothesis provides
support for the gestural origin theory as it evidences a strong relationship between
action of the arm and mouth in non-‐human primates, as well as a crucial role in
seeing and mimicking the actions of others (to be discussed in more detail in 3.1). This
paved the way for other linguists to further examine its merit, notably Corballis (2002,
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2003, 2012), Armstrong & Wilcox (1995, 2007), Pollick & de Waal (2007) and
Tomasello (2008).
Proponents of the vocal theory argue that language evolved not from signs
but from a system evolved in the auditory-‐vocal modality (Dunbar 1996; Deacon
1997; Fitch 2000; Knight 2008). The literature on the speech-‐first argument focuses
on either a discontinuous view that language arose suddenly and in a near-‐perfect
form, perhaps by the appearance of a new gene (FOXP2) coinciding with the ‘human
revolution’ some 40,000 years ago (Chomsky, 1996, 2004; Lenneberg, 1967), or by a
continuous evolutionary process in a similar way to other adapted-‐for traits (Pinker
and Bloom, 1990).
New evidence collected over the past few decades bolsters the argument that
the speech-‐first scenario is inferior: the FOXP2 gene has recently been shown to have
existed in Neanderthals and has also been seen to influence both language processing
and motor sequencing ability, including finger movements (Peter et al, 2011), giving
compelling evidence that this gene may have had an influence in a gestural precursor
to language. The idea that language arose fully formed is also flawed. As Kirby
(2007:674) argues, ‘this is only really plausible if language isn’t as complex as it
appears. The appearance of eyes fully formed in evolution in one step is implausible
precisely because the eye is a complex organ’. Furthermore those who suggest that
language could have evolved from the vocal calls of non-‐human primates (Aiello &
Dunbar, 1993; Dunbar, 1996; Zuberbühler, 2005) do not account for the fact that
these vocalisations are inflexible and cannot be broken down or combined into
sequences, and that these calls are primarily instinctive and emotionally-‐driven:
‘production of sound in the absence of the appropriate emotional state seems to be
an almost impossible task for a chimpanzee’ notes eminent primatologist Jane
Goodall (1986:125). Despite a recent study of putty-‐nosed monkeys that claimed they
combine sounds to encode slightly different meanings, the compositional, recursive
power of human language was still lacking (Arnold & Zuberbühler 2006). However,
this basic combinatorial ability that seems to be present in these primates could signal
a rudimentary precursor to a complex aptitude for syntax that may well have been
present in the last common ancestor (‘LCA’ hereafter) (Fay et al, 2014; Cheney &
Seyfarth, 2005). A final objection to the theory is that if gesture was the first way in
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which language was used, then why do we now exclusively use speech to
communicate? MacNeilage suggests that a gestural system ‘would have proved so
indispensable that we would never have abandoned it’ (2011: 434), however there
are several advantages that signed languages provide, as well as other reasons as to
why a switch to a vocal modality could have occurred.
Instinctively, the iconic nature of the majority of signs lends itself better to the
earliest form of language; by describing the world around them iconically and
mimetically, our early bipedal ancestors gained the ability to transfer meaning from
one member of the group to another without the use of speech. As Stokoe (2001:xii)
puts it, ‘who could possibly have told the first speakers what the sounds they
produced were supposed to mean[?]’. He argues that the earliest communicative
system was based on gestures, where hand shapes represented aspects of the visual
world around our early ancestors: people, places, things, and the movements of the
hands represented actions and changes, and that these were the earliest form of
sentences: ‘The key to this development is that only gesture use could have initiated
syntax, a necessary feature of language.’ (2001:xiii)
In order to examine the support for the gestural theory of language evolution,
it is useful to turn to Bickerton’s three aspects of linguistic behaviour that he terms
‘living fossils’ (1990:105; 1995) of an earlier protolanguage. These consist of (i) the
Language of Trained Apes, (ii) Child Language and (iii) Pidgin Communication.
Although Bickerton is a speech-‐first advocate, he comments that ‘what form of signal
was first used is relatively unimportant’ (1990:156), and adapting his model to
examine the viability of the gestural equivalents instead of speech in language
evolution can provide clues to how language may have emerged gesturally. Since
evidence for the gesture theory has broadly been taken from a combination of
primate language studies, analysis of child language development and aspects of
pidgin sign language (such as Nicaraguan Sign Language), Bickerton’s model applies
perfectly to a gestural protolanguage. This evidence, combined with an examination
of language in the brain -‐ including the action of mirror neurons-‐ will be the focus of
this dissertation; the strength of each of these lines of inquiry will be evaluated in an
attempt to answer the question: did language emerge gesturally in our ancestors?
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2. Primate Studies
Since no animal in the wild has ever acquired the command of anything approaching
human language, it could seem unlikely to turn to this source of evidence to attempt
to explain it. However some linguists argue that by examining the abilities and
shortcomings of primate communication, the capabilities of the LCA can be
elucidated (Rizolatti & Arbib, 1998). This means it is possible to track the
development of traits necessary for fully articulate language through the Homo line
that were not present in our cousins’ lineage over the last ~8 million years of
evolution (Pinker, 2003).
2.1 Vocal Control vs. Manual Control Theories in support of the gesture-‐first argument have focused on the inability of
apes to control their vocalisations, compared to the ‘excellent cortical control over
the hands and arms’ (Corballis, 2009:22) that nonhuman primates demonstrate. In
primates, vocalisations lack the range and combinatorial power of human speech, and
are controlled by the limbic system, an ancient area of the brain associated with
emotion, and are not under the voluntary control of the motor cortex (Ploog 2002;
Fogassi & Ferrari, 2007). These primate vocalisations are primarily a reaction to a
specific emotion or need, such as fear, hunger or sexual desire (Deacon, 1997), and
have their evolutionary human counterparts in primal sounds like moaning, crying
and screaming (Pinker, 1994). This is in comparison to a large range of voluntary
manual movements, which are under the control of the lateral motor cortex and are
used flexibly (Hurford, 2003; Corballis, 2009), a skill that has been utilised in primate
language experiments (Gardner & Gardner, 1969; Savage-‐Rambaugh et al, 1998).
Further, both humans and nonhuman primates are primarily visual creatures,
with sight superior to hearing in both species, perhaps an evolutionary adaptation to
visual predation. This means that they are better adapted for communication in the
visual modality than the auditory (Corballis, 2010), and thus early hominids may have
had the tools to communicate using gesture before speech.
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2.2 Pan
Many animals in the wild commonly communicate with vocal calls, but the manual
gestures of humans and apes are considered practically unique (Maestripieri 2005;
Pollick & de Waal, 2007; Roberts et al, 2012). Hobaiter & Byrne (2014) argue that ape
gestures often have specific meanings and that captive and wild gorillas and
chimpanzees use intentional signs to serve specific functions. These flexible,
intentional gestures of the hands and limbs provide evidence of an ancestral trait
common to Homo sapiens and our great ape relatives that support the gestural
theory of language evolution (Roberts et al, 2012; Pika et al, 2005; Pollick & de Waal,
2007). The studies below demonstrate how language-‐trained, wild, and captive apes
help to elucidate the gestural theory of language evolution.
The phylogenetic tree below displays the relationship between extant great
apes and humans, and is consistent with the general estimate that the Pan line
separated from the Homo line around 5-‐7 million years ago (Kumar et al, 2005).
While all primates exhibit facial expressions and vocalisations, apes and
monkeys differ in that monkeys lack the free, ritualised hand gestures that are
present in chimpanzees and bonobos, which include begging for food with an
Figure 1. Phylogenetic tree of extant great ape species (www-‐tc.pbs.org)
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upturned palm, impatient wrist shaking, and domineering arm movements over a
subservient conspecific (Pollick et al, 2008).
Since bonobos and chimpanzees split from the Homo line the most recently,
they are the most closely related primates to human beings and the evolutionary
ancestry we share may shed light on the kind of abilities present in the LCA of humans
and apes, and therefore on how language may have evolved in our species (Corballis,
2009). Manual gestures have become of particular interest as the neural structures
associated with them in great apes are homologous with those associated with
language in the human brain (Roberts et al, 2013) (examined further in 3). Using this
logic, Pollick and de Waal (2007) ran a study to compare the flexibility of chimpanzee
and bonobo manual gestures with orofacial movements and vocalisations. The aim of
the study was to assess how context-‐driven these were, and to what extent gestures
were more flexible than vocalisations. They observed two groups of bonobos and two
groups of chimpanzees in captive environments, all of which exhibited aspects of
gesture, broadly defined by Kendon (2004:14) as ‘movements that… manifest
deliberate expressiveness to an obvious degree’. By this he means that to qualify as a
gesture, it must be meaningful, intentional and easily discerned by the audience
(Zlatev, 2015).
Firstly they found that gestures were far more flexible than either facial or
vocal signals, in that they were less bound to being produced in a particular context.
Corballis (2009:554) asserts that ‘freedom from context is one of the characteristics
of language’, and it is with this in mind that Pollick & de Waal enacted their study:
they calculated the ‘CTI’, or Context-‐Tie Index, which was the percentage of times
that a signal was used in its most typical social context, e.g. during grooming, to
initiate sex, etc. Fig. 2 shows that the vocalisations ‘scream’ and ‘pant hoot’ had a
very high correlation across contexts, meaning that they were produced far more
commonly in their typical contexts in comparison to gestures, which did not reach a
high CTI. Strikingly, four of the gestures correlated negatively across contexts,
suggesting that they are used in vastly different contexts by both the bonobo and
chimpanzee groups (Pollick & de Waal, 2007).
This discrepancy between species acts as further evidence that human
language may have its roots in the abilities of our primate cousins; their gestures vary
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between species just as human gestures vary across cultures as a result of cultural
transmission. In addition, human facial expressions tend to be far more universal than
culture-‐specific gestures (Kendon, 1995), and apes also tend to share facial
movements, evinced by the high CTI ‘silent bared teeth’ and ‘relaxed open mouth’
that is shared between chimps and bonobos (Fig. 2).
A comparable study conducted by Roberts et al (2012:466) garnered similar
results; they studied a wild population of chimpanzees and found that their gestures
‘are perceived semantically and manipulate the recipient’s movements and attention,
while recipients also infer the broader goal of the signaller from context.’
Overall gestures show greater contextual variation in both wild and captive
chimpanzees than facial and vocal signals, and do not necessarily need to be viewed
in a particular context to elicit a response unlike vocalisations, which are closely tied
to context. De Waal and Pollick (2012) argue that this makes gesture a likely
candidate for the modality in which symbolic meaning may have evolved in the early
hominid population.
Figure 2: Flexibility of different communication types in chimpanzees and bonobos, taken from Pollick & de Waal (2007: 8187).
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2.3 Primate Language Experiments The language of trained apes is one of Bickerton’s (1990:105) ‘living fossils’, aspects of
language that share some -‐ but not all-‐ of the characteristics of modern human
language. Tallerman argues that language trained apes such as those described below
likely show ‘the type of cognition early hominins brought to protolanguage’ (2011:
489), and thus can illuminate the aspects of cognition that were built upon to develop
language.
