Table Of ContentHow the Brain Got Language
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Oxford Studies in the Evolution of Language
General Editors
Kathleen R. Gibson, University of Texas at Houston,
and James R. Hurford, University of Edinburgh
PUBLISHED
1 9
The Origins of Vowel Systems The Genesis of Grammar
Bart de Boer Bernd Heine and Tania Kuteva
2
10
The Transition to Language
The Origin of Speech
Edited by Allison Wray
Peter F. MacNeilage
3
11
Language Evolution
The Prehistory of Language
Edited by Morten H. Christiansen
Edited by Rudolf Botha and
and Simon Kirby
Chris Knight
4
Language Origins 12
Perspectives on Evolution The Cradle of Language
Edited by Maggie Tallerman Edited by Rudolf Botha and
Chris Knight
5
The Talking Ape 13
How Language Evolved Language Complexity as an
Robbins Burling Evolving Variable
Edited by Geoffrey Sampson,
6
David Gil, and Peter Trudgill
Self-Organization in the Evolution
of Speech
14
Pierre-Yves Oudeyer
The Evolution of Morphology
Translated by James R. Hurford
Andrew Carstairs McCarthy
7
15
Why We Talk
The Origins of Grammar
The Evolutionary Origins of
Language in the Light of Evolution 2
Human Communication
James R. Hurford
Jean-Louis Dessalles
Translated by James Grieve
16
8 How the Brain Got Language:
The Origins of Meaning The Mirror System
Language in the Light of Evolution 1 Hypothesis
James R. Hurford Michael A. Arbib
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How the Brain Got
Language
The Mirror System Hypothesis
Michael A. Arbib
Computer Science, Neuroscience, and the USC Brain Project
University of Southern California
1
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3
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Library of Congress Cataloging-in-Publication Data
Arbib, Michael A.
How the brain got language : the mirror system hypothesis / Michael A. Arbib.
p. cm.
Includes bibliographical references and index.
I SBN 978-0-19-989668-4 (hbk . : acid-free paper)
1. Brain–Evolution. 2. Brain–Anatomy. 3. Language and languages–Origin.
4. Mirror neurons. 5. Evolutionary psychology. 6. Neurolinguistics.
7. Macaques–Anatomy. 8. Anatomy, Comparative. I. Title.
QP399.A73 2012
612.8'2—dc23
2011047813
9 8 7 6 5 4 3 2 1
Printed in the United States of America
on acid-free paper
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To the Memory of
Marc Jeannerod
True Friend, Admired Colleague
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This page intentionally left blank
Preface
Let’s cut to the chase.
• Humans have language; other creatures do not.
• This is the result of both biological and cultural evolution.
• Humans have language because their brains are different from those of
other creatures.
But, of course, each of these claims needs unpacking.
Don’t bees have language? Haven’t apes been taught sign language? Not
really. Bees have a dance that lets them tell other bees the location of a source
of pollen they have found. And a bonobo (a species of ape also called a pygmy
chimpanzee) has learned to understand spoken English at roughly the level
of a 2-year-old child. But when it comes to the ability to put a large number of
symbols together in new and complex combinations (like this sentence) and
have others understand what is meant (hopefully also true of this sentence),
nonhumans are out of the running. Human language is not just speech but
includes the gestures that accompany speech, and the sign languages of the
deaf as well. It both builds upon and differs immensely from the communi-
cation systems of our primate cousins. So one aim of this book is to discuss
how monkeys and apes communicate using vocalizations, hand gestures, and
facial expressions, whether in the wild or raised by humans. This will let us
develop the notion of protolanguages, forms of communication used by our
distant ancestors that were richer and more open than those now used by non-
human primates but lacked the astounding subtlety and fl exibility of human
languages as we know them today.
What about evolution? Some people deny it, claiming that each species was
created in its present form and will ever remain so. Yet the key idea behind
Darwin’s theory of evolution is simply that organisms vary, and that some of
the resulting variants reproduce more successfully than others. Let bacteria
loose in a hospital, and random variation will mean that some are more resis-
tant to antibiotics than others—and it is hardly surprising that those bac-
teria with the greater resistance to antibiotics reproduce more successfully
while other strains tend to die out, so that over time the population changes
vii
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viii Preface
completely from its original form. It was Darwin’s genius to understand that
random variation when coupled with selection for success at reproduction
yields creatures that had never appeared before, so that variation and selec-
tion over many many generations can yield species that are completely new.
