Chapter 10

A Word in the Hand: The Gestural Origins

of Language

Michael C. Corballis

10.1  Introduction

The evolution of language, it has been suggested, may be “the hardest problem in
science” (Christiansen and Kirby 2003, p. 1). In 1866, shortly after the publication
of Darwin’s (1859) Origin of Species, it was so controversial that the Linguistics
Society of Paris banned all discussion of the origins of language, and shortly after-
wards the Philological Society of London followed suit. This seemed to create
something of a hiatus, and it was not really until around a century later that interest
picked up again. Even so, the topic remains highly contentious to the point that one
might wonder whether the ban should be reinstated. One widely held theory is
that held by the dominant linguist of our time, Noam Chomsky, and supported by a
number of archeologists and prehistorians. This theory might be termed the “big
bang” theory, since it holds that language emerged in a single step and was restricted
to our own species, Homo sapiens. In evolutionary terms this theory effectively
denies any evolutionary precursors and is nonspecific as to the mechanisms of evo-
lutionary change. In this chapter, I discuss this theory first, and suggest that it is
deeply implausible. I then go on to consider an evolutionary account that is in many
respects its opposite. In this alternative view language evolved from manual ges-
tures, and its origins go far back in primate evolution.

M.C. Corballis (*)

School of Psychology, University of Auckland, Auckland 1010, New Zealand
e-mail: m.corballis@auckland.ac.nz

© Springer Science+Business Media LLC 2017 199

M. Mody (ed.), Neural Mechanisms of Language, Innovations in Cognitive
Neuroscience, DOI 10.1007/978-1-4939-7325-5_10
200 M.C. Corballis

10.1.1  The “Big-Bang” Theory

Chomsky (2010) maintains that there were no languages prior to 100,000 years ago,
and that when language did emerge it was the outcome of a sudden event, perhaps a
mutation, in a single individual. This occurred in Africa sometime after 100,000 years
ago and was disseminated through the population prior to the dispersal of humans
from Africa some 60,000 years ago. In the most recent of Chomsky’s various for-
mulations, the essence of language and underlying thought is unbounded Merge, the
process whereby elements are merged in recursive fashion to create what Chomsky
has also called “discrete infinity”—the limitless number of possible structures that
can be formed. Unbounded Merge is the basis of what has also been termed univer-
sal grammar, the common grammatical core of all human languages.
This is a simple solution because it requires only a single event, and obviates the
need to seek precursors to language in other species, or even in our hominin ances-
tors. In part, its rationale follows from the very notion of unbounded Merge, which
according to Chomsky must have arisen in all-or-none fashion. Just as the notion of
infinity itself was not achieved by the ability to count to increasingly large numbers,
so it seems highly unlikely that unbounded Merge could be reached by gradually
extending the bounds on progressive Merge operations. As we shall see, though, this
conclusion can be challenged.
Nevertheless the big-bang theory receives independent support from evidence
that a “cultural revolution” took place in human prehistory within the past
100,000 years. It was characterized by the seemingly abrupt appearance of what has
been termed “modern” behavior, including the fashioning of bodily ornamentation
from shells, beads, or animal teeth, the emergence of sophisticated cave art, and a
sudden advance in the level of technology. Summarizing the evidence, the archae-
ologist Sir Paul Mellars concludes as follows:
To describe the Upper Paleolithic revolution in Europe as reflecting preeminently an explo-
sion in explicitly symbolic behavior and expression is in no sense an exaggeration, as most
prehistorians would now agree. We are probably on safe ground in assuming that symbolic
behavior and expression of this level of complexity would be inconceivable in the absence
of highly structured language systems and brains closely similar, if not identical to, our own
(Mellars 2005, p. 12).

Although this extract seems to imply that the revolution took place in Europe,
most now agree that its beginnings were evident in Africa prior to the dispersal, but
it is still argued that it occurred well after the appearance of anatomically modern
humans, dated at around 200,000 years ago (Marean 2010).
In a recent popular book Tattersall (2012) affirms that the cultural revolution did
indeed coincide with the big bang that gave us language:
Our ancestors made an almost unimaginable transition from a non-symbolic, nonlinguistic
way of processing information and communicating information about the world to the sym-
bolic and linguistic condition we enjoy today. It is a qualitative leap in cognitive state
unparalleled in history. Indeed, as I’ve said, the only reason we have for believing that such
a leap could ever have been made, is that it was made. And it seems to have been made well
after the acquisition by our species of its distinctive modern form (p. 199).
10  A Word in the Hand: The Gestural Origins of Language 201

In its apparent simplicity, though, the big-bang theory smacks of the miraculous.
The tone of the above extract does imply that there is no real precedent, nor any
clear explanation, for the “unimaginable transition.” Its rather biblical quality sug-
gests that it may have been driven as much by wishful thinking as by scientific evi-
dence. It serves, for example, to justify the manner in which we exploit other
animals, and perhaps exonerate us from the suspicion that our forebears may have
been responsible for the demise of our close but now extinct relatives the
Neanderthals and Denisovans, with whom we coexisted until some 30,000  years
ago.
More importantly, the big-bang theory is profoundly at odds with Darwin’s the-
ory of evolution by natural selection. Darwin himself wrote:
If it could be demonstrated that any complex organ existed, which could not possibly have
been formed by numerous, successive, slight modifications, my theory would absolutely
break down. But I can find no such case (Darwin 1859, p. 158).