2.3.1 Washoe the Signing Chimpanzee There have been many attempts to teach primates language that have largely focused
on our closest relatives, chimps and bonobos (Gardner & Gardner 1969; Savage-‐
Rumbaugh et al, 1998). These experiments have shown that nonhuman primates
have no ability to speak whatsoever, having been inhibited by the shape of their vocal
tract -‐ the larynx is descended in humans, and the greater flexibility of our tongue
allows us to produce a larger array of sounds (Gillespie-‐Lynch et al, 2014). Voluntary
cortical command over their vocalisations is also limited, and is controlled largely by
the ‘cingulate system’, an area deep in the brain associated with emotion that is not
homologous with language areas (Vilain et al, 2011). Tellingly, attempts to teach
primates signed language have been far more successful.
Washoe the chimpanzee was adopted by the Gardners at ten months and was
raised by them as though she were a human child. She was taught a variety of signs in
simple ASL (American Sign Language) through imitation as well as by instruction. She
achieved a degree of proficiency in ASL beyond any vocal ability that was
demonstrated (Gardner & Gardner, 1969), and after 8 years had a repertoire of over
150 signs. Importantly she also displayed some ability at creating spontaneous signs,
notably combining the signs for ‘water’ and ‘bird’ when viewing a swan, as well as
‘rock berry’ for a brazil nut (Fouts, 1975; Fouts & Rigby, 1977). This kind of
spontaneous combination of gestures to create a novel sign was taken as evidence
that Washoe understood the meanings of the signs, and was not simply producing
them in response to specific stimuli.
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Furthermore, a secondary experiment exposed Washoe’s adopted son Loulis
exclusively to the sign language of four signing chimps (including Washoe), and found
that he actively learnt the signs through teaching as well as by the moulding of his
hands to the correct configuration (Fouts et al, 1989). This mirrors the mother-‐child
interaction, imitation and pedagogy prerequisite in human language acquisition.
2.3.2 Kanzi’s Keyboard Kanzi is considered the most accomplished of all the language-‐trained apes (Savage-‐
Rumbaugh et al, 1998; Corballis, 2012a) and communicates by pointing to a keyboard
with a range of lexigrams, as well as with some ASL. He was present while the
researchers attempted to teach his mother to use the lexical board to no success, and
acquired the ability spontaneously without implicit teaching or rewards (Savage-‐
Rumbaugh et al, 1986). Kanzi used the keyboard to string together combinations of
two or three symbols to create simple phrases, as well as inventing his own gestures
to add to his repertoire when he outstripped the 300 symbols available to him on the
lexical board. The keyboard required fine control to operate, and he also combined
pointing with other gestures to elucidate meaning. The combinations he put together
showed some capacity for English word order, as well as basic ability to assign
grammatical rules (Greenfield & Savage-‐Rumbaugh, 1990).
Strikingly, Kanzi’s ability to perceive human speech was more developed than
his production, and he frequently acted on complex, novel sentences even when the
requests were unusual or counterintuitive. For example, using toy equivalents he
correctly performed ‘make the doggie bite the snake’, as well as completing the task
with the animals’ roles reversed (Savage-‐Rumbaugh et al, 1993: 96). His
comprehension was compared to that of Alia, a human child at a similar age of
linguistic development, and was found to outstrip hers when tested on a variety of
sentence types. Kanzi responded correctly on 74% of occasions compared to Alia’s
65% (Savage-‐Rumbaugh et al, 1993:76). While Savage-‐Rumbaugh argues that ‘more
than any previous ape, the nature and the scope of Kanzi's language acquisition has
paralleled that of the human child’ (1993: 12). This is not to say that Kanzi displayed
human levels of intelligence, or even an extraordinary aptitude for human language.
His production was limited to simple phrases and requests, and showed little of the
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boundless expression that children express a little later in their development. Further,
96% of his ‘utterances’ were requests, a far larger percentage than would be normal
for a human child. Towards the end of the study Alia’s production and comprehension
leapt far beyond Kanzi’s (1993:567). This suggests that Kanzi’s abilities, although
impressive, are limited, and they resemble a large lexicon coupled with a very basic
‘proto-‐grammar’ that is not akin to human language (Pinker, 1994; Tallerman, 2011;
Fitch, 2010, who argues that this is no more than word order) and a good perception
of complex strings of lexical items. However there is little evidence to suggest that he
truly understands the more complex grammar that he hears. Tallerman (2011: 453)
provides the example ‘Go get the balloon that’s in the microwave’-‐ and argues that
there is no way of telling that Kanzi understands the relative clause and is instead
acting on the basic lexical items in the phrase ‘get – balloon – microwave’, and infers
the rest from context. This type of processing, a kind of telegraphic connecting of
gestures with basic understanding of objects and actions without complex grammar
in the manual mode, seems the most likely candidate to have been a precursor for
language in the LCA and early hominids.
2.3.3 A Critical Period for Ape Language? A largely under-‐addressed finding from the study was that of the nine apes that were
reared together, those who were not exposed to language until after the age of 2½
did not acquire the use of signs without prolonged, explicit language training
(Rumbaugh, 1977; Savage-‐Rumbaugh et al, 1993). Their comprehension too was
greatly diminished, and by 9 years of age the late-‐exposed apes only understood a
few words compared to the early-‐exposed chimps that all understood at least 40
different spoken words by 2½ years. The fact that humans also have a critical window
for language acquisition (Penfield & Roberts, 1959; Lenneberg, 1967) strengthens the
gesture-‐first argument in that humans and apes share similar neural traits, such as
brain plasticity in language learning, which may therefore have been present in the
LCA. It also weakens the musical protolanguage theory (Mithen, 2011), as human
song transmission has no such critical period (Tallerman, 2007).
While these attempts at teaching and monitoring apes’ language have been
somewhat successful, their actual language ability has barely progressed past the
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capability of a 2½-‐year-‐old girl. There is no doubt that apes can assign meaning to a
sign in hundreds of pairs (Fitch 2010), but the real merit in these studies is that they
show that the more likely scenario for language emergence is that it was based on a
system of manual gestures rather than vocalisations. They demonstrate an ability to
assign a symbol to a real-‐world referent in the manual domain, as well as a capacity
for a ‘proto-‐grammar’ (Greenfield & Savage-‐Rumbaugh, 1990: 572) in the perception
of basic syntax. Further, they show that ape gestures are susceptible to both social
learning and the attentional state of the recipient, which are both prerequisites for
language (Corballis, 2009). ‘Communicative capacities observed across members of a
clade (sibling species with a common ancestor, such as humans, chimpanzees, and
bonobos) are likely inherited from a common ancestor’ (Gillespie-‐Lynch et al, 2014:2).
Hence, these abilities are likely to be present in the LCA and our hominin ancestors
were likely to have been better preadapted for control of limbs and hand movements
than for vocal control. This was shown by the success of our great ape relatives in
types of sign language learning, as well as the greater flexibility of gesture in
communication than vocal calls.
3. The Brain I have described the likely cognitive and linguistic capabilities of our hominid
ancestors, as well as the similarities and differences between the Homo and Pan
branch of the Hominidae. The following is an examination of the brain’s role in
language and its evolution, and specifically how the visuo-‐manual modality was
crucial in the emergence and evolution of language. By studying both the human and
nonhuman primate brain in tandem, as well as the varying brain structures and
capacities of modern and ancient humans, a picture of how gesture could have been
the origin of language is elucidated.
3.1 Mirror Neurons and Broca’s Area At the simplest level, in order for language to evolve it is crucial that a sender and
receiver of a message are both able to produce and perceive a signal. Rizzolatti &
Craighero (2004:183) argue that mirror neurons are central in the development of
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this ability: ‘Mirror neurons represent the neural basis of a mechanism that creates a
direct link between the sender of a message and its receiver…actions done by other
individuals become messages that are understood by an observer without any
cognitive mediation.’ Thus, mirror neurons have provided a fresh perspective on the
gesture theory. First observed in macaques (Rizzolatti et al, 1998), and further
elaborated in the discovery of a mirror system (Arbib, 2005a; Rizzolatti & Sinigaglia,
2008), these are motor neurons that fire both when an animal performs an action as
well as when it is observed.
Although mirror neurons cannot be observed directly in the human brain
(Corballis, 2010), imaging has revealed a mirror-‐neuron system in humans that also
activates when actions are imitated, that is not present in monkeys (Rizzolatti,
Fogassi, & Gallese, 2001, Rizzolatti & Craighero, 2004). This has implications for the
evolution of language in that the ability to actively mimic another’s action would have
been pivotal in learning and propagating an emerging gestural system.
Further, the mirror neurons were found in an area of the macaque brain that
is homologous with Broca’s area in humans, the area traditionally associated with
language production (Fig. 3) (Broca, 1861; Fogassi and Ferrari, 2007). While Broca’s
area has traditionally been associated with the production of speech, it is also
involved in motor tasks such as complex finger and hand movements, sensorimotor
learning and imitating hand shapes (Rizzolatti & Craighero, 2004). This same
activation is also observed when people imagine themselves making these
movements (Gerardin et al, 2000). This suggests a link between the production of
Figure 3: A comparison of the macaque (A) and human (B) cerebral cortex. Yellow areas in both are the primary motor cortex, orange the premotor cortex. The red areas indicate the hypothesised homologue cortical motor areas that relate to communication and language, F5 in the monkey, and areas 44 in the
human, also known Broca’s area. Taken from Fogassi & Ferrari (2007:2)
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language and motor movements of the hands and limbs which is strengthened by the
finding that signed language also activates Broca’s area (Horwitz et al, 2003).
The human mirror system differs from the monkey mirror neuron system in
certain aspects: for example while monkey mirror neurons do not fire in the absence
of a goal-‐less grasp, these ‘intransitive meaningless movements’ do excite a response
in the human mirror system (Rizzolatti & Craighero, 2004:176). Corballis (2012b)
argues that in this case, an early language system incorporated symbolic actions and
representations and not simply objects in the here-‐and-‐now. He argues that this
system may therefore have been involved in the critical step in the development of
language from a capacity of simple communication to one in which our ancestors
were capable of ‘mental time travel’, the ability to express events in a separate time
and space from the present which Corballis & Suddendorf (2007:310) view as a
prerequisite for, and uniquely human aspect of, language.
Corballis (2012b:109) does not downplay the importance of mirror system in
humans: ‘in the course of evolution, the system initially specialised for grasping
provided the basis for the subsequent emergence of an intentional communication
system based on manual gestures’. This view appears to be the most likely based on
the evidence from mirror neurons in both monkeys and humans, where the system
that allowed imitation was developed to allow mimesis and a basic gestural
communicative system.
3.1.1 Reflections on Mirror Neurons and Theory of Mind Since the mirror system ‘gives the observer a first-‐person understanding of…the goals
and intentions of other individuals’ (Rizzolatti & Sinigaglia, 2010:264), mirror neurons
have also been cited as important in the development of ‘theory of mind’, a critical
prerequisite for co-‐operative behaviour and language (Gallese & Goldman, 1998).
Theory of mind is the ability to empathise with another individual and to
realise that they have knowledge and perspectives that are different to one’s own
(Premack & Woodruff, 1978). It has been cited as a uniquely human ability (Penn et
al, 2008), is inextricably linked to the language faculty (Malle, 2002), and has been
described as a precondition for the acquisition of language (Origgi & Sperber, 2000).
