Evolution Above the Species Level 9780231881869

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EVOLUTION ABOVE THE SPECIES LEVEL

N U M B E R X I X OF T H E

COLUMBIA BIOLOGICAL E D I T E D AT C O L U M B I A

SERIES

UNIVERSITY

E V O L U T I O N ABOVE THE SPECIES LEVEL Bernhard Rensch Professor of Zoology in the University of Münster

NEW YORK:

MORNINGSIDE

COLUMBIA UNIVERSITY

HEIGHTS PRESS

First published in this edition 1959 by Methuen ir Co. Ltd., London Originally published in 1954 by Ferdinand Enke Verlag, Stuttgart as Neuere Probleme der Abstammungslehre 2nd edition English translation © 1959 Columbia University Press Second printing 1970 ISBN 0-231-02296-4 Library of Congress Catalog Number: 58-13505 Printed in the United States of America

Foreword It is very fitting to have the English translation of Rensch's Evolution Above the Species Level published in 1959, the centenary year of Darwin's classic On the Origin of Species. The work of Professor Rensch is one of the great books which have appeared since 1940 and which may fairly be said to have given shape to the modern biological, or synthetic, theory of evolution. The biological theory is the heir to and direct descendant of Darwin's seminal discovery. The intellectual continuity between them is evident and unbroken, but this does not diminish the importance of the radical changes which the century and particularly the last two decades of biological research, thought, and discussion have brought. Apart from the discovery of a great mass of facts, some of them of cardinal importance, there has been a remarkable movement towards synthesis of previously very nearly disconnected lines of investigation and speculation. Instead of the scarcely related 'theories' put forward by systematists, geneticists, paleontologists, and others, we have now a theory of evolution which embraces biology. Together with an attempt by Huxley (1942) which fell rather short of synthesis, we have had the works of Mayr (1942) stemming from zoological and of Stebbins (1950) stemming from botanical systematics and genetics, of Simpson (1944, further developed in 1953) from paleontology, of Schmalhausen (1946 in Russian, 1949 in English) from comparative morphology, of Darlington (1939) and White (1945, 1954) from cytology and genetics, and of Rensch (the two German editions in 1947 and 1954) from systematics, comparative morphology, and paleontology. Notwithstanding their having been based primarily on different bodies of evidence, all these works came to substantially identical conclusions. It is, indeed, a grand synthesis. This should not be taken to mean that the theory of evolution is now complete except for some emendation. On the contrary, radical changes and major upsets are not only possible but almost certain to occur. The progression of science is, however, uneven; periods of broadening of the evidential base alternate with tides of generalization and forward leaps of understanding. It is our privilege to live in a period of the latter kind, in which the book of Rensch marks one of the forward leaps. Columbia University in the City of New York 1 January, 1959

THEODOSIUS

v

DOBZHANSKY

Preface The greater part of this book was written in the last years of the war. My intention was not to present a compilation of known facts brought to light by evolutionary research, but rather to outline the major rules governing the processes of evolution. I wanted to attempt a causal explanation, partly based on new material, with the intention of proving that very probably the major trends of evolution are brought about by the same factors that bring about race and species formation. The first German edition, which came out in 1947, could refer to the works by J. S. Huxley (1942), Simpson (1944), and Mayr (1942), published in England and the United States during the war, only in an addendum after final proof-reading was completed. It was not until the second edition (Stuttgart, 1954) was prepared that the material in these books, as well as in those by Dobzhansky, Haldane, Lack, Edinger, A. H. Miller, and others could be incorporated. The authors were so kind as to place their books at my disposal. I was surprised to find that many scientists, though working independently and using quite different materials as the bases of their studies, had arrived at the same conclusions. For the first time in this century there was a rather general agreement among paleontologists, geneticists, systematists, and comparative anatomists. The present English translation is based upon the second German edition, and only a few alterations and additions have been made. These consist chiefly of the abridgement of material that is of minor importance and the inclusion of quotations from recent literature. It has not been possible, however, to deal with all the numerous special evolutionary studies available in the most recent literature, as this would have increased too greatly the size of the book. The rules governing transspecific alterations of the structural type (Chapters 4 and 6) which - in part - have been newly established are treated in more detail, because they represent a sound means of appreciating organic evolution as a whole and because they exemplify the regularities of the major lines of evolution. The chapter on the evolution of phenomena of consciousness has been reworded so as to be intelligible to those readers who are not too well acquainted with philosophical and epistemological considerations. In spite of its somewhat hypothetical character, I have not omitted this chapter because the majority of the readers of the German edition - insofar as their written and spoken comments have reached me - considered it essential and stimulating. vii

E V O L U T I O N ABOVE THE SPECIES LEVEL

It is my pleasant duty to express my cordial gratitude to Professor Theodosius Dobzhansky for suggesting this translation of my book and for going through the manuscript. Thanks are also due to the Manager of the Publication Department of Columbia University Press, Mr Henry H. Wiggins, for his obliging cooperation in bringing out the American edition. Finally, I wish to thank Dr Altevogt for translating the German text, which was not too easy in places. B. R E N S C H

Münster, Westphalia March, 1956

viii

Contents

FOREWORD

page

PREFACE

v vii

1. I N T R O D U C T I O N

1

2. T H E C A U S A T I V E F A C T O R S O F I N F R A S P E C I F I C EVOLUTION A. Mutation B. Fluctuations of population size c. Selection D. Isolation E. Hybridization F. Interaction of the evolutionary factors