If correct, then, the big-bang theory of language evolution might be the very case
that Darwin feared. Chomsky himself has often referred to language as “an organ of
the body” (e.g., Chomsky 2007, p. 5), at least comparable in complexity to, say, the
heart or liver. So far as we know, no such organ has emerged as a result of a single
mutation in a single individual.

10.1.2  The Case for Continuity

Pinker and Bloom (1990) wrote in support of a Darwinian account of language

evolution in a landmark article and included the following comment:
If a current theory of language is truly incompatible with the neo-Darwinian theory of evo-
lution, one could hardly blame someone for concluding that it is not the theory of evolution
that must be questioned, but the theory of language (p. 708).

As a first step, then, one can challenge the idea that language, by its very nature,
must have evolved in all-or-none fashion. Unbounded Merge is really an idealized
abstraction, since people do have limits on the extent to which they can merge lin-
guistic elements, whether in production or comprehension. One example of the
Merge operation is the embedding of clauses within sentences, as in The rat that the
cat killed ate the malt. We can push it to another level of embedding, as in The rat
that the cat that the dog chased killed ate the malt, although this borders on unintel-
ligibility. Yet another level taxes the system to an unacceptable degree: The rat that
the cat that the dog that the cow worried chased killed ate the malt. Contrary to the
notion of unbounded Merge, Fujita (2009), among others, has proposed a gradual
evolution of Merge through progressive levels of recursion. Moreover some lan-
guages, such as those of the Pirahã in Brazil (Everett 2005) and the Iatmul of New
Guinea (Evans 2009), appear to have no recursive embedding at all. The sheer diver-
sity among the world’s 7000 or so languages has led several to claim that the very
202 M.C. Corballis

notion of universal grammar, as proposed by Chomsky, has no validity (e.g.,

Christiansen and Kirby 2003; Evans and Levinson 2009; Tomasello 2008).
The evidence for the cultural revolution underlying the big bang has also been
challenged. Marean et al. (2007) report evidence for “modern” human activity going
back 160,000 years, close to the date at which H. sapiens emerged and well before
the supposed big bang. McBrearty and Brooks (2000) write of the “revolution that
wasn’t,” suggesting a more gradual rise in technological sophistication from the
Middle Stone Age around 250,000–300,000 years ago. More recently Shea (2010)
has argued that the apparent spurt of technology supposedly evident in Africa in the
Middle Paleolithic was more likely a phase that came and went, an indication of
variability rather than a sudden and universal shift toward greater sophistication. In
much more recent times, the colonizers of the Americas or the European explorers
in Africa found little if anything to resemble the burst of symbolic behavior in the
Upper Paleolithic, as described by Mellars (2005).
A corollary of the big-bang theory is that the Neanderthals and Denisovans
would not have possessed the faculty of language. These large-brained hominins all
shared a common ancestor with H. sapiens dating from some 500,000 years ago,
and were separated from around 400,000  years ago, with the lineages leading to
Neanderthals and Denisovans in Europe and that leading to modern humans con-
fined to East Africa until the dispersal from around 60,000 years ago. The wander-
ing humans eventually made contact with their long-lost cousins in Europe and
Russia from around 40,000 years ago. Sequencing of both the Neanderthal (Green
et al. 2010) and Denisovan (Meyer et al. 2012) genomes reveals a degree of inter-
breeding both with each other and with anatomically modern humans. This suggests
in turn that the three species had common cognitive capacities, and indeed raises
questions as to whether they were different species (Reich et al. 2010). At worst, the
Neanderthals and Denisovans might have had some linguistic deficiencies relative
to H. sapiens, but not the total lack implied by the big-bang theory.
Several arguments have been mounted to show that Neanderthals were incapable
of language, but have proven far from definitive (see Johansson 2013 for review).
Suggestions that the Neanderthal vocal tract could not sustain articulate speech
(e.g., Lieberman 2007) have proven at best inconclusive (e.g., Barney et al. 2012;
Boë et al. 2007). A mutation of the FOXP2 gene resulted in a severe speech impedi-
ment in about half the members of an extended English family, leading to sugges-
tions that a (different) mutation of this otherwise highly conserved gene may have
occurred in the human lineage to enable speech (Enard et al. 2002). This appears to
have been refuted by the discovery that the region on the human version of the gene
thought to be critical was present in Neanderthal DNA (Krause et  al. 2007)—
although the human FOXP2 may still differ in other ways (Ptak et al. 2009).
The question of whether or not the Neanderthals were capable of articulate
speech in any case need not bear on the broader question of whether they were
capable of language. Even in Chomskyan theory, the internal basis of language is
symbolic and amodal; external language (E-language) interfaces with I-language,
and can be expressed either vocally or manually, or a mixture of the two. Indeed, it
may well be that external language was first expressed through gesture rather than
10  A Word in the Hand: The Gestural Origins of Language 203

speech, and the Neanderthals communicated in language-like ways with their hands
rather than their voices—or more likely both. In the following sections I argue that
language did evolve from manual gestures, although the transition to speech was
probably gradual, and indeed incomplete.