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Autistic children, whose social disability is characterised by a lack of empathy
and extreme difficulty in language learning (Carpenter & Tomasello, 2000), have been
suggested to lack full theory of mind (Baron-‐Cohen et al, 1985). Some suggest that a
dysfunction in the mirror system is responsible for this deficiency, and in turn this
affects the ability to acquire language (Williams et al, 2001). Further, those with
autism consistently produce fewer gestures, and these are developmentally less
advanced than those without autism (Buitelaar et al, 1991; Mundy et al, 1986). They
also show difficulty imitating the body movements of others (Williams et al, 2004) and
have a host of motor deficits (Ming et al, 2007). If we accept that the mirror system,
imitation, language and gesture are all interlinked, then the autistic child provides an
example of this connection by the absence of these features.
It is worth noting that theory of mind may well have been a later addition to
language, as it is not found in apes (controversially, Call & Tomasello, 2008). The
earliest language would not have necessarily involved taking into account another’s
mind; when simply referring in iconic expressions, this may simply have influenced
behaviour in another individual without the demonstration of joint attention (Malle,
2002) before developing into a more sophisticated form in which gestures were
mutually made and understood.
3.2 The Motor Theory of Speech Perception Corballis takes the motor theory of speech perception, first posited by Liberman et al
(1967) as evidence that language was originally based on a system of gestures. The
motor theory posits that humans comprehend speech based primarily on articulatory
gestures of the vocal apparatus rather than an acoustic signal. Corballis therefore
argues that ‘the shift (between speech and sign language) is not so much from vision
to audition as from one kind of gesture to another’ (2009:24). He links this to the
mirror system in humans, and asserts that articulations are simply vocal gestures. I
find this argument largely unconvincing however, and it seems more likely that
speech may have emerged as the result of the ‘expanding spiral’ that Arbib
(2005b:22) describes. He argues that H. Habilis through to H. sapiens communicated
via a gestural protolanguage, which provided the neurological scaffolding for the
emergence of a spoken protolanguage. These two systems then developed
19
simultaneously in the hominid line in an ‘expanding spiral’ that led to a relatively
complex gestural language before the emergence of proto-‐speech. This, along with
other possibilities, is discussed in greater detail later in section 5.
3.3 Bipedalism and Brain Growth
Many argue that bipedalism was a crucial factor in the emergence of human language
(Corballis, 2002; Gillespie-‐Lynch et al, 2014). Although it is difficult to date precisely
when our ancestors began to walk upright, fossil and genetic evidence place the date
at around 5-‐7 million years ago (Rosenberg & Trevathan, 2014). This had tremendous
implications for the evolution of our species: walking upright freed the hands for the
later emergence of tool use, as well as having implications for speech as the larynx
descended to a position where vocal control was possible, but perhaps only with the
emergence of Homo sapiens (Corballis, 2002). As the feet became less functional than
in our chimpanzee relatives, the neural space for control of the feet diminished in the
Homo line and allowed neural reorganisation for greater control of the hands.
Further, it has been shown that control of the hands is experience-‐led, so the more
the hands are used, the greater neural space is dedicated to them in comparison to
the feet (Richards, 1986; Corballis, 2002). Donald (1991:162) argues that later
obligate bipedalism in the Homo genus, with an arboreal lifestyle no longer necessary,
would have freed the hands and arms for a variety of uses including intentional
communication and ‘mimetic culture’. This is differentiated from the mimicry that
some animals possess (e.g. parrots) and imitation, somewhat limited to apes, in that it
is not literal, and involves ‘the invention of intentional representations’ (1991:169)
that are creative and novel. Corballis adds that a feature of gestural communication
allowed by bipedalism was the ability to ‘move in four dimensions’ (2009:32), allowing
mimetic displays of actual events using the hands which can incorporate a dimension
of time, a feature of mental time travel mentioned previously.
Bipedalism marks the split of the Homo line from the line of the nonhuman
primates, and was accompanied by a growth of the brain (Corbalils 2002). Although it
took roughly 4 million years from the earliest onset of bipedalism to a marked
increase in brain size in the hominid line (Nelson, 2009), it is possible that early
20
hominids such as Homo habilis had the capacity for a protolanguage based on manual
gestures in part due to a significantly larger brain size in all subsequent species of
Homo than in chimpanzees and other extant apes (Fig. 4). This is strengthened by the
discovery of enlarged Broca’s and Wernicke’s areas in endcocasts of Homo habilis
skulls (Tobias, 1998), which may indicate that this species had some semblance of
language, likely a system of gestures.
3.4 Adaptations for Speech – A Modern Phenomenon?
It has been inferred that articulate speech would not have been possible until
relatively late in the hominid lineage, due to the extensive changes to the vocal tract
and neurological control of vocalisation and breathing that may not have been
complete until the emergence of Homo sapiens ~170,000 years ago (Lieberman 1998;
Stokoe, 2001).
3.4.1 Changes to Anatomy – Speech Came Later The vocal tract of chimpanzees is incredibly limited in comparison to modern humans;
while humans can articulate a vast array of speech sounds, chimpanzees are limited
to a small repertoire of phonemes that is infinitely less flexible than in human speech
(Lieberman, 1975). This is due to the shape of the tongue and larynx (fig.5).
Figure 4: Comparison of brain size in extant primates and other species, taken from Corballis (2002:89).
21
The descent of the larynx depicted in fig.5 played a pivotal role in the
evolution of human speech; some suggest that this was kick-‐started by the advent of
bipedalism (DuBrul, 1976), but this remains controversial (Fitch, 2000). Nevertheless,
the new shape of the larynx made it possible to move the tongue both vertically and
horizontally inside the mouth, altering the shape of the vocal tract sufficiently to
produce a wide array of vowels and consonants pivotal to human speech that are
unavailable to chimpanzees. This descent is also found in the growth of infants to
children to adults; while still suckling the baby is capable of breathing and ingesting
liquid simultaneously, a capacity shared by apes (Fitch, 2000), before descending
when it reaches age 3 or 4 (Sasaki et al, 1977). This is a costly transformation as it
makes humans more susceptible to choking due to the convergence of respiratory
and digestive pathways, but some suggest that this was a worthwhile evolutionary
price to pay when the result is speech (Van Driem, 2005).
Fossil records have proven inconclusive in attempting to show that this
descent was also complete in Neanderthals (Fitch, 2000), but from the evidence
available it seems plausible that the position of the larynx and hyoid bone in
Neanderthals led to a basic phonetic ability, more complex than other primates but
less complex than in modern Homo sapiens (Crelin, 1987). Lieberman (1998) argues
that the adjustments necessary for vocal language were not complete in
Neanderthals, perhaps as recently as 30,000 years ago, due to the absence of a
Figure 5: Vocal tracts of chimpanzees (b) and humans (c). Red= Tongue body, Yellow= Larynx, Blue= Air sacs (distinct to apes). Taken from Fitch (2000:260).
22
flattened, human like-‐face to restrict the length of the vocal tract, which in humans
makes it possible to produce fluent speech. Since Neanderthal remains show signs of
tool making and cultural practices, it is safe to assume that they were neurologically
capable of a co-‐operative form of protolanguage, and because they were unable to
produce the fluent speech present in Homo sapiens, but retain the manual ability of
their and our ancestors, this was more likely to be a system reliant on gestures
(Nelson, 2009).
3.4.2 The Hypoglossal Canal, Articulation and Breathing Control
The nerves that allow articulations of the tongue pass through the hypoglossal canal,
located at the base of the skull. These allow the fine control necessary for human
speech (Kay et al, 1998). It has been found that the hypoglossal canals of
Australopithecus as well as Homo habilis are similar in size to extant Pan species, and
are significantly smaller than those present in modern and ancient Homo sapiens (Kay
et al, 1998). This suggests that the vocal abilities of ancient hominids were not as
developed as modern humans, or indeed of Neanderthals, who also had enlarged
canals, although this may have been the result of an overall larger stature in general.
Additionally, evidence from Maclarnon & Hewitt (1999) has shown that breathing
control, essential for the production of fluent speech, would not have been fully
evolved until around 1.6 million to 100,000 years ago. This was surmised from an
examination of the fossilised thoracic vertebral canal, which carries nerves that
innervate the muscles involved in and around the thorax, allowing for voluntary
breath control. A human-‐like appearance was not present in Australopithecines,
Homo ergaster, or early Homo erectus, whose thoracic canals were similar in size and
structure to extant ape species.
3.4.3 FOXP2 The FOXP2 gene has largely been referred to as ‘the language gene’ by the media
(BBC News, 2009), after it was discovered that a mutation of the gene in many
members of a family led to severe language impairments. This reductive labelling
reduces the complexity of the gene’s role in language: more specifically the disruption
of the gene causes non-‐activation in Broca’s area during verb generation and difficulty
23
in coordinating orofacial movements, leading to atypical speech delivery (Lai et al,
2001; Watkins et al, 2002; Liégois et al, 2003). The import of these finding is twofold;
FOXP2 is clearly involved in both the articulation of speech as well as the function of
Broca’s area, both critical for the delivery of speech. The FOXP2 gene has undergone
two mutations since the split between hominids and chimpanzees (Corballis, 2009),
and while the gene has supposedly been detected in a 45,000 year old Neanderthal
fossil, which in turn suggests it may date back 700,000 years (Krause et al. 2007; Noonan et al. 2006), this finding has been criticised by Coop et al. (2008) who claim
that this was more likely due to contaminated samples or the result of interbreeding
between Neanderthals and Homo sapiens. As previously discussed, Neanderthals are
unlikely to have possessed the ability to speak anyway. Nevertheless, if this particular
variant of gene has emerged relatively recently in the hominid line, most estimates
range between 38,000 to 200,000 years ago (Enard et al, 2002; Pinker, 2003), this
may have coincided with the emergence of Homo sapiens. Corballis (2004:96) argues
that ‘it is possible that mutation of FOXP2 was the most recent event in the
incorporation of vocalization into the mirror system, and thus the refinement of vocal
control to the point that it could carry the primary burden of language’. The
emergence of FOXP2 therefore may have been the crucial factor for linking gesture to
speech: Broca’s area, a crucial seat of the mirror system, may have been adapted by
the mutation of FOXP2 to allow articulatory control of vocalisations in Homo sapiens
after a gestural system had already been in place previously.
Therefore it seems likely that while hominids had developed the cognitive
capacity to use a form of protolanguage, to manipulate their limbs, to use symbols
and mimesis, their vocal and breathing apparatus were ill-‐equipped to serve an
articulate speech system until the emergence of Homo sapiens who possessed
greater control of their vocalisations and breathing, as well as a proclivity for speech
due to the emergence of the FOXP2 gene.
4. Sign Language So far I have focused on cognitive preadaptations for a gestural language, and now I
turn to evidence from the utility and naturalness of sign, as well as from the
24
formation of novel signed languages. This can shed light on how a gestural system
could have arisen in early humans, against the argument of a vocal language origin.