3 3 9 10 13 14 14

3. T Y P E S O F R A C E A N D S P E C I E S OCCURRING IN NATURE A. Historical races B. Geographic races c. Ecological races D. Sexually isolated races E. Genetic isolation F. Hybrid races G. Review of all types of races

16 16 22 47 50 53 54 55

FORMATION

4. U N D I R E C T E D A N D D I R E C T E D T R A N S S P E C I F I C EVOLUTION A. The problem of phylogenetic trends and orthogenesis B. Nondirectedness of evolution c. Forced development in phylogeny D. Rules of phylogenetic development E. Possible evolution of organisms in extraterrestrial bodies

57 57 59 68 73 76

5. T H E A B S O L U T E S P E E D O F E V O L U T I O N A. The absolute age of various categories B. Factors governing the speed of evolution

82 83 91

ix

EVOLUTION

ABOVE

THE SPECIES

LEVEL

6. T H E R U L E S O F K L A D O G E N E S I S (PHYLOGENETIC BRANCHING) page A. Phases of explosive radiation Historical comments Examples demonstrating 'explosive phases' and periods of explosive radiation Interpretation of the findings B. The phase of specialization i. Gradual loss of evolutionary intensity ii. Irreversibility Transspecific changes of structural systems HI. Rules governing transspecific changes of structural types Constructive genes Allometric growth and its bearing on evolution Physiological consequences of allometric growth Summary of complex differences in species of different body size The gradients of differentiation Phyletic size limits and consequent alterations of the structural type Further correlations. Compensation of body material The problem of somatogenic induction Summary on transspecific alterations of the structural type iv. Parallel evolution Parallel evolution resulting from similarity of hereditary factors Parallelisms in consequence of parallel selection v. Orthogenesis Examples of directed phylogeny and their problems Cope's rule Orthogenetic evolution of organs Reduction of organs c. Overspecialization, degeneration, and extinction I. Excessive growth and 'overspecialization' II. Phylogenetic aging and 'degeneration' HI. Phyletic extinction D. The Effects of phylogenetic alterations in various states of the individual cycle i. Causation and classification of phylogenetic alterations of ontogeny ii. Archallaxis HI. Permanent deviations and heterochronies x

97 98 98 99 103 112 112 123 126 126 129 133 160 165 169 170 179 187 190 191 192 198 203 203 206 218 222 226 226 232 234 239 239 241 246

CONTENTS

iv. Deviations confined to early and intermediate states of ontogeny (coenogeneses) page v. Alterations by additional phases of development (anabolies) vi. Palingenesis, proterogenesis, and neoteny vii. Alternation of generations viii. Frequency of the different types of ontogenetic alterations and their bearing on evolution E. Evolution of new structural types and new organs i. The origin of new structural types ii. The origin of new organs HI. Summary 7. A N A G E N E S I S ( P R O G R E S S I V E E V O L U T I O N ) A. Historical comments B. Facts of anagenesis c. Analysis of anagenesis i. Increase of complexity ii. Increased rationalization HI. Special complexity and rationalization of nervous systems iv. Increased plasticity of structures and functions v. Improvement permitting further improvement vi. Increased independence of the environment and increased autonomy VII. Regressions VIII. S u m m a r y

A. B. c. D.

263 266 266 274 279 281 281 284 289 289 291 292 295 297 298 298 301

OF LIFE

309

The problem of spontaneous generation Characteristics of life Series of organisms with successive reduction of vital characters The evolution of neucleoproteins

9. A U T O G E N E S I S , E C T O G E N E S I S , A N D GENESIS 10. E V O L U T I O N NESS

253 258 262

299

D. Remarks on human descent 8. T H E E V O L U T I O N

250

OF P H E N O M E N A

OF

309 310 311 315

BIONOMO317

CONSCIOUS322

A. Introduction B. General review of the phenomena of consciousness c. General phylogeny of the phenomena of consciousness xi

322 323 327

E V O L U T I O N ABOVE THE SPECIES LEVEL

D. Phylogeny of the special phenomena i. Phylogeny of sensations ii. Phylogeny of conceptions HI. Judgments, conclusions, and actions of insight E. Philosophy and the evolution of psychic phenomena F. Psychic processes and somatic evolution 11. C O N C L U S I O N

page 335 335 339 344 349 356 358

POSTSCRIPT

361

BIBLIOGRAPHY

363

AUTHOR INDEX

404

GENERAL INDEX

412

xii

Figures 1. Spreading of the melanic mutant (carbonaria) of the moth Amphidasis betularia page 21 2. New Zealand flycatcher and melanic mutant; New Guinea hawk and white mutant 22 3. Distribution of Parus major 'Rassenkreis' 29 4. Range of races in the Trichoglossus ornatus 'Rassenkreis' 31 5. Geographic races of the lizard Ablepharus boutonii 35 6. Three extreme races of Lacerta pityusensis from the Pityusic Islands 37 7. Species of land snail from a small island 38 8. Arboreal snail Papuina wiegmanni and variants 39 9. Range of Papuina wiegmanni in New Britain 39 10. Average length of wings in populations of serins (