Ian Tattersall - The Fossil Trail: How We Know What We Think We Know About Human Evolution (First Edition)

Page ii

Page v

The Fossil Trail

How We Know What We Think We Know about Human Evolution

Ian Tattersall

American Museum of Natural History

OXFORD UNIVERSITY PRESS

New York Oxford

Page vi

Oxford University Press

Oxford New York Athens Auckland Bangkok Bombay Calcutta Cape Town Dar es Salaam Delhi Florence Hong Kong Istanbul Karachi Kuala Lumpur Madras Madrid Melbourne Mexico City Nairobi Paris Singapore Taipei Tokyo Toronto

and associated companies in Berlin Ibadan

Copyright 1995 by Oxford University Press, Inc.

First published by Oxford University Press, Inc., 1995

First issued as an Oxford University Press paperback, 1996

Oxford is a registered trademark of Oxford University Press

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of Oxford University Press.

Library of Congress CataloginginPublication Data

Tattersall, Ian.

The fossil trail: how we know what we think we know about human

evolution / Ian Tattersall.

p. cm.

Includes bibliographical references and index.

ISBN 0195061012

ISBN 0195109813 (Pbk.)

1. Human evolution. 2. Fossil man. 3. Anthropology, Prehistoric.

I. Title.

GN281.T357 1995

573.2dc20 9431633

10 9 8 7 6 5 4 3 2 1

Printed in the United States of America on acidfree paper

Page vii

Sir Isaac Newton once said that if he had seen farther, it was because he had stood on the shoulders of giants. In these uncharacteristically gracious words he acknowledged a debt to the past that is universal among scientistsas well as (presumably unintentionally) a burden that is equally universal. For although every scientist starts from a base established by his (or her) predecessors, what you see from your lofty elevation depends on how tall your giant is, and in what direction he happens to be facing. That's what this book is about, for how you read your evidence is at least partly conditioned by what you are expecting to find and in the science of paleoanthropology preconception may well have played an even larger role than in most other sciences. Of course, the study of human evolution has come a long way since its early days, in terms both of the basic fossil evidence and of how it is analyzed. But we are still largely in thrall to received wisdom, and this brings us back to the central theme of this book. Howand whyhave we come to know what we think we know about human evolution: about the complex history of our own biological past?

Most popular books about human evolution in recent years have been based on the experience of individual paleoanthropologists in the field, and thus have at least implicitly projected the notion that reconstructing the past is essentially a matter of discovery: find enough fossils, and all will be revealed. This in turn reflects the idea that paleontology is somehow like a giant jigsaw puzzle, and that once we have all the pieces they will fit together to disclose the full picture or at the very least, that when we have enough pieces we will be able to discern the broad outlines of the design.

Hence the traditional paleontologists' lament: the inadequacy, almost invariably described as "woeful," of the fossil record. Well, it's true that we will never have a

"complete" fossil record. In fact, we will never have a human fossil record that preserves even one thousandth of one percent of all the individuals that have ever lived.

But even now we have a reasonably good sampling of fossil specieseven fossil human speciesthat should allow us, by appropriate analysis, to gain a provisional idea of the major events that led to the emergence of our own kind on Earth. I use the term Page viii

"provisional" in a positive sense, because all scientific knowledge is provisional indeed, how can we expect to make progress in any area of science if what we believe now is not somehow inaccurate or at least incomplete? A scientific idea is one that can be tested in the light of new observations, whether these new observations are experimental or are based on new discoveries or on new analyses of old discoveries. Popular misconceptions to the contrary, scientific ideas are not immutable declarations of truth, nor are they intended to be.

But the starting point for any new set of hypotheses is the set of hypotheses that preceded it and what we believe today can never be fully independent of what we believed yesterday. Moreover, in anything as close to our own ego as the story of our own origins, what we think we know cannot be independent of what we believe about ourselves. Clearly, it is too much to ask that scientific opinions in this emotive realm should be entirely independent of prevailing social thought and attitudes. So in trying to comprehend how we know what we think we know today about our evolution, it's important to look back at the past of paleoanthropology and to understand by what circuitous routes we have arrived at that knowledge. What we have believed in the past, the evidence we have now, and how we look at that evidence all interact in a complex way. And that is why this book follows a historical path.

I.T.

NEW YORK

Page ix

Acknowledgments

No book like this one could have been written without the help and influence of very many individuals. They are too many to be named individually, although most are identified in the text. Thank you all.

My American Museum of Natural History colleagues Niles Eldredge, Eric Delson, and Richard Milner have been kind enough to read the manuscript and to offer valuable suggestions. None of themleast of all Ericwill have agreed with all that is said here, but each deserves my gratitude.

Paleoanthropology is above everything a visual science, and good illustration is critical. I have been fortunate indeed to work in the preparation of this volume with Don McGranaghan and Diana Salles. The work of each is identified by initial at the end of the individual figure captions, and my deepest appreciation goes to both, as it does to Jaymie Brauer, who cheerfully chased down the most obscure of references and (less cheerfully) prepared the index.

This volume would never have been begun without the vision and prompting of Bill Curtis, now of WileyLiss Publishing. And it would most certainly never have been finished without the persistence, patience, and encouragement of Kirk Jensen, of Oxford University Press. To both I am most grateful, as I am to Carole Schwager for her careful copyediting and to Dolores Oetting for seeing the book through production.

Finally, my appreciation goes once again to the American Museum of Natural History, both for affording me the opportunity to write, and for the incomparable ambience in which I have been able to do it.

Page x

Contents

Abbreviations xi

1 Before Darwin 3

2 Darwin and After 17

3 Pithecanthropus 31

4 The Early Twentieth Century 41

5 Out of Africa... 53

6... Always Something New 69

7 The Synthesis 89

8 Olduvai Gorge 105

9 Rama's Ape Meets the Mighty Molecule 119

10 Omo and Turkana 127

11 Hadar, Lucy, and Laetoli 141

12 Theory Intrudes 159

13 Eurasia and Africa: Odds and Ends 171

14 Turkana and OlduvaiAgain 187