While it was previously thought that ‘the manual sign language must be viewed as
inferior to the verbal as a language’ (Myklebust 1957:242), it has since been proved
that sign languages are full languages, capable of all the syntactic and abstract
complexity present in speech (Stokoe, 1960). Modern day vestiges of an ancient
gestural system can still be observed: we gesticulate as we speak, all cultures use
gestures in their repertoire, children gesture before they can speak and even
congenitally blind children use both iconic and deictic gestures without ever seeing or
having the chance to copy them (Acredolo & Goodwyn, 1988). This led Iverson &
Goldin-‐Meadow (1997:466) to suggest that gesture plays ‘a role for the speaker that
is independent of its role for the listener’. In addition, spoken and signed languages,
despite the differences in input, i.e. the auditory versus the visual, are processed in
the same areas of the brain and the systems that support them are near identical
(MacSweeney et al, 2008). All this suggests that the capacity for signs and gestures to
communicate meaning is inbuilt, natural and integral to language function. Below I
examine the form, function and defining features of various types of languages
characterised by their use of gesture, from the pre-‐verbal stage in children to
spontaneous languages created by adults to show how these contribute to the
discussion of the gestural theory of language emergence.
4.1 Lateral isation of Language and Handedness Language in the brain is lateralised mainly in the left hemisphere, a finding initially
posited by Paul Broca when he observed that damage to the left hemisphere causes
aphasia but damage to the right does not (Broca, 1861). Recent studies have
confirmed this bias (Knecht et al, 2000), which in turn provides insight into the
development of early language. The population-‐level bias of right handedness and
left-‐hemisphere language dominance are intimately connected, and it has been
suggested that this is due to an original right-‐handed manual dominance which in
turn developed the left side of the brain in language evolution (Corballis, 2012b;
McManus, 2002).
25
Since language is lateralised in the left hemisphere of the brain in more than
90% of right-‐handers (Tzourio-‐Mazoyer & Courtin, 2013) and around 88-‐90% of the
population have this handedness preference (Corballis, 2012b:115), it is suggested
that the two are intricately correlated. This is an ancient characteristic, as right-‐
handed dominance has been observed in early hominids from at least 1.5-‐1.6 million
years ago based on skeletal fossil evidence and observation of crafted tools (Walker
and Leakey, 1993). The fact that this kind of lateralisation was present at this time
again suggests that brain specialisation for language was underway in early hominids
(Haviland et al, 2010). Similarly, in deaf sign language speakers, linguistic signs are
made with the dominant hand (normally the right) while the other plays a diminished
role in communication (Brentari, 1998). Interestingly, this left-‐handed role is often
paralinguistic and emotional, typically right-‐hemisphere controlled functions
(Lausberg et al, 2007). In addition, children show a significant bias for symbolic
gestures using their right hand compared to non-‐symbolic gestures for which they
tend to use the left (Bates et al, 1986). Children’s hand preference in signing precedes
their use of a dominant hand in object manipulation – the hand they use for signing is
significantly correlated with the hand that eventually becomes dominant for other
activities (Bonvillian & Richards 1993). This again demonstrates that handedness,
language-‐like gestures and lateralisation of language in the left hemisphere of the
brain are interconnected. This correlation between hand and language in both deaf
and hearing speakers, bolstered by the fact that symbolic gestures and speech are
processed in the same (left hemisphere) area of the brain (Xu et al, 2009) therefore
lends credence to the gesture-‐first argument.
4.2 Chi ld Language Another of Bickerton’s ‘living fossils’ (1990:105), child language, may represent what
a protolanguage may have been like in our forebears. Following Haeckel’s (1866)
‘ontogeny repeats phylogeny’ theory, in a more modern sense applied to language
evolution by Bickerton (1990:15) where ‘the ontogenetic development of language
partially replicates its phylogenetic development’, when applied to both gesture and
speech, an analysis of the capabilities of deaf and hearing children can elucidate what
part gesture played in language emergence.
26
4.2.1 Manual Babbling Laura Petitto (2000:4) describes that both deaf and hearing children begin to acquire
their respective signed and spoken languages at the same rate and at the same ages
of development, starting with babbling at around 7 months, right through until the 2-‐
word stage at around 16-‐22 months. Deaf children exposed to sign language alone by
their sign language-‐using parents typically exhibit a manual babbling stage involving
the performance of discrete elements of sign language in much the same way as
hearing children manipulate the spoken sound units of their language, e.g. ga-‐ga-‐ga
(Petitto, & Marentette, 1991). This implies that gesture is a modality in which
language is pre-‐programmed to thrive, and is just as natural and useful as a vocal
system. While babbling was previously understood to have been a precursor to
speech, it is now more accurate to describe it as a precursor to language, as it can be
achieved in either modality (Corballis, 2002).
4.2.2 Children’s Gestures Manual gestures are also observed in hearing children, and frequently occur before
they learn to speak: they point to objects to draw an adult’s attention before they
assign the object a word, and the earlier this happens the earlier the child will
produce a word for the object, suggesting an association between gestures and the
development of language (Özçaliskan & Dimitrova, 2013). These deictic gestures (i.e.
pointing) aid infants in understanding the association between symbols and referents,
as well as establishing the beginnings of joint attention at around one year of age-‐
children do not just point to objects for requests, they also point to objects already
within an adult’s gaze, indicating that attention to the object is shared (Tomasello,
2008). As mentioned previously, joint attention is pivotal for language development,
and the observation in children that joint attention is observed in manual gestures
before speech manifests itself strengthens the gestural argument.
Children also display the use of iconic gestures, which emerge slightly later
than deictic gestures, around 11-‐12 months (Özcaliskan & Goldin-‐Meadow, 2005).
Although less frequent than other gestures, these are far more language-‐like, assign
properties to referents and allow greater freedom than words in describing and
assigning properties to objects in the real world, much as our mute ancestors would
27
have had cause to do. Essentially, most argue that infants, provided with some kind of
input, use gestures more frequently to refer to objects and activities before they use
words for the same cause (Bates, 1976; Özcaliskan & Goldin-‐Meadow, 2005). Gesture
use also paves the way for children’s first nouns (Iverson & Goldin-‐Meadow, 2005)
and predicts the richness of their future language: those who use more iconic
gestures earlier in life develop larger vocabularies by 2 years of age, showing a strong
link between gesture use and overall language ability (Acredolo & Goodwyn, 1988;
Özçaliskan & Dimitrova, 2013).
Iverson et al (1994) observed hearing Italian children between 16 and 20
months of age to assess their gesture use; an interesting finding was that while the
children initially relied on agents to bolster their labelling, e.g. drinking from a toy cup
instead of copying the motion of drinking with the hand alone, this activity had
significantly diminished by 20 months. Instead, the children increasingly used
gestures dependent on movement without the use of an agent, e.g. flapping arms for
bird, and predicate gestures, e.g. holding the fingers close together to signify small.
They argue that this supports a theory in which gestures, over the course of cognitive
development become decreasingly context-‐bound, with the use of vehicles less
necessary as the child develops the ability to represent objects symbolically. This
supports Werner and Kaplan (1963) who argue that gestures help establish a
framework for a transition from object-‐bound communication to less object-‐related
gestures through to abstract symbolic representations that are then used in word-‐
referent relationships. This brings to mind the process of conventionalisation, ‘the
shift over tome from iconic gestures to arbitrary symbols’ (Gentilucci and Corballis,
2006:950) which is further explored in the following section in relation to novel sign
languages.
4.3 Novel Sign Languages
While dominant sign languages such as ASL and BSL have become ubiquitous,
established languages in modern culture, new sign languages, established over a
short period of time in differing contexts have been taken as support for a gesture-‐
first account (Fay et al, 2014, Sandler et al, 2005). The emergence of pidgin and creole
sign languages, such as Nicaraguan Sign Language (LSN) and Al-‐Sayyid Bedouin Sign
28
Language (ABSL), as well as the well-‐documented, widespread phenomenon of
‘homesign’ (Goldin-‐Meadow, 2003) has shed light on the properties and evolution of
an embryonic language. Greenfield et al (2008:36) describe these ‘languages’ as ‘the
linguistic limit of what can be developed without a cultural environment provided by
language-‐using humans.’ In this sense, they are the nearest equivalent to a system
that may have been utilised by pre-‐linguistic hominids; a protolanguage produced in
the absence of an established language-‐enriched environment.
4.3.1 Homesign in Deaf Children
Deaf children who grow up in homes with hearing parents who do not use sign
language to communicate have demonstrated their own communicative system that
has been coined ‘homesign’ (Goldin-‐Meadow & Mylander, 1984). Children develop
these systems spontaneously in an environment devoid of an appropriate language
community; in this sense they have no usable linguistic input, and are ‘truly creating
language from scratch’ (Fay et al, 2014:9). Goldin-‐Meadow argues that ‘[t]he
children…lack access to a useable model of language…the gestures that the deaf
children use to communicate are structured in language like-‐ways. The children are
inventing their own, simple language’ (2003:xvii). The claim that homesign constitutes
a language per se is controversial (Morgan, 2005), but it does seem likely that this
idiosyncratic, simple, proto-‐grammatical system may recapitulate the features of a
gestural protolanguage that may have been present in our ancestors. Goldin-‐Meadow
(2002:369) herself acknowledges this potential ‘these are forces that are likely to play
a role in language creation every time it takes place, perhaps even the first time’.
Below is an example of the typical structure of homesign, taken from Slobin
(2004:13):
Patient + act (e.g., CHEESE EAT) Actor + act (e.g., YOU MOVE) Patient + act + agent (e.g., SNACK EAT YOU)
This displays a two or three-‐word ordering of signs, and a kind of proto-‐grammar of
the type that has previously been discussed in language-‐trained apes, as well as the
early language of hearing children. In addition, homesign displays noun-‐verb
distinction, considered a language universal (Smith, 1999). For example, one of the
29
participants observed by Goldin-‐Meadow et al (1994) differentiated between nouns
and verbs in different contexts. When using the sign for ‘twist’ in the verb sense, e.g.
‘twist the jar open’, he was more likely to produce the sign with (i) without
abbreviation, i.e. performing the twisting gesture multiple times, (ii) with inflection, in
this case gesturing towards an object to be twisted, and (iii), the gesture is performed
after indicating the object to be twisted. In contrast the gestural noun version of this,
e.g. ‘a twistable object’ is produced only once, in a neutral position, normally near to
the body, and before indicating the object (Goldin-‐Meadow, 2006).
Goldin-‐Meadow (2003) suggests that although homesign does exhibit some
morphological, lexical and syntactic complexity, the signs tended to be mainly
referential when the signer is limited to a group, essentially, of one (themselves).
However, she also maintains that the most robust, essential features of language
remain, those that are necessary for a communicative system to work. Homesign, left
to this group of one, stagnates and does not progress to full language (Slobin, 2005).
However, when this group of homesigners is expanded away from parents
who do not enrich the child’s experience and are put in contact with like-‐minded
interlocutors, the possibility of novel sign languages to become fully-‐fledged is
exponentially increased. The crucial factor is an interacting community, providing an
‘alignment between speakers [which] is essential for a lexicon to stabilize’ (Fay et al,
2014:10). This is the focus of the following section.
