Ernst Mayr - What Evolution Is: From Theory to Fact

Ernst Mayr was born in Kempten, Germany, in 1904. One

of the main architects of the modern synthesis of genetic

and evolutionary theory, his career has spanned fields as

diverse as ornithology, systematics, zoo-geography, evolu

tionary theory and the philosophy and history of science.

He has written sixteen books, and published more than

seven hundred scientific papers. In 1953 he joined the

Museum of Comparative Zoology at Harvard University,

where he is currently Professor Emeritus.

By Ernst Mayr

T h e Birds of Northern Melanesia (with Jared Diamond)

W h a t Evolution Is

This is Biology

One Long Argument

T h e Principles of Systematic Zoology (with Peter Ashlock)

Toward a New Philosophy of Biology

T h e Growth of Biological Thought

T h e Evolutionary Synthesis (with W. Provine)

Biologie de L'Evolution

Evolution and the Diversity of Life

Populations, Species and Evolution

Animal Species and Evolution

Methods and Principles of Systematic Zoology (with E. G.

Linsley and R. L. Usinger)

Birds of the Philippines (with Jean Delacour)

Birds of the Southwest Pacific

Systematics and the Origin of Species

W H A T E V O L U T I O N I S

Ernst Mayr

PHOENIX

A PHOENIX PAPERBACK

First published in Great Britain in 2002

by Weidenfeld & Nicolson

This paperback edition published in 2002

by Phoenix,

an imprint of Orion Books Ltd,

Orion House, 5 Upper St Martin's Lane,

London W C 2 H 9EA

First published in the USA in 2001

by BasicBooks, a member of the

Perseus Books Group

Copyright Ernst Mayr 2001

T h e right of Ernst Mayr to be identified as the

author of this work has been asserted by him in accordance

with the Copyright, Designs and Patents Act 1988.

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 the copyright owner.

A CIP catalogue record for this book

is available from the British Library.

ISBN 0 75381 368 8

Printed and bound in Great Britain by

Clays Ltd, St Ives pic

C O N T E N T S

Foreword by Jared M. Diamond vii

Preface xiii

Acknowledgments xvii

P A R T I

W H A T I S E V O L U T I O N ?

1 In W h a t Kind of a World Do We Live? 3

2 What Is the Evidence for Evolution on Earth? 13

3 The Rise of the Living World 43

P A R T I I

H O W A R E E V O L U T I O N A R Y C H A N G E A N D

A D A P T E D N E S S E X P L A I N E D ?

4 How and W h y Does Evolution Take Place? 79

5 Variational Evolution 91

6 Natural Selection 127

7 Adaptedness and Natural Selection: Anagenesis 163

P A R T I I I

O R I G I N A N D E V O L U T I O N O F D I V E R S I T Y : C L A D O G E N E S I S

8 The Units of Diversity: Species 177

9 Speciation 192

10 Macroevolution 207

W H A T E V O L U T I O N I S

P A R T I V

H U M A N E V O L U T I O N

11 How Did Mankind Evolve? 257

12 The Frontiers of Evolutionary Biology 293

Appendix A: What Criticisms Have Been Made

of Evolutionary Theory? 297

Appendix B: Short Answers to Frequently Asked Questions

About Evolution 302

Glossary 311

Bibliography 321

Index 331

F O R E W O R D

Evolution is the most profound and powerful idea to have been

conceived in the last two centuries. It was first developed in detail with the 1859 publication of the book On the Origin of Species, by Charles Darwin, who enjoyed a long and incredibly productive

life. While Darwin's professional career began with a round-the

world biological collecting trip on which he embarked at the age of 22 aboard the H M S Beagle, he had already been devoted to outdoor natural history as a boy.

A great deal new has been learned about the workings of evolu

tion since Darwin's day. Wouldn't it be wonderful if Darwin

himself, a clear and forceful writer as well as the greatest biologist of his generation, could write for us a new book on the status of evolutionary thought today! Of course that's impossible, because Darwin died in 1882. This book is the next best: it has been written by a man who is one of the greatest biologists of our own day, who has also enjoyed a long and incredibly productive life, and who is also a clear and forceful writer.

To place Ernst Mayr in perspective, I'll relate an experience of my own. In 1990 I carried out the second bird survey of the

Cyclops Mountains, a steep, high, isolated range rising from the north coast of the tropical island of New Guinea. The survey

proved to be difficult and dangerous, because of the daily risks of falling off the steep slippery trails, of getting lost in the dense jungle, of exposure in cold wet conditions, and of potential conflicts with local people on whom I depended but who had their

own agendas. Fortunately, New Guinea had by then been "pacified" for many years. Local tribes were no longer at war with each other, and European visitors were a familiar sight and were no

longer at risk of being murdered. None of those advantages existed in 1928, when the first bird survey of the Cyclops Mountains was W H A T E V O L U T I O N I S

carried out. I found it hard to imagine how anyone could have survived the difficulties of that first survey of 1928, considering the already-severe difficulties of my second survey in 1990.

That 1928 survey was carried out by the then 2 3-year-old Ernst

Mayr, who had just pulled off the remarkable achievement of com

pleting his Ph.D. thesis in zoology while simultaneously completing his pre-clinical studies at medical school. Like Darwin, Ernst had been passionately devoted to outdoor natural history as a boy, and he had thereby come to the attention of Erwin Stresemann, a famous

ornithologist at Berlin's Zoological Museum. In 1928 Stresemann, together with ornithologists at the American Museum of Natural

History in New York and at Lord Rothschild's Museum near

London, came up with a bold scheme to "clean up" the outstanding remaining ornithological mysteries of New Guinea, by tracking

down all of the perplexing birds of paradise known only from specimens collected by natives and not yet traced to their home grounds by European collectors. Ernst, who had never been outside Europe, was the person selected for this daunting research program.

Ernst's "clean-up" consisted of thorough bird surveys of New Guinea's five most important north coastal mountains, a task

whose difficulties are impossible to conceive today in these days when bird explorers and their field assistants are at least not at acute risk of being ambushed by the natives. Ernst managed to

befriend the local tribes, was officially but incorrectly reported to have been killed by them, survived severe attacks of malaria and dengue and dysentery and other tropical diseases plus a forced

descent down a waterfall and a near-drowning in an overturned

canoe, succeeded in reaching the summits of all five mountains,

and amassed large collections of birds with many new species and subspecies. Despite the thoroughness of his collections, they

proved to contain not a single one of the mysterious "missing"