Evolution does not just “stir the pot,” increasing the population size for some
species and decreasing that of others. Some species go extinct, while new spe-
cies arise.
What I have talked about so far is biological evolution, as the accumulated
changes in the genes passed down from parents to children eventually yield
gene patterns suffi ciently different from those of the ancestors that a new spe-
cies emerges. But I want also to talk about cultural evolution. When I talk of
culture, I do not want to say that there is such a thing as a monolithic French
culture in the sense that all aspects of “French-ness” are determined by a small
causal nexus. Rather, I want to say that a culture has many aspects—the food,
the attitude to education, the interpretation of history, the language, the archi-
tecture, the taboos and ideas of politeness, and on and on—that refl ect the
history of a people. Some of these strongly infl uence each other, while yet oth-
ers seem rather independent. For example, a tradition of excellence in cheese
seems to me unrelated to the language or architecture of France but might
well relate to patterns of gastronomy considered more generally, and these in
turn might interact with traditions of wine making, and thus in turn with
agriculture.
When I speak about cultural evolution, I will be talking about the processes
that shape facets of a human culture in ways that are relatively independent of
human biology. Thus, we might ask how hunter-gatherers became farmers or
how scattered tribes gathered into cities, or how Latin gave rise to the whole
range of Romance languages from Brazilian Portuguese to Romanian. The
key point here is that we cannot hope to understand how the brain changed so
that humans “got” language unless we understand that much of this “getting”
involves historical change—cultural evolution—and not just the evolution of
the biological substrate.
This brings us to brains and brain evolution. If we say a human brain is
different from a frog brain or a rat brain or a monkey brain, what does this
really mean? Are humans smarter than frogs just because their brains are
bigger? Well, whales have much bigger brains than humans, and frogs have
much better eye-tongue coordination. Different brains can be good at different
things and size is only one difference among many. So another task of the book
is to offer some sense of “how brains work” and the way in which a brain has
many different subsystems that compete and cooperate to allow a creature to
conduct a variety of tasks. Here my major focus will be on a comparison of
human brains with those of macaque monkeys. I will look not only at what is
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Preface ix
different about them but also at what is held in common to try to anchor some
ideas about what the brain of our last common ancestor looked like, more than
25 million years ago. This will provide the basis for my later attempts to chart
the changes that must have occurred during human evolution to make us
uniquely equipped for language.
Only the human brain is language ready, in the sense that a normal human
child will learn a language—an open-ended vocabulary integrated with a syn-
tax that supports the hierarchical combination of words into larger structures
which freely express novel meanings as needed—while infants of other species
cannot. Indeed, humans not only can learn an existing language but can take
an active role in the shaping of new languages, as dramatically demonstrated
in the study of emerging sign languages. Syntax refers to the set of “rules”
that tell us how words can be put together to make the sentences of a par-
ticular language, while semantics refers to the meanings of these words and
sentences. But are the rules of syntax innately wired into the human brain? I
will argue that the specifi cs of our capability for language—like our ability to
drive cars or surf the Web—rest only indirectly on the genes, and express the
outcome of cultural developments that exploited prior biological evolution.
This perspective makes it clear that no discussion of the brain will be com-
plete without some sense of its social role in allowing creatures of the same
family or grouping to interact with one another and its adaptive role in allow-
ing a child to learn the fruits of the cultural evolution of its community. A
new dimension in our understanding of how the brain serves social interac-
tion came with the discovery of mirror neurons in the area for hand control
in the brains of macaque monkeys. These are neurons that fi re both when
the monkey is generating a specifi c set of grasps and when it observes simi-
lar grasps performed by others. This led us to ask whether the human brain,
too, contains a mirror system for grasping—a region that would show up as
especially active in brain imaging both when a person performed grasps and
when she observed them. We found such one such area is Broca’s area, a part
of the human brain that had traditionally been associated with the production
of speech. This book presents the Mirror System Hypothesis, namely that the
brain mechanisms that support language evolved on top of the basic mech-
anisms of the mirror system. But grasping is very different from speech. To
understand how one could provide the basis for the other, we will trace the
path whereby the mirror system’s involvement in both grasping and observ-
ing grasping evolved across millions of years to provide the basis for language
parity. This is what makes the shared meaning of language possible, with an
utterance meaning roughly the same for both speaker and hearer.
Language is far more than speech; we use face, voice, and hands when
we talk, and the deaf have sign languages that let them communicate with
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