In 1936, I had to find a subject for the presidential address to the Zoology Section of the British Association. After some hesitation, I chose “Natural Selection and Evolutionary Progress”, since it seemed to me that these were two interrelated topics of fundamental biological importance, yet on which much misapprehension existed. Even among professional zoologists the modern conception of natural selection and its mode of operation is quite
different from that of Darwin’s day, but much of the research on which the changed oudook is based is so recent that the new ideas have not spread far. The idea of evolutionary progress, on the other hand, has been undeservedly neglected. Thus it seemed
to me valuable to attempt to give a broad account of the two concepts and their relation to each other.
The result exceeded my expectations. So many of my colleagues expressed interest and the wish that the address might be available in more extended and more permanent form, that
I decided to essay expanding it into a book.
The result is the present volume. I am fully conscious of its limitations and imperfections, but I believe that it will serve a useful purpose. The writing of it has so much clarified my own thinking, and the discussion of the problems that arose with colleagues has resulted in so many ideas and points of view which were novel both to them and to myself, that I am encouraged to believe it will be of general service. I also feel sure that a
classification and analysis of evolutionary trends and processes as observed or deduced in nature, and the attempted relation of them to the findings of genetics and systemadcs, is of first-class importance for any unified biological outlook; and since others better equipped than I seem reluctant to attempt the task, I have tried my hand at it.
Author(s): Huxley, Julian
Edition: 3rd ed.
Publisher: Allen and Unwin
Year: 1974
Language: English
Pages: 705
City: London
Tags: Evolution (Biology);Biological Evolution;Evolution
Preface to the First Edition xi
Introduction to the Third Edition (Seventh Impression) xiii
Chapter i. The Theory of Natural Selection
1. The theory of natural selection 13
2. The nature of variation 17
3. The eclipse of Darwinism 22
Chapter 2. The Multiformity of Evolution
1. The heterogeneity of evolution 29
2. The paleontological data . 31
3. Evolution in rare and abundant species . 32
4. Adaptations and their interpretation 34
5. Adaptation and selection 37
6. The three aspects of biological fact 40
7. The main types of evolutionary process 42
Chapter 3. Mendelism and Evolution
1. Mutation and selection 47
2. Genes and characters. 62
3. The alteration of genic expression 68
4. The evolution of dominance 75
5. Types of mutation . 87
6. Special cases: melanism; polymorphism; fluctuating populations 93
7. Mutation and evolution IIS
Chapter 4. Genetic Systems and Evolution
1. The factors of evolution 12s
2. The early evolution of genetic systems . 131
3. The meiotic system and its adjustment 136
4. The consequences of polyploidy 143
$. Species-hybridization and sex-determination: conclusion 146
Chapter 5. The Species Problem; Geographical Speciation
1. The biological reality of species 151
2. The different modes of spedation; successional species 170
3. Geographical replacement: the nature of subspecies 174
4. Clines (character-gradients) 206
5. Spatial and ecological factors in geographical divergence . 227
6. Range-changes subsequent to geographical differentiation 243
7. The principles of geographical differentiation. 239
Chapter 6. Speciation, Ecological and Genetic
1. Local versus geographical differentiation 263
2. Ecological divergence 265
3. Overlapping spedes-pairs 284
4. Biological differentiation . 295
5. Physiological and reproductive differentiation 308
6. Special cases . 316
7. Divergence with low competition; oceanic faunas 323
8. Genetic divergence 328
9. Convergent spedes-formation 339
10. Reticulate differentiation 351
11. Illustrative examples 3$6
Chapter 7. Spéciation, Evolution, and Taxonomy
1. Different types of spedation and their results . 382
2. Spedes-formation and evolution . . 387
3. Modes of spedation and systematic method 390
Chapter 8. Adaptation and Selection
1. The omnipresence of adaptation . . 412
2. Adaptation and function; types and examples of adaptation 417
3. Regularities of adaptation 430
4. Adaptation as a relative concept 438
5. Preadaptation .... . 449
6. The origin of adaptations: the inadequacy of Lamarckism 457
7. The origin of adaptations: natural selection . . 466
8. Adaptation and selection not necessarily beneficial to the species 478
Chapter 9. Evolutionary Trends
1. Trends in adaptive radiation 486
2. The selective determination of adaptive trends 494
3. The apparent orthogenesis of adaptive trends 497
4. Non-adaptive trends and orthogenes» . 504
5. The restriction of variation 516
6. Consequential evolution: the consequences of differential development 52$
7. Other consequential evolutionary trends 543
Chapter 10. Evolutionary Progress
1. Is evolutionary progress a scientific concept ? 556
2. The definition of evolutionary progress 559
3. The nature and mechanism of evolutionary progress $62
4. The past course of evolutionary progress 369
5. Progress in the evolutionary future 572
Introduction to the Second Edition 579
Bibliography (to the First Edition) 618
Supplementary Bibliography (to the Introduction to the Second Edition) 653
Bibliography to the Introduction to the Third Edition. 661
Index 675