10.2  The Gestural Theory

Speculation that language evolved from manual gestures has a long history. One
early proponent was the philosopher and cleric de Condillac (1971). He was an
ordained priest, and was afraid of offending the Church’s view that language was a
gift from God, so he disguised his theory as a fable about two children abandoned
in the desert after the Flood. At first they communicated by using bodily move-
ments, until eventually replacing their gestures with vocal sounds. Over the suc-
ceeding centuries many others have made similar suggestions as to the priority of
manual gesture, including such dominant figures as Rousseau (1782), Wundt (1900),
and the neurologist Critchley (1939, 1975).
A more comprehensive case for gestural origins was proposed by Hewes et al.
(1973), and set the stage for subsequent developments (e.g., Arbib 2005; Corballis
1991, 2002; Rizzolatti and Sinigaglia 2008; Tomasello 2008). It presents a very dif-
ferent perspective on language evolution from the big-bang theory.

10.2.1  The Primate Mirror System

A convenient starting point, but one unknown to Hewes, was the discovery of mirror
neurons in area F5 of the rhesus monkey (Rizzolatti et al. 1988). Area F5 is a region
in the prefrontal cortex homologous to Broca’s area in the human brain. Mirror
neurons are so called because they are active not only when the animal executes a
hand movement to grasp an object, but also when it observes another individual
making the same movement. They therefore represent a mapping, or mirroring,
between perception and action, thereby suggesting an evolutionarily early template
for the later emergence of a communication system. Mirror neurons are now under-
stood to be part of a more general mirror system, incorporating the superior tempo-
ral sulcus and area PF in the inferior parietal lobule (Rizzolatti and Sinigaglia 2010).
Area PF is homologous to part of Wernicke’s area in the human brain.
It is now known too that the homologous areas in humans mediate sign language,
as well as symbolic gestures such as pantomimes and emblems (e.g., Xu et  al.
2009). Mirror neurons tuned to manual grasping, whether executed or observed,
have also been confirmed from single-cell recordings in humans with intractable
epilepsy and were located in a variety of areas, including medial frontal and tempo-
ral regions (Mukamel et al. 2010).
204 M.C. Corballis

Arbib (2005) has speculated in detail as to how language might have evolved
from the mirror system. In primate evolution, he suggests, the mirror system pro-
gressed from a system for grasping to one that included imitation, and from there to
a system supporting sequences of actions, enabling pantomime. This was then the
substrate for what Arbib called “protosign,” an open-ended system of signs, but
without the combinatorial, syntactic structure of language. This in turn provided a
scaffold for protospeech, which up to that stage owed little to nonhuman vocaliza-
tions. From that point, an “expanding spiral” of protosign and protospeech led to
true language, whether spoken or signed. While this seems a plausible scenario, it is
also possible that gestural language evolved to a syntactic level similar to that of
modern signed languages before vocalization was introduced. Tomasello (2008), for
example, writes of the possibility “that the human capacity evolved quite a long way
in the service of gestural communication alone, and the vocal capacity is actually a
very recent overlay (p. 246).”
In this view, then, the origins of language lie in a system initially dedicated to
manual grasping, and indeed the concept of grasping underlies many expressions to
do with language itself. The word grasp is often used to mean “understand.”
Comprehend and apprehend derive from Latin prehendere, “to grasp”; intend, con-
tend, and pretend derive from Latin tendere, “to reach with the hand”; we may press
a point, and expression and impression also suggest pressing. We hold conversa-
tions, point things out, seize upon ideas, grope for words. It works visually, too, as
when you see what somebody means. Fonagy and Target (2007, p. 437) suggest that
such examples are indeed “a residue of gestural language.”
To contribute to communication, the mirror system in nonhuman primates
required at least one further modification. Mirror neurons in primates are transitive
in that they respond only to actions involving the grasping of an actual object, even
if that object is hidden behind a screen but the animal knows it is there (Umilta et al.
2001). In humans, evidence from neuroimaging suggests that the mirror system
responds as well to intransitive actions, where a movement occurs in the absence of
an object to be grasped. This suggests that the human mirror system was extended
to incorporated actions that were symbolic along with those that were object related.
This may have come about, not through a “big bang” mutation providing for sym-
bolic representation, but from the requirement of language to refer to events not
present in the here-and-now (Corballis 2009). This is almost tangible in American
Sign Language where, in conversation, absent objects are notionally “placed” at
different locations in front of the speaker, and reference to those objects is achieved
by pointing to the appropriate location (Emmorey 2001). Speakers often point in a
similar way when they gesture as they talk (Kendon 2004).
In nonhuman primates, the mirror system does not respond to vocalization
(Rizzolatti and Sinigaglia 2008), which probably reflects the involuntary nature of
primate vocalization. This is a further reason to suppose that language evolved from
manual actions, since language is an intentional system. Kohler et al. (2002) found
mirror neurons in monkeys to be receptive to nonvocal acoustic input, including the
sounds of manual acts such as tearing paper or cracking peanuts, but there was no
response to monkey calls. In humans, perhaps uniquely, vocalization does appear to
10  A Word in the Hand: The Gestural Origins of Language 205

