Character Concept in Evolutionary Biology (eBook)

Gunter P. Wagner (Herausgeber)

eBook Download: PDF | EPUB

2000 | 1. Auflage
622 Seiten
Elsevier Science (Verlag)
978-0-08-052890-8 (ISBN)

Infos

Almost all evolutionary biologists, indeed all biologists, use particular features to study life. These characteristics or features used by evolutionary biologists are used in a particular way to unravel a tangled evolutionary history, document the rate of evolutionary change, or as evidence of biodiversity. Characters are the data of evolutionary biology and they can be employed differently in research providing both opportunities and limitations. The Character Concept in Evolutionary Biology is about characters, their use, how different sorts of characters are limited, and what are appropriate methods for character analysis. Leading evolutionary biologists from around the world are contributors to this authoritative review of the character concept. Because characters and the conception of characters are central to all studies of evolution, and because evolution is the central organizing principle of biology, this book will appeal to a wide cross-section of biologists.

Key Features
* Focuses upon characters -- fundamental data for evolutionary biology
* Covers the myriad ways in which characters are defined, described, and distinguished
* Includes historical, morphological, molecular, behavioral, and philosophical perspectives

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Almost all evolutionary biologists, indeed all biologists, use particular features to study life. These characteristics or features used by evolutionary biologists are used in a particular way to unravel a tangled evolutionary history, document the rate of evolutionary change, or as evidence of biodiversity. "e;Characters"e; are the "e;data"e; of evolutionary biology and they can be employed differently in research providing both opportunities and limitations. The Character Concept in Evolutionary Biology is about characters, their use, how different sorts of characters are limited, and what are appropriate methods for character analysis. Leading evolutionary biologists from around the world are contributors to this authoritative review of the "e;character concept."e; Because characters and the conception of characters are central to all studies of evolution, and because evolution is the central organizing principle of biology, this book will appeal to a wide cross-section of biologists. Focuses upon "e;characters"e; -- fundamental data for evolutionary biology Covers the myriad ways in which characters are defined, described, and distinguished Includes historical, morphological, molecular, behavioral, and philosophical perspectives

Inhalt

Front Cover 1
THE CHARACTER CONCEPT IN EVOLUTIONARY BIOLOGY 4
Copyright Page 5
CONTENTS 8
CONTRIBUTORS 12
PREFACE 16
Foreword 18
Characters, Units and Natural Kinds: An Introduction 26
SECTION I: HISTORICAL ROOTS OF THE CHARACTER CONCEPT 36
Chapter 1. A History of Character Concepts in Evolutionary Biology 38
Chapter 2. An Episode in the History of the Biological Character Concept: The Work of Oskar and Cécile Vogt 62
Chapter 3. Preformationist and Epigenetic Biases in the History of the Morphological Character Concept 82
SECTION II: NEW APPROACHES TO THE CHARACTER CONCEPT 102
Chapter 4. Character Replication 106
Chapter 5. Characters as the Units of Evolutionary Change 134
Chapter 6. Character Identification: The Role of the Organism 166
Chapter 7. Functional Units and Their Evolution 190
Chapter 8. The Character Concept: Adaptationalism to Molecular Developments 224
Chapter 9. The Mathematical Structure of Characters and Modularity 240
Chapter 10. Wholes and Parts in General Systems Methodology 262
SECTION III: OPERATIONALIZING THE DETECTION OF CHARACTERS 282
Chapter 11. What Is a Part? 284
Chapter 12. Behavioral Characters and Historical Properties of Motor Patterns 310
Chapter 13. Homology and DNA Sequence Data 328
Chapter 14. Character Polarity and the Rooting of Cladograms 344
SECTION IV: THE MECHANISTIC ARCHITECTURE OF CHARACTERS 364
Chapter 15. The Structure of a Character and the Evolution of Patterns 368
Chapter 16. Characters and Environments 388
Chapter 17. The Genetic Architecture of Quantitative Traits 414
Chapter 18. The Genetic Architecture of Pleiotropic Relations and Differential Epistasis 436
Chapter 19. Homologies of Process and Modular Elements of Embryonic Construction 460
Chapter 20. Comparative Limb Development as a Tool for Understanding the Evolutionary Diversification of Limbs in Arthropods: Challenging the Modularity Paradigm 480
SECTION V: THE EVOLUTIONARY ORIGIN OF CHARACTERS 514
Chapter 21. Origins of Flower Morphology 518
Chapter 22. Origin of Butterfly Wing Patterns 536
Chapter 23. Perspectives on the Evolutionary Origin of Tetrapod Limbs 556
Chapter 24. Epigenetic Mechanisms of Character Origination 584
Chapter 25. Key Innovations and Radiations 606
INDEX 632