4.3.2 Nicaraguan Sign Language, (LSN) and Idioma de Signos Nicaragünese (ISN)
The activity of homesign takes on an increased significance when those who use it are
suddenly removed from a speech-‐dominated sphere and subsequently immersed in a
deaf, sign-‐dominant culture. This is precisely what happened when Nicaragua opened
its first school for the deaf in 1978; the children, who previously had no interaction
with other deaf people or sign language, had each already devised their own system
of homesign (Senghas, 1995). When they came together at the new school they were
taught lip reading and Spanish but with limited success. However, when they were
allowed to interact with each other using their various homesign systems, which were
essentially pidgins, they began to converge on a simple sign language, LSN (Senghas &
Coppola, 2001). This was also essentially a pidgin, with a simple structure and little to
30
no grammar, and was used by the first entrants to the school in 1978. Since then, the
younger children who enter the school have been exposed to LSN by the older
children, and have consequently produced a more complex, compact, primary sign
language with grammar, ISN. Greenfield, Lyn and Savage-‐Rumbaugh assert that ‘the
sign language codified and became more complex with each succeeding generation’
(2010:36) in this sense the pidgin become a creole over time. The system, created
through ‘abrupt creolization’ (Senghas, 1995:1) contains inflectional verb
morphology, noun classifiers and other features unique to fully-‐fledged languages.
Senghas & Coppola (2001:328) argue that ‘[t]he emergence of Nicaraguan Sign
Language offers an opportunity to examine the processes common to language
learning, language change, and language genesis’. The ability of these children to
essentially create a language where none existed before, especially the evolution
from creating a homesign system in the absence of linguistic input to the creolization
of a new, fully fledged language, demonstrates the capacity of language to develop
from basic, iconic gestures to a fully grammatical system in the manual mode. This
window into early language emergence is viable not only in Nicaraguan sign language
and homesign, but also for a more recently studied novel sign language, Al-‐Sayyid
Bedouin Sign Language.
4.3.3 Al-‐Sayyid Bedouin Sign Language (ABSL) This is another sign language that has appeared de novo, in a smaller population than
LSN, in a Bedouin community in the Negev desert in Israel. The inhabitants have an
unusual tendency for deafness, with around 150 out of 3,500 members having
inherited a condition leaving them profoundly deaf. The sign language that has been
created is now in its third generation, having been developed over approximately the
last 70 years (Senghas, 2005).
In this time researchers have found that the language is completely distinct
from both spoken and other sign languages found nearby such as Israeli Sign
Language, which has both a different word order and is acknowledged as different by
signers of both languages (Sandler et al, 2005). ABSL is now recognised as a fully-‐
fledged sign language, able to express a variety of abstract ideas and events displaced
from the present (Fox, 2008). In addition, (Sandler et al, 2005:2661) note that ‘In the
31
space of one generation from its inception, systematic grammatical structure has
emerged in the language’. This grammar emerged in the absence of outside influence
from other languages, and was formed after a conventionalised set of lexical items
had already been established, showing a gradual increase in linguistic complexity akin
to the way language might have originally emerged.
Sandler et al (2005) also found that the word order employed in ABSL was
overwhelmingly SOV. This is interesting when paired with research from Goldin-‐
Meadow et al (2008), which found that hearing speakers of various languages all
abandon their language’s own word order when asked to describe events using
gesture without speech in favour of the same SOV word order in different non-‐verbal
tasks. This suggests that there may be an innate, natural human tendency for this
particular word order used in gestural communication, and it ‘may reflect a natural
disposition that humans exploit not only when asked to represent events nonverbally,
but also when creating language anew’ (2008:9167). This concurs with Newmeyer’s
(2000) postulation that early protolanguage is likely to have had an SOV word order.
Sandler et al (2005:2665) add: ‘The appearance of this conventionalization at such an
early stage in the emergence of a language is rare empirical verification of the unique
proclivity of the human mind for structuring a communication system along
grammatical lines.’
4.3.4 Creating a New Communication System from Scratch Natural languages created from scratch have been discussed in 4.3.2 and 4.3.3. and
the below describes how a new language was created and developed in a simulated
community over a short period of time.
An additional finding of Pollick and de Waal’s ape gesture study (2007),
discussed in 2.2, was that bonobos used gestures more frequently than chimpanzees
to initiate a social interaction, 78% of the time, and that both species used gestures
alone more frequently than vocalisations or a combination of the two (Fig. 6).
32
The success of gesture to both initiate interactions as well as to solicit
responses in the two groups echoes Fay et al’s (2014) study in which a group of
people were tasked with creating a communication system from scratch. They found
that gestures were the most effective means of conveying meaning from one person
to another where no shared language was available to them (Fig. 7). Even when
gesture was combined with speech, this was found to be distracting and was less
effective than the use of gesture alone.
The study reveals a crucial point that I believe may have been pivotal in the
evolution of our own language: ‘participants initially use iconic signs to ground shared
0
20
40
60
80
100
Gestures Facial/ Vocal Combination Percentage of the time
(%)
Initiation of Social Interaction
Chimpanzees
Bonobos
Figure 6. Frequency of interaction type. Data from Pollick & de Waal (2007)
Figure 6: Success of each type of signal, judged by accuracy of identification. Taken from Fay et al (2014:5).
33
meanings, and over subsequent interactions these signs become increasingly aligned,
symbolic and language like’ (Fay et al, 2014:3). This echoes the findings of Iverson et
al (1994) about conventionalisation from the previous section, as well as with
Corballis’ theory that gestural signals could have ‘eventually conventionalized so that
other forms of representation, including spoken and written words, as well as more
abstract manual gestures, could suffice to carry the message’. (Corballis 2009:109).
Conventionalisation may have been a pivotal process in the emergence of
human language: manual gestures are the most likely candidate to have been the
original form of communication between cognitively evolved proto-‐hominids, as they
have ‘at least the potential to represent concepts iconically rather than in abstract
form. Once a set of iconic representations is established, increasing usage can then
lead to more stylized and ultimately abstract representation’ (Corballis, 2000). This
process is not a recent development among the deaf, and has been observed
naturally for at least hundreds of years. Darwin (1965/1872:64) quotes W.R. Scott’s
The Deaf and the Dumb (1870:12):
This contracting of natural gestures into much shorter gestures than the natural expression requires is very common amongst the deaf and dumb. This contracted gesture is frequently so shortened as nearly to lose all semblance of the natural one, but to the deaf and dumb who use it, it still has the force of the original expression.
De Waal (1982) has previously noted that primate gestures also become
conventionalised over time, from actions centred around objects to symbolic gestures
on their own, much like the process that is observed in homesigning children and
novel sign languages.
The importance placed by Saussure on the ‘arbitrariness of the sign’ (1916) as
a prerequisite for language has been a stumbling block in the attempt to classify sign
languages as full languages, since a large amount of signs are iconic in nature
(Corballis, 2012b). However, the examination of these novel sign languages and the
process of conventionalisation show that iconicity is not a necessity for signed
languages: original signs may be iconic, but over time these acquire aspects of
arbitrariness such as in the creolization from the more iconic LSN to the more
symbolic and language-‐like ISN. Furthermore, arbitrariness is often achieved as the
34
result of a need for expedience and convenience: Corballis (2009:32) quotes Charles
Hockett (1978:274-‐275):
When a representation of some four-‐dimensional hunk of life has to be compressed into the single dimension of speech, most iconicity is necessarily squeezed out. In one-‐dimensional projections, an elephant is indistinguishable from a woodshed. Speech perforce is largely arbitrary…we have learned to make a virtue of necessity.
The need for concision, speed and efficiency may well have been a driving force in the
transition from a primarily gestural to a primarily vocal mode in Homo sapiens, to
coincide with the increase in complexity of human culture through time (Corballis,
2009).
5. But why the switch to speech? Michael Corballis (2009:24) acknowledges the difficulty in explaining how if an original
system of gestures existed, then why is language today primarily spoken. He quotes
Robbins Burling (2005:123):
[T]he gestural theory has one nearly fatal flaw. Its sticking point has always been the switch that would have been needed to move from a visual language to an audible one.
Corballis then argues that the shift was a gradual process, and that the motor theory
of speech perception and the concept of ‘speech as gesture’ can go some way to
explaining the shift from a gestural modality to a spoken one. He cites evidence from
articulatory phonology, which posits that speech is itself a system of gestures of the
mouth, lips and so on, which is bolstered by the discovery of the McGurk effect
(McGurk & MacDonald, 1976). This is the phenomenon that when a sound is played
over the top of a video of a person producing a different speech sound, the viewer
reports hearing a different sound entirely to the one being spoken. However for me
this particular aspect of his argument is unsatisfactory, as the evidence against this
theory is somewhat insurmountable: the McGurk effect has been found to occur in
35
non-‐linguistic circumstances (Massaro 1998), and the theory is now generally seen as
false by the majority of linguists (Galantucci et al, 2006).
Nevertheless, others have attempted to explain how the transition may have
taken place with greater success: Arbib’s notion of an ‘expanding spiral’ (2005b:22) is
somewhat convincing:
Homo habilis through to early Homo sapiens had a protolanguage based extensively on manual gestures (‘protosign’) which … provided essential scaffolding for the emergence of a protolanguage based primarily on vocal gestures (‘protospeech’)
While this is in line with my own argument, Stokoe (2002) elaborates upon this idea
to form a picture of language emergence: gestures were the original signs, iconically
representing animals, objects, and things in the real world. Arbitrary vocalisations at
this point in history would have been useless. Movements of the body may have
represented the actions of these referents, creating a rudimentary syntax of the type
seen in homesign. This is referred to as ‘semantic phonology’ (Stokoe, 2002:82), and
describes hand shapes being parsed into a primitive noun and verb phrase, i.e. the
hand and its movement. In this model, over time the basic structure for language
ability was therefore present in hominids, having built upon the abilities of the LCA,
and bolstered by the advent of bipedalism. From this base of knowledge, the mirror
system propagated interaction between conspecifics, until eventually vocal signs
were incorporated into the repertoire, firstly scaffolding and then replacing manual
gestures as the anatomy of the vocal tract and brain became more suited to volitional
speech, at around the emergence of Homo sapiens.
Some also argue that natural selection has its place in a switch from the
manual to vocal mode (Pinker & Bloom, 1990): speech is less energy consuming than
manual gesturing, provides a method of communicating in the dark, and frees the
hands for manufacturing and pedagogy (Corballis, 2002). The switch to speech,
therefore, may have been advantageous in our ancestors, leading to the demise of
the Neanderthals as their language abilities languished, and the ‘human revolution’ of
Homo sapiens that began their domination of the planet. Kim Sterelny (2012:2143)
36
sums up a model in which natural selection, gesture and speech are interlinked, in
agreement with mine and Stokoe’s assessment and the importance of adaptation:
Speech has the marks of an incrementally constructed complex adaptation, and it evolved despite the costs of this re-‐organization. For that to be possible, selection for enhanced communication must have preceded the capacity to speak. We evolved speech as a result of living in a world in which communication was already important.