have been incorporated into the mirror system and at the same time become
amenable to volition. This may have required a direct connection between the motor
cortex and the nucleus ambiguus, the subcortical structure responsible for the coor-
dinated movements involved in speech (Jürgens 2002).
The incorporation of vocalization into the mirror system is captured in the motor
theory of speech perception, which holds that speech sounds are perceived in terms
of how they are articulated rather than in terms of their acoustic properties (e.g.,
Galantucci et al. 2006). Nevertheless the motor theory does not completely explain
speech perception. Hickok (2009) points out that people with Broca’s aphasia lose
the ability to produce articulate speech yet can still understand it, and human infants
also understand words before they can produce them. However, in a recent paper
revisiting the perception of the speech code, Fowler et al. (2016) clarify that pho-
netic segments are articulatory and coarticulation does not eliminate them; rather,
phonetic segments appear to leave an acoustic signature that listeners can track.

10.2.2  Dual-Stream Theory

Hickok and Poeppel (2007) have suggested a “dual-stream” account of speech pro-
cessing in humans, with a ventral stream for comprehension and a dorsal stream
mapping onto the frontal-lobe articulatory networks. It is only the dorsal stream,
then, that involves the mirror system, one role of which is to shape action to be
compatible with input. In nonhuman primates, this role is well advanced for manual
action, but not for vocal output. In humans, though, the mirror system appears to
incorporate vocal production, and allow for productive language to emerge in the
vocal modality. Both dorsal and ventral systems, moreover, appear to be involved in
syntax, in different ways.
Van der Lely and Pinker (2014) draw attention to a subtype of specific language
impairment (SLI) in which the primary deficit is grammatical. Children with this
subtype, known as Grammatical-SLI, are especially deficient in processing complex
grammatical constructions. To account for this deficiency, van der Lely and Pinker
distinguish between basic and extended syntax. Basic syntax connects words to
meanings, and deals with short-range syntax, as in words in which tense is conveyed
in the word as a whole, such as the English irregular past-tense forms “ate” or
“bought.” Basic syntax is represented in the ventral system and may be sufficient for
what has been termed protolanguage—language without combinatorial syntax.
Extended syntax is combinatorial, as in the merging of morphemes to represent past
tense (“jumped,” “climbed”) or in more complex cases where understanding may
depend upon integrating across different words, as in sentences where subject and
verb are separated by intervening clauses. Extended syntax depends on the dorsal
system, left-hemispheric in most people, and involves interaction between lateral
frontal cortex and basal ganglia (Mestres-Missé et al. 2012).
A possibly related dissociation may occur in sign language. Hickok et  al.
(2009) showed that when narrating a story in American Sign Language, signers
206 M.C. Corballis

with ­left-­hemisphere damage make more lexical than classifier errors, whereas
right-­hemisphere damage results in the reverse pattern. Lexical signs signal rela-
tions in categorical form, where classifier signs are more analogue in character,
and of debatable linguistic status. The authors suggest that the production of lexi-
cal signs is strongly left-hemispheric, whereas producing classifier forms relies
on both hemispheres. In this study the brain damage was located primarily in
fronto-parietal regions, and in two cases the left-hemisphere damage, resulting
primarily in lexical errors, was in the basal ganglia. Again, then, it may be the
left-hemispheric dorsal system, which includes the basal ganglia, that underlies
the grammatical component, and that emerged from the primate mirror system.

10.2.3  The Role of Learning

Language is not only intentional, it also requires learning. Each of the some 7000
different languages in the world requires a distinctive set of outputs to be learned.
Of course most of these languages are spoken, requiring the learning of vocal pat-
terns. Although vocal communication is widespread in the animal kingdom, surpris-
ingly few species are capable of vocal learning. Nonhuman primates are
conspicuously absent from the list, which includes elephants, seals, killer whales,
and some birds (Jarvis 2006). Jürgens (2002) links failure of vocal learning to the
absence of cortical representation:
As the vocalizations of monkeys, cats, and bats are almost completely genetically deter-
mined in their acoustic structure, while the vast majority of human vocalizations are more
or less completely learned, the difference in cortical representation might reflect the differ-
ent role motor learning plays in vocal behavior of these species (p. 246).