Textauszug

Foreword

R.C. Lewontin

“Like following life through creatures you dissect, you lose it in the moment you detect.” Already in the 18th century, Alexander Pope had expressed the fundamental problem in the study of living beings, a problem that continues to plague us. How are we to apply an analytic method to living objects in such a way that the phenomenon we wish to understand is not destroyed in the very process of analysis? What are the “natural” suture lines along which we can dissect the organism to understand properly its history and function? For Pope to dissect a creature meant only to cut it up with a knife, but for the modem biologist, and especially the evolutionist, the problem is conceptual. It seems that we cannot carry on our business without using characters, yet there is nothing more dangerous to the proper understanding of biological processes than that first act of characterization. How are we to recognize the “true” characters of organisms rather than imposing upon them arbitrary divisions that obscure the very processes that we seek to understand? That is the question of this book. No issue is of greater importance in the study of biology.

Modem biology is a battleground between two extreme ontological and epis- temological claims about living creatures, claims that reflect the history of biological study. One takes as its model the physical sciences and their immense success in manipulating and predicting the behavior of much of the inanimate world. In that domain there are a few basic laws governing all phenomena, the laws of Newton and Einstein, of thermodynamics, of electromagnetic theory, and of nuclear forces. The objects of study either are universal elementary bits and pieces, particles, atoms, and molecules or are composed of those bits and pieces in an unproblematical way. They are Cartesian machines, clocks that can be understood by looking at the articulation of the gears and levers that are clearly recognizable as their parts. It is the extreme reductionist model that validates the various genome-sequencing projects. When we possess the complete description of the DNA sequence of an organism, we have all the information we need to understand the organism. This extreme molecular reductionism is the outgrowth of the 19th-century program to mechanize biology, to expunge the vestiges of mysticism from the study of life, and to bring that study within the domain of universal physical law. Darwinism, Mendelism, biochemistry and biochemical physiology, and Entwicklungsmechanik were its intellectual precursors.

At the other extreme is a radical holism that denies the possibility of learning the truth through analysis. The living world is a seamless whole and any perturbation of one bit of the living world may be propagated in unpredictable ways throughout the biosphere and certainly throughout the entire physiology of any individual organism. It is the whole as whole that must be studied. The belief in this holism has been greatly fortified by the discovery of chaotic regimes in fairly simple dynamical processes, showing that even minor perturbations may give rise to apparently unpredictable dynamical histories. In an attempt to make holism a science there is a movement to develop a mathematical theory of “complex” systems in the hope that complexity will have its own, irreducible laws. Modem “scientific” holism is a return to the obscurantist holism that informed biology before the middle of the mid-19th century and the romantic organicism and naturalism that opposed the development of mechanistic biology, tainted by the stench of the “dark Satanic mills.”