In any case, the change from a dominant manual mode to a primarily spoken one was
probably a gradual change, but perhaps was bolstered by the mutation of the FOXP2
gene that could have linked gesture to speech in Broca’s area. Whatever the case may
have been, it stands to reason that gesture was the original method of a type of
communication: the iconic nature of early signs for everyday occurrences in proto-‐
hominid lifestyles, and the cognitive, manual, anatomical and linguistic abilities that
they likely possessed all point towards gesture being the most natural and probable
mode of early linguistic interaction.
6. Conclusion While the task of tracing language’s emergence is speculative, empirically challenging
and necessarily multi-‐disciplined, I believe from the evidence that I have presented, a
system rooted in gesture is the most likely to have been the original form of
‘language’, albeit potentially in a proto-‐form. Early vocalisations would not have been
under the control necessary to construct complex phrases or even particularly diverse
phonemes, whereas at least the potential for some kind of meaningful gestural
communication has been present since at least the LCA some 6 million years ago.
Bickerton’s living fossils of an earlier protolanguage provided the original basis
for this discussion: the first of which was the language of trained apes. These
experiments showed the linguistic and cognitive capabilities of nonhuman primates,
as the closest extant link to the LCA and our forefathers of the hominid line. While
these animals show little to no cortical control of their vocalisations, which are
primarily emotional and reflex-‐based, control of their limbs is highly developed. They
showed aptitude in various types of signed language, and linguistic ability of the
37
extent of a potential protolanguage, or language-‐like cognitive abilities that may have
been present in our forebears. Homo erectus almost certainly had a gestural
protolanguage, as they possessed both the cognitive complexity and control of the
limbs present in ape species, but with a much larger brain.
Bickerton’s second fossil was child language: in this dissertation I have
discussed how hearing children routinely gesture before they speak, while deaf
children create their own systems of homesigns which for them function as a simple
language, with the type of complexity that we would expect to find in early hominids.
In addition, the naturalness of manual babbling and deictic gesturing in the
acquisition of language in an ontogenic and phylogenetic sense was elaborated,
coupled with the importance of theory of mind in language acquisition both today
and in prehistory.
Thirdly, in Bickerton’s model I have adapted, pidgin communication was also
seen as a critically important living fossil. Consequently an examination of the novel
sign languages, such as the homesign systems of the deaf, Nicaraguan Sign Language,
Al-‐Sayyid Bedouin Sign Language and a synthetically created language were explored
in an attempt to highlight the naturalness of sign language, its ability to be conceived
in an environment essentially devoid of linguistic input, and how it can be
conventionalised to become more symbolic and language-‐like over time.
When taken together, all these threads of evidence lead to the conclusion
that language originated from a system of manual gestures in our ancestors. With
further study of the brain’s role in language, as well as more complete fossil evidence
of the vocal tract and anatomy of early hominids, science may shed still more light on
how language originally emerged. Until then, how language came to be will still be the
question on everybody’s lips… or hands.
38
7. References Acredolo, L. E, & Goodwyn, S. W. (1988). Symbolic gesturing in normal infants. Child
Development, 59, 450-‐466. Aiello, L. C., Dunbar, R. (1993). Neocortex size, group size and the evolution of
language. Curr Anthropol. 34:184–193. Arbib, M. A. (2005a). From monkey-‐like action recognition to human language: An
evolutionary framework for neurolinguistics. Behavioural and Brain Sciences, 28, 105-‐167.
Arbib, M. A. (2005b). The Mirror System Hypothesis: How did protolanguage evolve?
In Language Origins, ed. Maggie Tallerman, 21-‐47. Oxford: Oxford University Press. Armstrong, D. F., Stokoe, W. C., & Wilcox, S. E. (1995). Gesture and the Nature of
Language. Cambridge: Cambridge University Press. Armstrong, D. F., & Wilcox, S. E. (2007). The Gestural Origin of Language. Oxford:
Oxford University Press. Arnold, K. and Zuberbuhler, K. (2006). Semantic combinations in primate calls.
Nature 441: 303–303. Bates, E. (1976). Language and context. New York: Academic Press. Bates, E., O'Connell, B., Vaid, J., Sledge, P. & Oakes, L. (1986). Language and hand
preference in early development. Developmental Neuropsychology, 2(1), 1-‐15. Baron-‐Cohen, S., Leslie, A. M., & Frith, U. (1985). Does the autistic child have a 'theory
of mind'? Cognition, 21, 37-‐46. BBC News. (2009). 'Language gene' effects explored. BBC News. Available from:
http://news.bbc.co.uk/1/hi/sci/tech/8355541.stm. [Accessed 17th April 2015]. Bickerton, D. (1990). Language and Species. University of Chicago Press. Bickerton, D. (1995). Language and Human Behavior. University of Washington Press,
Seattle, WA. Bonvillian, J. D. & Richards, H. C. (1993). The development of hand preference in
children’s early signing. Sign Language Studies 78:1–14. Bowie, J. (2010). Protodiscourse and the emergence of compositionality. In: Arbib, M.
A. and Bickerton, D. (eds.) The Emergence of Protolanguage: Holophrasis vs compositionality. Amsterdam: John Benjamins.
39
Brentari, D. (1998). A prosodic model of sign language phonology. MIT Press. Broca, P. (1861). Remarques sur la siège de la faculté du langage articulé, suivies
d’une observation d’aphémie. Bulletin de la Société Anatomique de Paris, 2, 330–357.
Buitelaar, J. K., Van Engeland, H., de Kogel, K. H., De Vries, H., Van Hooff, J. (1991).
Differences in the structure of social behaviour of autistic children and non-‐autistic retarded controls. J.Child Psychol. Psychiat. 32:995-‐1015.
Bulwer, J. (1644). Chirologia: or the naturall language of the hand. Composed of the
speaking motions, and discoursing gestures thereof. Whereunto is added Chironomia: or, the art of manuall rhetoricke. Consisting of the naturall expressions, digested by art in the hand, as the chiefest instrument of eloquence. London: Thomas Harper.
Burling, R. (2005). The Talking Ape. New York: Oxford University Press. Call, J. and Tomasello, M. (2008). Does the chimpanzee have a theory of mind? 30
years later. Trends in Cognitive Science. 12, 187–192. Carpenter, M., & Tomasello, M. (2000). Joint attention, cultural learning, and
language acquisition: Implications for children with autism. In A. M. Wetherby & B. M. Prizant (Eds.) Autism spectrum disorders: A transactional developmental perspective, pp. 31–54. Baltimore, MD: Paul H. Brookes Publishing.
Cheney, D. L., & Seyfarth, R. M. (2005). Constraints and preadaptations in the earliest
stages of language evolution. Ling. Rev. 22, 135–159. DOI: 10.1515/tlir.2005.22.2-‐4.135.
Chomsky, N. (1996). Powers and Prospects. Reflections on human nature and the
social order. London: Pluto Press. Chomsky, N. (2004). Language and Mind: Current thoughts on ancient problems. Part
I & Part II. In Lyle Jenkins (ed.) Variation and Universals in Biolinguistics. Amsterdam: Elsevier, pp. 379-‐405.
Coop, G., Bullaughev, K., Luca, F., & Przeworski, M. (2008). The timing of selection of
the human FOXP2 gene. Mol. Biol. Evol., 25, 1257–1259. Corballis, M. C. (2000). Did language Evolve from Manual Gestures? 3rd Conference
of The Evolution of Language ’00, France. Corballis, M. C. (2002). From Hand to Mouth: The Origins of Language. Princeton, NJ:
Princeton University Press.
40
Corballis, M. C. (2003). From mouth to hand: Gesture, speech, and the evolution of right-‐ handedness. Behavioral & Brain Sciences, 26, 199–260.
Corballis, M. C. (2004). FOXP2 and the mirror system. Trends in Cognitive Sciences
8:95–96. Corballis, M. C. (2007). The evolution of foresight: What is mental time travel, and is it
unique to humans? Behavioral and Brain Sciences 30, 299 –351. Corballis, M. C. (2009). The Evolution of Language. Year in Cognitive Neuroscience:
Blackwell Publishing, Oxford, pp. 19–43. Corballis, M. C. (2010). Mirror neurons and the evolution of language. Brain &
Language 112, 25–35. Corballis, M. C. (2012a). How language evolved from manual gestures. Gesture 12(2):
200–206. DOI: 10.1016/B978-‐0-‐444-‐53860-‐4.00006-‐4. Corballis, M. C. (2012b). Lateralization of the human brain. Progress in Brain Research,
195. 103-‐121. Corballis, M. C. & Suddendorf, T. (2007) Memory, time, and language. In: What makes
us human, ed. C. Pasternak. Oneworld Publications. Crelin, E. (1987). The Human Vocal Tract, Vantage Press. Darwin, C. R. (1872). The expression of the emotions in man and animals. London:
John Murray. Darwin, C. R. (1896). The Descent of Man and Selection in Relation to Sex. London:
William Clowes. (Work originally published 1871). de Condillac, E. B. (1746/1947). Essai sur l’origine des con-‐ naissances humaines,
ouvrage ou l’on réduit a un seul principe tout ce concerne l’entendement. Oeuvres philosophiques de Condillac. Paris: Georges LeRoy.
de Cordemoy, G.. (1972). Discours physique de la parole [A philosophical discourse
concerning speech, con-‐ formable to the Cartesian principles]. Delmar, NY: Scholars’ Facsimiles & Reprints, Inc (Work originally published 1688).
de Waal, F. (1982). Chimpanzee politics. Johns Hopkins University Press/Harper and
Row. de Waal, F. and Pollick, A. S. (2012). Gesture as the most flexible modality of primate
communication. In M. Tallerman and K. R. Gibson (eds.) The Oxford handbook of language evolution. Oxford: Oxford University Press, 82-‐9.
41
Deacon, T. (1997). The Symbolic Species: The Co-‐evolution of Language and the Human Brain. London: Penguin Books.
Donald, M. (1991). Origins of the Modern Mind. Cambridge, MA: Harvard University
Press. DuBrul, E.L. (1976). Biomechanics of speech sounds. Ann. New York Acad. Sci. 280,
631–642. Dunbar, R. (1996). Grooming, Gossip and the Evolution of Language. London: Farber
and Farber. Enard, W., Przeworski, M., Fisher, S.E., Lai, C.S.L., Wiebe, V., Kitano, T. (2002).
Molecular evolution of FOXP2, a gene involved in speech and language. Nature, 418, 869–871.
Fay, N., Lister, C.J., Ellison, T.M. & Golden-‐Meadow, S. (2014). Creating a
communication system from scratch: gesture beats vocalization hands down. Frontiers in Psychology. 5, 354-‐392.
Fitch, W.T. (2010). The evolution of speech: A comparative review. Trends in
Cognitive Sciences, 4, 258–267. Fogassi, L., & Ferrari, P. F. (2007). Mirror neurons and the evolution of embodied
language. Current Directions in Psychological Science, 16, 136–141. Fouts, R. S. (1975). Communication with chimpanzees. In G. Kurth & I. EiblEibesfeldt
(Eds.), Humanization und Verhalten, pp. 137-‐158. Stuttgart: Gustav Fischer Verlag. Fouts, R. S., Fouts D. H., & Van Cantfort, T. E. (1989). The Infant Loulis Learns Signs
from Cross-‐Fostered Chimpanzees. In. R. A. Gardner, B. T. Gardner, & T. E. Van Cantfort (Eds.) Teaching sign language to chimpanzees. Albany: State University of New York Press.