Jarvis and Jürgens concur that among the existing primates, only humans are
vocal learners.
Nevertheless some studies suggest a degree of modifiability in some primate
calls, although this may have to do with subtle changes within call types rather than
the generation of new call types (Egnor and Hauser 2004). Chimpanzees modify
their screams when under attack, depending on the severity of the attack and their
status relative to that of nearby chimps (Slocombe et al. 2010). When encountering
food, chimps also emit different kinds of grunts depending on the type of food
(Slocombe and Zuberbühler 2005). Some modifications involve the face and mouth
rather than voicing itself. For instance chimpanzees can modify vocal sounds to
attract attention by vibrating their lips, as in the “raspberry” sound (Hopkins et al.
2007), and this call can be imitated by naïve animals in captivity (Marshall et al.
1999).
In a recent review Petkov and Jarvis (2012) suggest that the distinction between
vocal learners and vocal nonlearners may not be absolute, but may be a matter of
degree. The extraordinary capacity of humans to learn complex and vastly different
speech patterns is nevertheless well beyond that of any other known primate. It would
10  A Word in the Hand: The Gestural Origins of Language 207

not be surprising, though, if precursors of vocal learning did exist in our more recent
primate forebears, since evolutionary change does not emerge out of nothing. Even
so, there seems little doubt that the capacity to learn manual patterns of activity goes
far back in primate evolution.

10.2.4  Communication in Great Apes

The clearest evidence that intentional manual action moves beyond grasping to
serve an intentional communicative function in nonhuman primates comes from the
great apes. No attempt to teach apes to speak has proven even remotely successful
(e.g., Hayes 1951; Kellogg and Kellogg 1933; Ladygina-Kohts et  al. 2002), but
moderate success has been achieved using forms of sign language. One of the first
to achieve some success was the chimpanzee Washoe, using a simplified form of
American Sign Language (Gardner and Gardner 1969). More impressive is the
bonobo Kanzi, who communicates by pointing to arbitrary signs representing
objects and actions to make simple requests (Savage-Rumbaugh et al. 1998). The
keyboard Kanzi uses has over 300 signs, and he supplements these by inventing
gestures of his own. The gorilla Koko is said to use and understand over 1000 signs
(Patterson and Gordon 2001).
These examples are somewhat artificial, since they are drawn from animals in
artificial settings created by humans, but observations of apes in the wild also sug-
gest a dominance of bodily over vocal communication, especially where communi-
cation is intentional rather than emotional or instinctive. Pollick and de Waal (2007)
compared manual gestures directly with orofacial movements and vocalizations in
the natural communications of captive chimpanzees and bonobos, and found man-
ual gestures to be much less tied to context, and more variable between groups. The
relative flexibility of manual gestures was more pronounced in bonobos than in
chimpanzees, and only in bonobos did the combining of facial and vocal signals to
manual gestures add to the impact on the recipient. This study is not definitive with
respect to intentional control over vocalization, since vocalizations were lumped
together with orofacial movements, and many such movements in chimpanzees and
bonobos, such as lipsmacks, are not vocalized, but may well be under intentional
control. This study nevertheless confirms the dominance of manual gesture in the
natural communications of our closest nonhuman relatives.
In perhaps the most comprehensive study of chimpanzee gestures in the wild,
Hobaiter and Byrne (2011) spent 266 days of recording gestures made by chimpan-
zees in the Budongo National Park in Uganda. Gestures included movements of the
body, limbs, and head, but excluded facial expressions. They were intentional in that
they were directed to another chimp, with the apparent aim of influencing the receiv-
er’s behavior, and they were also described as “mechanically ineffective,” presum-
ably to exclude acts like fighting, eating, or manipulation of objects. They included
actions like a directed push, a handshake, an embrace, sexual display, and what has
been called the “directed scratch,” in which the chimp scratches the part of the body
208 M.C. Corballis

where he or she wants to be groomed by another chimp (Pika and Mitani 2009). It
has been suggested that grooming itself is precursor to language (Dunbar 1998).
A total of 4397 gestures were recorded, made up of at least 66 different kinds of
gestures. Most were recorded during play, but others occurred during other activi-
ties, such as grooming, travelling, or feeding. Just over 60% of them were single
gestures, but others occurred in bouts, most commonly made up of two gestures, but
in sequences of three, four, or at most five, with decreasing frequency. These bouts
did not seem to resemble sentences in any way. Instead they seemed to be largely
redundant, as though trying to get a single point across in different ways.
It has also been proposed that tool making is a precursor to language (Stout and
Chaminade 2012), and there are well documented examples of chimpanzees mak-
ing and using tools. They fashion sticks for fishing termites out of holes (Bogart and
Pruetz 2008) and make spears for jabbing into the hollow trunks of trees to extract
bush-babies and then eat them (Pruetz and Bertolani 2007). Chimpanzees in the
Laongo National Park in Gabon use tool sets comprising up to five different stick
and bark tools to extract honey from hives (Boesch et al. 2009). Some 25 different
kinds of chimpanzee tools have been documented.
Of course chimpanzees do vocalize, but their vocalizations are largely involun-
tary, perhaps even exclusively so. Premack (2007), a pioneer in the study of chim-
panzee behavior, notes that “chimpanzees lack voluntary control of their voice”
(p.  13,866). Another pioneering observer of chimpanzees once wrote that “(t)he
production of sound in the absence of the appropriate emotional state seems to be
an almost impossible task for a chimpanzee” (Goodall 1986, p.125). By the same
token, emotionally induced primate vocalization may be difficult to suppress.
Goodall writes of a chimpanzee trying to stifle a call induced by the discovery of
food by placing a hand over his mouth—evidence of the intentional dominance of a
manual gesture over an involuntary vocal call. The capacity for intentional control
of the voice, largely absent in the chimpanzee, must therefore have evolved after the
separation of the hominin line from that leading to modern chimpanzees.

