The Ancient Origins of Consciousness: How the Brain Created Experience

387 Pages·2016·17.72 MB·English

by  Todd E. Feinberg

The Ancient Origins of Consciousness

The Ancient Origins of Consciousness
How the Brain Created Experience
Todd E. Feinberg and Jon M. Mallatt
The MIT Press
Cambridge, Massachusetts
London, England
© 2016 Massachusetts Institute of Technology
Illustrations © Mount Sinai Health System, reprinted with permission (unless other-
wise noted).
All rights reserved. No part of this book may be reproduced in any form by any elec-
tronic or mechanical means (including photocopying, recording, or information stor-
age and retrieval) without permission in writing from the publisher.
This book was set in ITC Stone by Toppan Best-set Premedia Limited. Printed and
bound in the United States of America.
Library of Congress Cataloging-in-Publication Data
Names: Feinberg, Todd E., author. | Mallatt, Jon, author.
Title: The ancient origins of consciousness : how the brain created experience /
Feinberg, Todd E., and Jon M. Mallatt.
Description: Cambridge, MA : The MIT Press, [2015] | Includes bibliographical refer-
ences and index.
Identifiers: LCCN 2015038381 | ISBN 9780262034333 (hardcover : alk. paper)
Subjects: LCSH: Consciousness. | Brain.
Classification: LCC QP411 .F45 2015 | DDC 612.8/233--dc23 LC record available at
http://lccn.loc.gov/2015038381
10 9 8 7 6 5 4 3 2 1
Contents
Preface vii
Acknowledgments xi
List of Figures and Tables xiii
1 The Mystery of Subjectivity 1
2 The General Biological and Special Neurobiological Features of
Conscious Animals 17
3 The Birth of Brains 37
4 The Cambrian Explosion 51
5 Consciousness Gets a Head Start: Vertebrate Brains, Vision, and the
Cambrian Birth of the Mental Image 69
6 Two-Step Evolution of Sensory Consciousness in Vertebrates 101
7 Searching for Sentience: Feelings 129
8 Finding Sentience 149
9 Does Consciousness Need a Backbone? 171
10 Neurobiological Naturalism: A Consilience 195
Appendix: Table References 229
Notes 251
References 287
Index 349