Both extreme reductionism and holism escape the character problem. For the reductionist the characters are obvious and unproblematical. They are molecules and distinct sequences of molecular interactions. There is a signaling pathway, composed of controlling regions of DNA in certain genes and proteins coded by other genes, that determines the differentiation of a particular part of an embryo. The part is unproblematical because it is the outcome of the operation of a distinct and well-defined autonomous collection of genetic elements. If genes determine organisms, then parts of organisms are defined by the autonomous assemblages of genes that cause them. One of the ironies of the perverse history of scientific language is that, in its original sense, this reductionism is a truly organic view. The use of the word “organism” for a living being and the “organic” view of life were originally metaphors likening the body to the musical organ, a system of well-defined articulated parts that contribute to the operation of a whole. Nothing is more transparently clock-like and easy to break down into separate functional parts than a musical organ. The keyboard, the foot pedals, the bellows, each set of pipes are all clearly separate organs (in the biological sense) with easily defined relations among them. Indeed, except for the source of air all the parts can be individually disabled without interfering with the operation of others. If the vox humana stop is inoperative, nothing prevents the organist from playng the entire program with the flauto, and if the keyboard is not working, the foot pedals will still serve to play the tune. If bodies were really organic, the problem of characters would not exist and biology would be a simple science. Radical holism, on the other hand, finesses the problem of characters by denying their real causal existence, making of them merely mental constructs. Their text is Wordsworth:

Our meddling intellect

Mis-shapes the beauteous forms of things:—

We murder to dissect.

Because everything is connected to everything else, the delineation of characters is necessarily arbitrary and ultimately destructive of the truth. Moreover, it leads us to a dangerous hubris about how we safely intervene in the world.

The problem for biology is that neither a radical holism nor an organic reductionism captures the actual structure of causation in the living world. It is clearly not the case that everything is connected effectively to everything, even in the relatively simple world of physical objects. Gravitational forces are everywhere, but because gravitational force is weak and falls off with the square of distance, the entire universe of objects is not locked up in an effective gravitational whole. I can feel quite confident that the motion of my body exerts no effective gravitational pull on the person who passes me in the street. It cannot be that the alteration of every part of the body of an organism has a palpable functional or developmental effect on every other part or else evolution could never have occurred. Selection on every bit of the organism would result in simultaneous pressure on every other bit, requiring the organism to be totally rebuilt in response to every selective change. Nor can every species community be totally overturned if one or another species drops out of the mix, although large perturbations may sometimes happen. Despite the popular wisdom, the death of a single butterfly in Madagascar will not have effects propagated throughout the living world or else the temporal instability of the biosphere would have long since resulted in the extinction of all life.

It is necessarily the case that the material world is subdivided into relatively small sets of objects and forces within which there are effective interactions and between which there is operational independence, what has come to be called “quasi-independence.” This fact immediately predisposes us to both a conceptual and a methodological reductionism. Let us break down organisms into the smallest pieces we can and then slowly put them back together again, a bit at a time, to see which parts are, in fact, in effective interaction with each other. We can then map out the quasi-independent subsets, the natural characters that constitute living systems. No one can deny that this methodological reductionism has had great success. Everything we know about biochemistry and physiology, about basic cellular mechanisms of replication, about development, has been learned by taking things into pieces and putting them back together again. That is how we know that the differentiation of digits from a limb bud is independent of the differentiation of the external pinna of the ear or that the metabolism of alcohol as affected by the enzyme coded by the alcohol dehydrogenase gene is physiologically separable from the formation of eye pigment in Drosophila. That digits and ear pinna or alcohol and eye pigment biochemistry are different characters in the developmental or physiological sense need not have been the case. It simply turned out that way and we would not have been forced to reorganize our understanding of biology had things turned out differently. Methodogical reductionism seems to work, so why not pursue it as a program and let nature speak to us, delineating characters for us bit by bit? We do not do this because it is the failures of a method, not its successes, that are its test.

Organisms occupy a special part of the property space of physical objects. First, they are intermediate in size between plants and particles. Second, they are internally functionally heterogeneous, being composed of many subsystems at many levels. There are different species of molecules in the cell, spatially localized in organelles and cellular regions, and, in multicellular organisms, different cells in each organ and different organs with different functions. Third, many of the molecules and organelles in cells are present in...

Produkt-Details

• Erscheint lt. Verlag: 31.10.2000
• Sprache: englisch
• Themenwelt: Naturwissenschaften ► Biologie ► Evolution
• Themenwelt: Naturwissenschaften ► Biologie ► Ökologie / Naturschutz
• Themenwelt: Technik
• ISBN-10: 0-08-052890-2 / 0080528902
• ISBN-13: 978-0-08-052890-8 / 9780080528908