10.2.5  Understanding of Speech, Without Production

Even great apes, then, seem incapable of producing speech-like sounds, but some
have shown remarkable ability to understand speech. Savage-Rumbaugh et  al.
(1998) reported that Kanzi was able to follow instructions, made up of several spo-
ken words, at a level comparable to that of two-and-a-half-year-old child. Kanzi is
now said to understand some 3000 words (Raffaele 2006). The gorilla Koko, too,
can respond meaningfully to simple spoken requests, but cannot produce anything
resembling speech (Patterson and Gordon 2001). The ability to recognize spoken
words, and even to understand combinations, is not restricted to apes. A border col-
lie known as Rico responds accurately to spoken requests to fetch different objects
from another room and then either to place the designated object in a box or to bring
10  A Word in the Hand: The Gestural Origins of Language 209

it to a particular person (Kaminski et al. 2004). In what is shaping as a linguistic dog

fight, another border collie called Chaser is said to know the spoken names of 1022
objects (Pilley and Reid 2011).
These observations support Hickok and Poeppel’s suggestion of a ventral system
of vocal understanding not involving the mirror system. What chimpanzees and
dogs lack is not the ability to understand symbols, but rather the ability to produce
vocalizations to act as symbols, as well as the capacity for extended syntax. Their
ability to understand spoken words may derive from the need to respond to complex
sounds, whether emanating from the calls of other animals or from other environ-
mental events, such as thunder or the sound of a tree falling—or the sound of another
species. In short, the auditory system may well have been pre-adapted for the recep-
tive aspects of language well before our forebears were able to produce language-­
like sounds. It is with respect to the production of language, then, that the vocal
system in nonhuman species falls short, suggesting that language evolved initially
within the visuo-manual mode, which was already preadapted for both the percep-
tion and production of intentional acts.
The ability of apes and dogs to respond meaningfully to spoken commands also
suggests that symbolic representations are not restricted to humans, as implied by
the big-bang theory, and indeed by those authors cited earlier who suggest that a
cultural revolution occurred because of a new-found symbolic understanding. The
burden of understanding the evolution of human language falls not on how symbols
were invented, but rather on how output systems evolved to create intentional sig-
nals—and perhaps also on how these systems evolved the combinatorial capacity to
create complex meaning.

10.2.6  Human Gestures

Part of the argument that language evolved from gesture is that the hands play an
important but often neglected role in the way people communicate. As long ago as
the first century AD, the Roman rhetorician Quintilian wrote:
As for the hands, without which all action would be crippled and enfeebled, it is scarcely
possible to describe the variety of their motions, since they are almost as expressive as
words (Quintilian 1920, pp. 290–291).

It has also long been known that signed languages can serve in place of speech,
especially among the deaf and mute, as well as in some speaker-hearer communi-
ties, notably in aboriginal Australia (Kendon 2004) and among some native North
American groups (Mithun 1999).
It was not really until the mid-twentieth century, though, that sign language was
understood to be the equal of spoken language in grammatical and semantic sophis-
tication, and even the manual equivalents of phonology (Emmorey 2001), to the
point that American Sign Language (ASL) was declared to be the official language
of Gallaudet University, a university for the deaf in Washington DC.  This was
210 M.C. Corballis

largely due to William C.  Stokoe, who taught at Gallaudet and persuaded the
university to switch from oral methods. Stokoe used his understanding and knowl-
edge of sign language to argue that language evolved from manual gestures
(Armstrong et al. 1995; Stokoe 2001).
The very nature of sign language provides clues as to how language might have
emerged. The hands provide a natural medium for representing objects and actions
in the world, with the movement of the hands and arms describing trajectories and
the hands taking the shapes of objects. Emerging sign languages typically begin
with pantomime, but signs are then conventionalized so that many no longer provide
a pictorial indication of what they stand for (Burling 1999). Conventionalization
may be at the cost of transparency, but leads to great efficiency. On an evolutionary
scale, speech itself may be the end product of a conventionalization process that
began with pantomime.
The distinction between speech and gestural communication is in any case not
absolute, since speech is universally accompanied by manual gestures, and the tight
synchrony between the two suggests that they are controlled by a single integrated
system (McNeill 1985). Experiments show that gestures influence the understand-
ing of speech, just as speech influences the understanding of gestures, an interaction
that is mutual and obligatory. Describing these results, Kelly et al. (2009) remark
that speech and gesture are “two sides of the same coin.” Modern language ranges
from pure speech, as on radio or telephone, to pure manual gesture, as in signed
languages, with conversational language somewhere in between. Moreover, if pre-
vented from speaking, people naturally invent gestural schemes, which can take on
grammatical properties (Goldin-Meadow et al. 1996).
The co-occurrence of manual gesture and speech, and perhaps the evolutionary
transition of dominance from one to the other, can be understood more readily if
speech itself is regarded as a gestural system, comprising movements of the lips, the
larynx, the velum, and the blade, body and root of the tongue (Studdert-Kennedy
2005). In the course of evolution, intentional communication may have evolved
from manual gestures, to overt facial gestures, and finally to the largely hidden ges-
tures that comprise speech—although all three forms of gesture remain present.
Speech gestures, although largely contained within the mouth, retain a visible com-
ponent, as illustrated by the McGurk effect: A syllable (such as da) is dubbed onto
a mouth saying another syllable (such as ba), and people tend to “hear” what they
see rather than what was actually voiced (McGurk and MacDonald 1976). Other
studies show the parts of the brain involved in producing speech are activated when
people simply watch silent videos of people speaking (Calvert and Campbell 2003;
Watkins et al. 2003). Ventriloquists know the power of vision over what one hears
when they project their own voices onto the face of a dummy by synchronizing the
mouth movements of the dummy with their own tight-lipped utterances.
The retreat of gestures into the mouth may be regarded as an early example of
miniaturization, freeing the hands and the rest of the body for other activities.
10  A Word in the Hand: The Gestural Origins of Language 211