Preface
How is consciousness created? When did it first appear on Earth? How did it
evolve and which living animals have it? Consciousness researcher Todd Fein-
berg has been pondering these questions for over twenty years, while biolo-
gist Jon Mallatt has been fascinated by the early evolution of animals for an
even longer time, so in 2013 we teamed up to see if we could find some
answers. Today, consciousness studies are undergoing a great surge of interest,
as long-standing philosophical questions are starting to be addressed scientifi-
cally. In this book we draw upon the diverse fields of neuroscience, evolution-
ary neurobiology, and philosophy to answer these questions. We focus on
primary or sensory consciousness, which is the most basic type and means just
having any kind of experience at all. Using as a starting point philosopher
Thomas Nagel’s proposal that conscious animals have experiences that con-
stitute “something it is like to be,” we seek the evolutionary origins of central
philosophical indices of consciousness such as John Searle’s “ontological subjec-
tivity” and David Chalmers’s “hard problem of consciousness” (how the
physical brain produces personal experience). By applying a range of recent
discoveries about the nervous systems of many different kinds of animals,
about animal behavior, and about evolution and ancient life on Earth, we aim
to identify the date when sensory consciousness and animal sentience first
appeared and the “hard problem” was created.
This book is written for a wide range of readers: those interested in big
philosophical questions about life and meaning, in consciousness and brain
science, the vertebrate and invertebrate animals, or fossils and deep time.
These fields are vast and varied, but we strive to cover and join them all, pre-
senting at least their basics without demanding that the reader has an expert
background in any of them. Still, we did not skimp as we worked to present
clearly such topics as the full anatomy of vertebrate brains, the defining phil-
osophical axioms of conscious states as well as the brain structures associated
viii Preface
with consciousness, the theories and controversies of consciousness research,
the first explosive diversification of animals half a billion years ago, the role
of the senses in survival, neural pathways, the various kinds of vertebrates
and their evolutionary histories, learning in animal behavior, the origins of
pleasure and pain, and even some invertebrate biology.
In the first part of this book, we explain the basic philosophical puzzles of
consciousness and then begin to assemble a list of features that seem respon-
sible for consciousness: the “correlates” of consciousness. With this list,
we start to formalize our own scientific theory of consciousness called
neurobiological naturalism, previously proposed by Feinberg, systematically
laying it out here so that it can be adjusted by the discoveries of the
later chapters.
Next, we consider the fossil record of animal evolution, as well as the liv-
ing groups of animals that descended from the ancient ancestors. We exam-
ine the great “Cambrian explosion” of animal diversity, which occurred
between about 560 and 520 million years ago, and produced all the known
animal phyla (vertebrates in the chordate phylum, arthropods, molluscs,
etc.). Most importantly, this explosion also produced the first complex ner-
vous systems and brains, the first complex behaviors in animals, and the
earliest evidence of animal cognition. We deduce that in the first verte-
brates, our fishlike early relatives, something wonderful occurred. That is,
these neural advances were accompanied by the first appearance of con-
sciousness, when simple reflexives evolved into a unified “inner world” of
experiences filled with the most mysterious feature of consciousness, called
“qualia” or the subjective feeling of things. The first qualia we consider are
mapped m ental images of the external world as sensed by vision, hearing,
smell, and the other “distance senses.” We refer to this as m apped exterocep-
tive consciousness. Challenging conventional wisdom and long-standing
taboos, we then deduce that all vertebrates are conscious, not just humans
and other mammals but also every fish, amphibian, reptile, and bird. All
vertebrates have always been conscious, but we detect a large, memory-
enhanced advance in sensory consciousness in the first mammals and first
birds, when the end-site of consciousness switched from the lower midbrain
(tectum) to the higher cerebrum.
While the book’s first half is about exteroceptive consciousness of the dis-
tance senses—experiences that can exist without any emotion—we next cover
another fundamental aspect of consciousness called s entience that includes
affect and entails positive and negative feelings. By surveying which animals
Preface ix
living today show the behaviors and brain structures known to be associated
with affective feelings, we deduce that all vertebrates past and present have
affective consciousness, as well as mapped exteroceptive consciousness.
Then, having worked out the markers that identify both aspects of con-
sciousness in the vertebrates, we apply these same criteria to the invertebrates,
and find that the arthropods (including insects and crabs) and cephalopods
(like the octopus) meet many of the criteria for exteroceptive and affective
consciousness. This would mean that consciousness evolved simultaneously
but independently in the first arthropods and first vertebrates over half a bil-
lion years ago.
The final chapter summarizes our findings about which animals are con-
scious, what brain regions are involved in its creation, and how consciousness
first evolved. Consciousness in fact turns out to be a more diverse and wide-
spread evolutionary adaptation than most workers in the field have realized.
Our analysis leads us to update our theory of neurobiological naturalism. This
updated version, still based fully on known biological laws and principles, is
then used to tackle the most fundamental philosophical question of the
nature of consciousness: how does the material brain create subjective experi-
ence? We find an answer in the transitions from reflex-to-image and from
reflex-to-affect, as they occurred over 520 million years ago.
We gain even more insight by subdividing the problem, that is, by tracing
the origins of four different aspects of consciousness: not only qualia (1), but
(2) unity, or why the conscious experience is unified; (3) referral, or why con-
scious brains focus experience on the outer world and inner body, but never
ever experience the workings of their brain neurons; and (4) m ental causation ,
or how immaterial consciousness can cause changes in the material world.
Overall, our analysis of the neural origins of sensory consciousness
attempts to cut through the Gordian knot of the mind–brain problem and
provide a path of reconciliation between a philosophy of personal subjectiv-
ity and the objective structure and functions of the brain. It does so by chron-
icling the evolution of the first “conscious brains,” while also incorporating
the neurobiological and p hilosophical aspects of consciousness.
The book’s special contribution is its finding that consciousness can be
understood if we combine the evolutionary, neurobiological, and philosoph-
ical approaches. In fact, combining the three approaches is essential to solv-
ing the problem. Each approach has limitations that cannot be recognized
unless someone considers the full picture from all three points of view. For
example, the biological approach works to solve problems by reducing them