Fouts, R. S., & Rigby, R. (1977). Man-‐chimpanzee communication. In T. Sebeok (Ed.),
How animals communicate, pp. 1034-‐1054. Bloomington: Indiana University Press. Fox, M. (2008). Talking Hands: What Sign Language Reveals About the Mind. United
States: Simon & Schuster Adult Publishing Group. Galantucci, B., Fowler, C. A., and Turvey, M. T. (2006). ‘The motor theory of speech
perception reviewed’ Psychonomic Bulletin & Review, 13 (3): 361–377. Gallese, V. & Goldman A. (1998). ‘Mirror neurons and the simulation theory of
mindreading’. Trends in Cognitive Sciences 2 (12): 493–501. doi:10.1016/S1364-‐6613(98)01262-‐5.
42
Gardner, R. A., & Gardner, B. T. (1969). Teaching sign language to a chimpanzee. Science, 165, 664–672.
Gentilucci, M., & Corballis, M. C. (2006). From manual gesture to speech: A gradual
transition. Neuroscience and Biobehavioral Reviews, 30, 949–960. Gerardin, E., Sirigu, A., Lehericy, S., Poline, J. B., Gaymard, B., Marsault, C. (2000).
Partially overlapping neural networks for real and imagined hand movements. Cerebral Cortex, 10, 1093–1104.
Gillespie-‐Lynch K., Greenfield P. M., Lyn H. and Savage-‐Rumbaugh S. (2014). Gestural
and symbolic development among apes and humans: support for a multimodal theory of language evolution. Front. Psychol. 5:1228. doi: 10.3389/fpsyg.2014.01228.
Goldin-‐Meadow, S. (2002). Getting a handle on language creation. In T. Givón, B.F.
Malle (Eds.), The Evolution of Language out of Pre-‐language, John Benjamins Publishing Company: Amsterdam, pp. 343–355.
Goldin-‐Meadow, S. (2003). The Resilience of Language: What Gesture Creation in
Deaf Children Can Tell Us About How All Children Learn Language. Psychology Press.
Goldin-‐Meadow, S. (2006). Nonverbal communication: The hand’s role in talking and
thinking. In D. Kuhn & R. Siegler (Eds), The handbook of child psychology: Cognition, perception, and language, 6th ed., pp. 336–372. Hoboken, NJ: Wiley.
Goldin-‐Meadow, S. & Mylander, C. (1984). Gestural communication in deaf children:
The effects and non-‐effects of parental input on early language development. Monographs of the Society for Research in Child Development 49, 3-‐4, Serial No. 207.
Goldin-‐Meadow, S., Mylander, C., Butcher, C., & Dodge, M. (1994). Nouns and verbs
in a self-‐styled gesture system: What’s in a name? Cognitive Psychology, 27, 259-‐319.
Goldin-‐Meadow, S., So, W-‐C., Özyürek, A., Mylander, C. (2008). The natural order of
events: how speakers of different languages represent events nonverbally. Proceedings of the National Academy of Sciences USA 105:9163–68.
Goodall, Jane (1986). The chimpanzees of Gombe: Patterns of behavior. Cambridge,
MA: Harvard University Press. Greenfield, P. M., Lyn, H. & Savage-‐Rumbaugh, E. S. (2008). Protolanguage in
ontogeny and phylogeny: Combining deixis and representation. Interaction Studies 9:34–50.
43
Greenfield, P. M. and Savage-‐Rumbaugh, S. (1990). Grammatical combination in Pan paniscus. In Parker, S. T. and Gibson, K. M. Language and Intelligence in Monkeys and Apes: Comparative Developmental Perspectives. Cambridge: Cambridge University Press, pp. 540-‐579.
Haeckel, Ernst. (1866). Generelle morphologie der organismen [General Morphology
of the Organisms]. Berlin: G. Reimer. http://www.biodiversitylibrary.org/item/22319#page/11/mode/1up [Accessed April 9th, 2015].
Hauser, M.D., Fitch, W.T., Chomsky, N. (2002). The faculty of language: what is it, who
has it, and how did it evolve? Science 298, 1569–1579. Haviland, W., Prins, H., Walrath, D. and McBride, B. (2010). Anthropology: The Human
Challenge. Cengage Learning. Hewes, G.W. (1973). Primate communication and the gestural origin of language.
Current Anthropology, 14 (1-‐2): 5-‐24. Hobaiter, C., Leavens, D. A., and Byrne, R. W. (2014). Deictic gesturing in wild
chimpanzees (Pan troglodytes)? Some possible cases. J. Comp. Psychol. 128, 82–87. doi: 10.1037/a0033757.
Hockett, C. (1978). In search of love’s brow. American Speech, 53, 243–315. Horwitz, B., Amunts, K., Bhattacharyya, R., Patkin, D., Jeffries, K., Zilles, K., et al.
(2003). Activation of Broca’s area during the production of spoken and signed language: A combined cytoarchitectonic mapping and PET analysis. Neuropsychologia, 41, 1868–1876.
Hurford, J. R. (2003). The Language Mosaic and its Evolution. In Language Evolution,
edited by Christiansen, M. and Kirby, S. Oxford: Oxford University Press, pp.38-‐57. Iverson, J. M., & Goldin-‐Meadows, S. (1997). What’s communication got to do with it?
Gesture in children blind from birth. Developmental Psychology, 33, 453–467. Iverson, J. M., & Goldin-‐Meadow, S. (2005) Gesture paves the way for language
development. Research Report: Psychological Science, 16(5), 367 – 371. Iverson, J.M., Capirci, O. and Caselli, M.S. (1994). From communication to language in
two modalities. Cognitive Development 9, 23–43. Kay, R. F., Cartmill, M., & Barlow, M. (1998). The hypoglossal canal and the origin of
human vocal behavior. Proc. Nat. Acad. Sci. USA, 95, 5417–5419. Kendon, A. (1995). Gestures as illocutionary and discourse structure markers in
southern Italian conversation. Journal of Pragmatics 23: 247-‐279.
44
Kendon, A. (2004). Gesture: Visible Action as Utterance. Cambridge: Cambridge
University Press. Kirby, S. (2007). The evolution of language. In Dunbar, R. and Barrett, L. (eds.) Oxford
Handbook of Evolutionary Psychology. Oxford: Oxford University Press. Knecht, S., Dräger, B., Deppe, M., Bobe, L., Lohmann, H., Flöel, A., Ringelstein, E.-‐B. &
Henningsen, H. (2000). Handedness and hemispheric language dominance in healthy humans. Brain, 123:2512–18.
Knight, C. (2008). Honest fakes and language origins, Journal of Consciousness
Studies, 15(10-‐11): 236-‐48. Krause, J., Lalueza-‐Fox, C., Orlando, L., et al. (13 co-‐authors). (2007). The derived
FOXP2 variant of modern humans was shared with Neandertals. Curr Biol, 17:1908–1912.
Kumar, S., Filipski, A., Swarna, V., Walker A., and Hedges, B.S. (2005). Placing
confidence limits on the molecular age of the human–chimpanzee divergence. Proceedings of the National Academy of Sciences, U.S.A. 102, 18842–18847.
Lai, C. S., Fisher, S. E., Hurst, J. A., Vargha-‐Khadem, F., & Monaco, A. P. (2001). ‘A
forkhead-‐domain gene is mutated in a severe speech and language disorder’. Nature, 413 (6855): 519–23.
Lausberg H., Zaidel, E., Cruz, R. F., and Ptito, A. (2007). Speech-‐independent
production of communicative gestures: Evidence from patients with complete callosal disconnection. Neuropsychologia, 45: 3092-‐3104.
Liégeois, F., Baldeweg, T., Connelly, A. Gadian, D. G, Mishkin, M., & Vargha-‐Khadem,
F. (2003). Language fMRI abnormalities associated with FOXP2 gene mutation. Nat. Neurosci., 6, 1230– 1237.
Lenneberg, E.H. (1967). Biological Foundations of Language. New York: John Wiley
and Sons. Liberman, A. M., Cooper, F. S., Shankweiler, D. P., & M. Studdert-‐Kennedy. (1967).
Perception of the speech code. Psychological Review, 74, 431-‐461. Lieberman, P. (1998). Eve Spoke: Human Language and Human Evolution. New York:
Norton. Lieberman, P. (1975). On the Origins of Language: An Introduction to the Evolution of
Human Speech. New York: Macmillan.
45
MacLarnon, A. & Hewitt, G. (1999). The evolution of human speech: The role of enhanced breathing control. American Journal of Physical Anthropology, 109:341–63. MacNeilage, P. (2011). The Evolution of Phonology, In Tallerman, M. and Gibson, K.
(eds.) The Oxford Handbook of Language Evolution. Oxford: Oxford University Press.
MacSweeney, M., Capek, C. M., Campbell, R., Woll, B. (2008). The signing brain: The
neurobiology of sign language. Trends in Cognitive Sciences 12, 432-‐440. Maestripieri, D. (2005). Gestural communication in three species of macaques
(Macaca mulatta, M. nemestrina, M. arctoides): use of signals in relation to dominance and social context. Gesture, 5, 55-‐71.
Malle, B. F. (2002). The relation between language and theory of mind in
development and evolution. In T. Givón & B. F. Malle (Eds.), The evolution of language out of pre-‐language, pp. 265-‐284, Amsterdam: Benjamins.
Massaro, D. W. (1998). Perceiving talking faces: From speech perception to a
behavioral principle. Cambridge, MA: MIT Press. McGurk, H., & MacDonald, J. (1976). Hearing lips and seeing voices. Nature, 264, 746-‐
7mc48. McManus, C. (2002). Right hand, left hand. London: Weidenfeld and Nicolson. McNeill, David. (2005). Thought, Imagery, and Language: How gestures fuel thought
and speech. Chicago: University of Chicago Press. Ming, X., Brimacombe, M., & Wagner, G. C. (2007). Prevalence of motor impairment
in autism spectrum disorders. Brain and Development, 29, 565–570. Mithen, S. (2011). Musicality and Language. In Tallerman, M. and Gibson, K. (eds.) The
Oxford Handbook of Language Evolution. Oxford: Oxford University Press. p. 296-‐298.
Morgan, G. (2005). Review of ‘The resilience of language: what gesture creation in
deaf children can tell us about how all children learn language.’Journal of Child Language, 32, pp. 925-‐928.
Myklebust, H. (1957). The Psychology of Deafness. New York: Grune and Stratton. Nelson, D. (2009). Piecing together the evidence. Unpublished ms, University of
Leeds. Newmeyer, F. J. (2000). ’On the Reconstruction of ‘Proto-‐World’ Word Order’ in The
Evolutionary Emergence of Language: Social Function and the Origins of Linguistic
46
Form, (Eds.) Knight, C., Studdert-‐Kennedy, M. & Hurford, J. Cambridge: Cambridge University Press, pp. 372–388.