10.2.7  Handedness and Brain Asymmetry

Among the arguments mounted by Hewes et al. (1973) for the gestural origins of
language was the coincidence of handedness and brain asymmetry:
The peculiarly human association of right-handedness and left-hemisphere dominance for
both language skill and precise manual manipulations could well be the outcome of a long
selective pressure for the clear separation of the precision grip from the power grip, com-
bined with a manual-gesture language exhibiting a similar (and related) asymmetry (p. 9).

Most people are indeed right-handed and left-cerebrally dominant for speech,
although some individuals are left-handed or right-cerebrally dominant for speech.
The correlation, though, is actually fairly weak (Badzakova-Trajkov et al. 2010),
perhaps because handedness, in particular, is subject to random influences (Annett
2002; McManus 2002).
These asymmetries appear to be present in the chimpanzee, although they are
less pronounced than in humans. Evidence suggests that a majority of chimpanzees
are right-handed, both in captivity (Hopkins 1996; Hopkins and Leavens 1998) and
in the wild (Biro et al. 2006; Boesch 1991; Humle and Matsuzawa 2009; Lonsdorf
and Hopkins 2005), although the incidence is round 65–70%, lower than the 90%
incidence in humans. Moreover, in the majority of chimpanzee brains, the temporal
planum, considered partly homologous to Wernicke’s area in humans, is larger on
the left than on the right (Gannon et al. 1998; Hopkins et al. 1998)—and asymmetry
apparently absent in rhesus monkeys and baboons (Wada et al. 1975) but well docu-
mented in humans (e.g., Foundas et al. 1996). This leftward asymmetry in the chim-
panzee is correlated with a right-handed bias in gestural communication (Hopkins
and Nir 2010).
Since the leftward bias is evident in great apes and is associated with manual
actions and not with vocal output, it again supports a priority for manual gesture
rather than vocal calls in the evolution of language. Evidence also reveals that, in
humans, the cortical control of skilled manual action, or praxis, is biased to the left
hemisphere in both left- and right-handers, suggesting a stronger relation to lan-
guage asymmetry than handedness itself (Vingerhoets et al. 2012). This further sup-
ports the idea that language evolved within a system specialized for manual control
of skilled movement that was already biased toward the left hemisphere (Corballis
et al. 2012).

10.2.8  Priority of Gesture in the Development of Language

It has become increasingly apparent that gesture comes before speech in the devel-
opment of language in human children. Of course, the adage that “ontogeny reca-
pitulates phylogeny,” attributed to Ernst Haeckel, has been largely discredited
(Gould 1977), but the sequence of events in the development of language can nev-
ertheless provide clues as to how language might have come about in evolution.
212 M.C. Corballis

In infants, intentional communication with manual gestures is evident from as

early as 10 months. Pointing is especially dominant early on and is used both to
request things, and to express attention to things (Tomasello 2008). Spoken words
are gradually introduced, but even at 16 months of age manual gestures are more
frequent. By 20 months, the balance has shifted, and spoken words become slightly
more frequent. The most frequent two-word utterances, though, nearly always com-
bine a gesture and a word, and it is not until later that two-word utterances are
composed of two spoken words (see Capirci and Volterra 2008 for review). Manual
gestures in early childhood can also predict later language success even up to the
two-word level (Iverson and Goldin-Meadow 2005).
Even in 1-year-olds, pointing seems to have a property that is unique to humans.
Chimpanzees can point to objects that are out of reach, with the aim of having a
person hand the object to them, but virtually all of these pointing gestures are impera-
tive, aimed at gratification. In contrast, 1-year-old children can point with the appar-
ent objective of sharing information, rather than of gaining reward. Tomasello (2008)
gives a number of examples where the intention is to share rather than request grati-
fication. A 13-month-old child watches as her father arranges the Christmas tree. Her
grandfather then enters and the child points to the tree for him, as if to say “Look!”
At 13.5  months, while her mother is looking for a missing refrigerator magnet, a
child points to a basket of fruit, under which the magnet is hidden.
Gestures therefore precede speech in development and serve to scaffold the
development of speech. One might conjecture that gesture played a similar role in
the evolution of language. Indeed, the role of gesture may have been even more
critical in language evolution, since the early hominins, unlike human infants, may
have been more severely lacking in the capacity to produce intentional
vocalization.

