Evolving Brains (scientific American Library)

EVOLVING BRAINS Evolving Brains John Morgan Allman SCIENTIFIC AMERICAN LIBRARY A division of HPHLP New York Cover and text design: Victoria Tomaselli Illustration: Joyce Powzyk and Fine Line Studio Library of Congress Cataloging-in-Publication Allman, John Morgan. Evolving brains / John Morgan Allman. p. cm. - (Scientific American Library, 1040-3213; no. 68) Includes bibliographical references and index. ISBN 0-7167-5076-7 1, Brain-Evolution. I. Title. II. Series: Scientific American Library series; no. 68 QP376.A423 1999 573.8'6-dc21 98-37576 CIP ISSN 1040-3213 © J 999 by Scientific American Library. All rights reserved. No part of this book may be reproduced by any mechanical, photographic, or electronic process, or in the fonn of a phonographic recording, nor may it be stored in a retrieval system, transmitted, or otherwise copied for public or private use, without written pen11ission from the publisher. Printed in the United States of America Scientific American Library A division of HPHLP New York Distributed by W. H. Freeman and Company 41 Madison Avenue, New York, NY 10010 Houndmills, Basingstoke RG21 6XS, England First printing, December 1998 This book is number 68 of a series. To my father, who encouraged me to ask questions Preface IX OJ Brain Basics w Comparing Brains OJ Duplicated Genes and Developing Brains []] Eyes, Noses, and Brains 63 - []] Warm-Blooded Brains 85 w Primate Brains []] The Evolution of Big Brains Readings 1 15 121 209 Sources of Illustrations Index 159 219 215 43 n a crisp October evening in 1966, I decided to study brain evolution. I wanted to discover the underlying physiological mechanisms responsible for brain evolution by comparing living animals. I knew that primates excelled in their use of vision, and I thought a particularly useful approach would be to trace how the visual image on the retina was transformed into neural signals in the brains of primates. I was a graduate student in anthropology, and I knew that I would have to become proficient in neurophysiology to undertake this investigation. Clark Howell, my adviser at the University of Chicago, enthusiastically supported my rather unconventional goal and suggested that I conduct my research at the Laboratory of Neurophysiology at the University of Wisconsin while still a graduate student at Chicago. Anthropologists typically go off to some exotic locality to conduct their thesis research, so my trip was shorter than most. I was doubly fortunate that Clinton Woolsey and Wally Welker welcomed me to the Laboratory. At Wisconsin I began a fruitful collaboration with Jon Kaas that led to our early mapping studies of the visual cortex in owl monkeys. Our studies were based on the pioneering microelectrode mapping techniques developed by Wally and Vicente Montero. Jon and I uncovered a far larger and more complex set