Noonan, J. P., Coop, G., Alessi, J., et al. (2006). Sequencing and analysis of
Neanderthal genomic DNA. Science, 314, 1113–1118. Origgi, G. & Sperber, D. (2000). Evolution, communication and the proper function of
language. In: Evolution and the human mind, ed. P. Carruthers & A. Chamberlain, pp. 140–69. Cambridge: Cambridge University Press.
Özçaliskan, S. & Dimitrova, N. (2013). How gesture input provides a helping hand to
language development. Seminars in Speech and Language, 34(4), 227-‐236. Özcaliskan, S., & Goldin-‐Meadow, S. (2005). Gesture is at the cutting edge of early language development. Cognition, 96, 101-‐113. PBS NOVA. (2015). Hominidae Family Tree. [online]:
http://www.pbs.org/wgbh/nova/education/activities/3416_id_02.html [accessed April 10, 2015].
Penfield, W., & Roberts, L. (1959). Speech and Brain Mechanisms. Princeton:
Princeton University Press. Penn, D. C., Holyoak, K. J., & Povinelli, D. J. (2008). Darwin’s mistake: Explaining the
discontinuity between human and nonhuman minds. Behavioral and Brain Sciences, 31, 109–178.
Peter, B., Raskind, W. H., Matsushita, M., Lisowski, M., Vu, T., Berninger, V. W., et al.
(2011). Replication of CNTNAP2 association with nonword repetition and support for FOXP2 association with timed reading and motor activities in a dyslexia family sample. J. Neurodev. Disord. 3, 39–49. doi: 10.1007/s11689-‐010-‐ 9065-‐0.
Petitto, L.A. (2000). On The Biological Foundations of Human Language. In K.
Emmorey and H. Lane (Eds.) The signs of language revisited: An anthology in honor of Ursula Bellugi and Edward Klima. Mahway, N.J.: Lawrence Erlbaum Assoc. Inc.
Petitto, L. A., & Marentette, P. (1991). Babbling in the manual mode: Evidence for the
ontogeny of language. Science, 251, 1493–1496. Pika, S., Liebal, K., & Tomasello, M. (2005). Gestural communication in subadult
bonobos (Pan paniscus): Repertoire and use. American Journal of Primatology, 65, 39–61.
Pinker, S. (1994). The Language Instinct. New York: Morow.
47
Pinker, S. (2003). Language as an adaptation to the cognitive niche. In: Christiansen, M.H., Kirby, S. (Eds.), Language Evolution. Oxford: Oxford University Press, pp. 16–37.
Pinker, S. & Bloom, P. (1990). Natural language and natural selection.
Behavioral and Brain Sciences, 13, 707–784. Ploog, D. (2002). Is the neural basis of vocalisation different in non-‐human primates
and Homo sapiens? In: Crow, T.J. (Ed.), The Speciation of Modern Homo Sapiens. Oxford University Press, Oxford, pp. 121–135.
Pollick, A. S., and de Waal, F. B. M. (2007). Ape gestures and language evolution. Proc.
Natl. Acad. Sci. U.S.A. 104, 8184–8189. doi: 10.1073/pnas.07026 24104. Pollick, A.S., Jeneson, A., and de Waal, F.B.M. (2008). Gestures and multimodal
signalling in bonobos. In The Bonobos: Behavior, Ecology, and Conservation, (Eds.) T. Furuichi and J. Thompson, New York: Springer, pp. 75–94.
Premack, D. G. & Woodruff, G. (1978). ‘Does the chimpanzee have a theory of mind?’
Behavioral and Brain Sciences, 1(4):515-‐526. Richards, G. (1986). Freed hands or enslaved feet? A note on the behavioral
implications of ground-‐dwelling bipedalism. Journal of Human Evolution, 15: 43-‐50.
Rizzolatti, G. & Arbib, M. A. (1998). Language within our grasp. Trends in
Neuroscience, 21:188–94. Rizzolatti, G., & Craighero, I. (2004). The mirror-‐neuron system. Annual Review of
Neuroscience, 27, 169–192. Rizzolatti, G., Camarda, R., Fogassi, L., Gentilucci, M., Luppino, G., Matelli, M., (1988).
Functional organization of inferior area 6 in the macaque monkey. II. Area F5 and the control of distal movements. Experimental Brain Research, 71, 491–507.
Rizzolatti G., & Sinigaglia C. (2008). Mirrors in the brain. How our minds share actions
and emotions. Oxford: Oxford University Press. Rizzolatti, G. & Sinigaglia, C. (2010). The functional role of the parieto-‐frontal mirror
circuit: interpretations and misinterpretations. Nature Neuroscience, 11:264-‐274. Rizzolatti, G., Fogassi, L., & Gallese, V. (2001). Neurophysiological mechanisms
underlying the understanding and imitation of action. Nature Reviews, 2, 661–670. Roberts, A. I., Vick, S. J., and Buchanan-‐Smith, H. M. (2012). Usage and
comprehension of manual gestures in wild chimpanzees. Anim. Behav. 84, 459–470. doi: 10.1016/j.anbehav.2012.05.022
48
Roberts A. I., Vick, S. J., Buchanan-‐Smith, H. M. (2013). Communicative intentions in
wild chimpanzees: persistence and elaboration in gestural signaling. Anim Cogn 16: 187–196. doi: 10.1007/s10071-‐012-‐0563-‐1.
Rosenberg, K. R., & Trevathan, W. R. (2014). Evolutionary obstetrics.Evolution,
Medicine, and Public Health, 2014 (1), 148. doi:10.1093/emph/eou025. Rumbaugh, D. M. (1977). (Ed.) Language learning by a chimpanzee: The LANA project.
New York: Academic Press. Sandler, W., Meir, I., Padden, C. & Aronoff, M. (2005). The emergence of grammar:
Systematic structure in a new language. Proceedings of the National Academy of Sciences USA, 102(7):2661–65.
Sasaki, C.T., Levine, P. A., Laitman, J. T., Crelin, E. S.Jr (1977). Postnatal descent of the
epiglottis in man. Arch. Otolaryngol. 103, 169–171. Saussure, F. (1916). Nature of the Linguistic Sign. In C. Bally & A. Sechehaye (eds)
Cours de linguistique générale. McGraw Hill Education. Savage-‐Rumbaugh, S., Mirphy, J., Sevcik, R. A., Brakke, K. E., Williams, S. L.,
Rumbaugh, D. M., Bates, E. (1993). Language Comprehension in Ape and Child. Monographs for the Society for Research in Child Development, 58, 1-‐256.
Savage-‐Rumbaugh, S., Shanker, S. G., & Taylor, T. J. (1998). Apes, language, and the
human mind. New York: Oxford University Press. Scott, W. R. (1870).The Deaf and Dumb: their Education and Social Position, 2nd ed.
London: Bell & Daldy. Senghas, A. (1995). The Development of Nicaraguan Sign Language via the Language
Acquisition Process. In D. MacLaughlin & S. McEwen (eds.), Proceedings of the Boston University Conference on Language Development, 19, 543-‐552. Boston: Cascadilla Press.
Senghas, A. & Coppola, M. (2001). Children creating language: How Nicaraguan Sign
Language acquired spatial grammar. Psychological Science, 12, pp. 323–328. Slobin, D. I. (2004). From Ontogenesis To Phylogenesis: What Can Child Language Tell
Us About Language Evolution? In J. Langer, S. T. Parker, & C. Milbrath (Eds.) Biology and Knowledge revisited: From neurogenesis to psychogenesis. Mahwah, NJ: Lawrence Erlbaum Associates.
Smith, N. (1999). Chomsky: Ideas and ideals. Cambridge: Cambridge University Press. Sterelny, K. (2012). Language, gesture, skill: the co-‐evolutionary foundations of
49
language. Philosophical Transactions of the Royal Society, 367, 2141–2151. doi:10.1098/rstb.2012.0116.
Stokoe, W. C. (1960). Sign Language Structure: An Outline of the Visual Communication Systems of the American Deaf. Studies in linguistics: Occasional papers (No. 8). Buffalo: Dept. of Anthropology and Linguistics, University of Buffalo.
Stokoe, W. C. (2001). Language in Hand: Why Sign Came Before Speech. United
States: Gallaudet University Press. Tallerman, M. (2007). Did our ancestors speak a holistic protolanguage? Lingua, 117,
579-‐604. Tallerman, M. (2011). Protolanguage. In Tallerman, M. and Gibson, K. (eds.) The
Oxford Handbook of Language Evolution. Oxford: Oxford University Press, pp.479-‐491.
Tobias, P. (1998). ‘Evidence for the Early Beginnings of Spoken Language.’ Cambridge
Archaeological Journal, vol. 8, pp. 72-‐78. Tomasello, M. (2008). The Origins of Human Communication. Cambridge, MA: MIT
Press. Tzourio-‐Mazoyer, N. & Courtin, C. (2013). Brain lateralization and the emergence of
language. In New Perspectives on the Origins of Language (Eds.) Lefebvre, C., Comrie, B. and Cohen, H. Netherlands: John Benjamins Publishing Co.
van Driem, G. (2005) The language organism: The Leiden theory of language
evolution. In: Language acquisition, change and emergence: Essays in evolutionary linguistics, ed. J. Minett & W. Wang, pp. 331–40. City University of Hong Kong Press.
Vico G. B. (1953/1744). La Scienza Nuova. Bari: Laterza Vilain, A., Schwartz, J. L., Abry, C. and Vauclair, J. (2011). Primate Communication and
Human Language: Vocalisation, Gestures, Imitation and Deixis in Humans and Non-‐humans. Philadelphia: John Benjamins Publishing Co.
Walker, A. and Leakey, R. (1993). The postcranial bones. In The Nariokotome Homo
erectus skeleton, ed. A. Walker and R. Leakey, pp. 95-‐160. Springer: Berlin. Watkins, K. E., Vargha-‐Khadem, F., Ashburner, J., Passingham, R. E., Connelly, A.,
Friston, K. J., Frackowiak, R. S., Mishkin, M., Gadian, D. G. (2002). MRI analysis of an inherited speech and language disorder: structural brain abnormalities. Brain, 125, 452-‐464.
50
Werner, H., & Kaplan, B. (1963). Symbol formation. New York: Wiley. Williams, J. H. G., Whiten, A., Suddendorf, T. & Perrett, D. I. (2001). Imitation, mirror
neurons and autism. Neuroscience and Behavioural Reviews, 25:287– 95. Williams, J. H. G., Whiten, A. and Singh, T. (2004). A systematic review of action
imitation in autistic spectrum disorder. J. Autism Dev. Discord., 34 (3), 285-‐299. Xu, J., Gannon, P. J., Emmorey, K., Smith, J. F., & Braun, A. R. (2009). Symbolic
gestures and spoken language are processed by a common neural system. Pro-‐ ceedings of the National Academy of Sciences of the United States of America, 106, 20665–20669.
Zlatev, J. (2015). The Emergence of Gestures, in The Handbook of Language
Emergence (Eds.) B. MacWhinney and W. O'Grady, Hoboken, NJ, USA: John Wiley & Sons, Inc. doi: 10.1002/9781118346136.ch21.