10.3  An Evolutionary Scenario

The seed for language may have been sown by the development of intentional man-
ual action in our primate forebears. These animals lived in forested environments
where the hands were extensively employed in climbing and swinging from
branches, as well as in such activities as plucking fruits, catching insects, and
grooming. The mirror system evolved to map the perception of these actions onto
their production. Although it has also been suggested that the mirror system evolved
primarily to mediate imitation (e.g., Rizzolatti and Craighero 2004), monkeys are
poor imitators, and the system probably had more to do with shaping action to con-
form to perception. Even plucking a piece of fruit requires the act to be conducted
in accordance with perception, and the mirror system may have emerged primarily
to mediate the monkey’s calibration of its own actions, rather than those of another.
Nevertheless the system does respond to actions of other individuals, perhaps
more by extension than original design, laying the groundwork for intentional
­communication. In great apes, the intentional motor system seems developed to the
10  A Word in the Hand: The Gestural Origins of Language 213

point of tool use and manufacture, as well as gestural communication. In interactions

with humans, at least in artificial settings, their gestures have some language-­like
properties, including a degree of combinatorial capacity, reference to nonpresent
objects, and the construction and understanding of simple commands. It is widely
agreed that no great ape has yet demonstrated true grammatical language, although
this view is at least partly dependent on Chomskyan views on the nature of lan-
guage. Even so, there is little evidence from chimpanzees or bonobos of a Merge
operation, unbounded or not.
The emergence of bipedalism in hominins probably enhanced the complexity of
gestures as well as of the use and manufacture of tools. The critical phase was prob-
ably the Pleistocene, dating from around 2.9 million to about 12,000 years ago. The
Pleistocene saw the beginning of a tripling of brain size, the emergence of stone
tools, and obligate replacing the more facultative bipedalism of the earlier homi-
nins. The Pleistocene is also widely recognized as the period in which hominins
came to occupy what has been termed the “cognitive niche” (Tooby and de Vore
1987), depending on social bonding and enhanced communication for survival in
the more exposed and dangerous environment of the African savanna. It seems
highly likely, then, that grammatical language evolved gradually during this era,
rather than late and abruptly, as implied by the big-bang theory.
As Donald (1991) argued, language probably emerged from pantomime, using
the body to mimic space-time activities and so convey them to a watching audience.
Pantomime, though, is inefficient, and over the course of the Pleistocene, the pres-
sure toward a more efficient and compact system may have driven the process of
conventionalization. Iconic or pantomimic gestures were replaced by simpler sig-
nals whose meanings were acquired through association rather than through picto-
rial representation. Meaning is then carried through cultural transmission, rather
than in the signal itself. Such signals might be described as arbitrary symbols, but
their arbitrary nature arose from practical concerns rather than from some new-­
found cognitive capacity—recall that chimpanzees and border collies can learn to
associate spoken words with objects and actions. As I suggested earlier, speech
itself might be regarded as an end result of progressive conventionalization.
Speech carries other advantages unrelated to conventionalization per se. While
gesturing can be physically exhausting, the physiological costs of speech are so low
as to be nearly unmeasurable (Russell et al. 1998). Speech adds almost nothing to
the energetic cost of breathing, which we must do anyway to sustain life. Speech
also frees the hands and body for other activities, such as manufacture and tool use,
and allows us to verbally explain manufacturing techniques while at the same time
demonstrating them physically. Indeed, it may have been this that led to a surge in
creative artifacts that some described as the cultural revolution of the middle to late
Pleistocene (Corballis 2004). Even so, we should not forget that manual gestures
still play an important role in human language, and the signed languages of the deaf
lose very little, if anything, in linguistic terms compared to speech.
214 M.C. Corballis

With the increasing importance of the mouth, gestures may have begun to retreat
inside the mouth, involving the tongue, lips, and eventually the larynx. Such ­gestures
are largely invisible, and recovered through the addition of sound, which is modu-
lated by internal gestures. In short, speech is facial gesture, half swallowed.1

Acknowledgments  I owe thanks to many people, including (but not restricted to) Michael Arbib,
Giovanni Berlucchi, Louis-Jean Boë, Tecumseh Fitch, Greg Hickok, William Hopkins, Nicholas
Humphrey, James Hurford, Adam Kendon, Maurizio Gentilucci, Russell Gray, Susan Goldin-­
Meadow, David Leavens, Giacomo Rizzolatti, Thomas Suddendorf, and Virginia Volterra.

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