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Sex and Death

An Introduction to Philosophy of Biology

Science and Its Conceptual Foundations

A series edited by David L. Hull

Kim Sterelny and Paul E. Griffiths

The University of Chicago Press

Chicago and London

Kim Sterelny is currently Reader in Philosophy at the Victoria University of Wellington. He is the author of Language and Reality and The Representational Theory of Mind: An Introduction.

Paul E. Griffiths is currently head of the History and Philosophy of Science unit of the University of Sydney. He is the author of What Emotions Really Are: The Problem of Psychological Categories.

The University of Chicago Press, Chicago 60637

The University of Chicago Press, Ltd., London

© 1999 by The University of Chicago

All rights reserved. Published 1999

08 07 06 05 04 03 02 01 00 99 12 3 4 5

ISBN: 0-226-77303-5 (cloth)

ISBN: 0-226-77304-3 (paper)

Figure 6.3 is from Karen Arms and Pamela S. Camp, Biology, 3d ed. © 1987 by Saunders College Publishing. Reproduced by permission of the publisher. Figure 9.4 is from W. Hennig, Phyhgenetic Systematic, © 1979 by the Board of Trustees of the University of Illinois. Reproduced by permission of the University of Illinois Press.

Library of Congress Cataloging-in-Publication Data

Sterelny, Kim.

Sex and death : an introduction to philosophy of biology / Kim Sterelny and Paul E. Griffiths.

p. cm. — (Science and its conceptual foundations) Includes bibliographical references (p. ) and index. ISBN 0-226-77303-5 (cloth : alk. paper). — ISBN 0-226-77304-3 (pbk. : alk. paper)

1. Biology — Philosophy. I. Griffiths, Paul E. II. Title. III. Series. QH331.S82 1999

570M — dc21 98-47555

CIP

The paper used in this publication meets the minimum requirements of the American National Standard for Information Sciences — Permanence of Paper for Printed Library Materials, ANSI Z39.48-1992.

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Contents

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Preface

This book began long ago and far away, in Chicago in 1993 when one of us (Sterelny) tried out the basic idea on David Hull and Susan Abrams, both of whom were supportive. On Sterelny's return to the Antipodes, he continued to think about the project, and decided that a collaborative project would be more fun to do and would result in a better book. So he talked the idea over with Griffiths and with David Braddon Mitchell, an Australian philosopher of science with interests in both philosophy of biology and Australian botany. Thus the basic body plan of the book was laid down; a body plan that, in contrast to some others, has not remained impervious to developmental and other perturbations. After a couple of years of talking, we seriously got down to writing in 1995. Since 1996 this book has probably been the main project of the two survivors, Braddon Mitchell having been submerged by other plans. He did, however, have a major input into chapter 12.

There are, of course, many different ways to write an introduction to philosophy of biology. One option would be to use biological examples to stalk general issues in philosophy of science — the nature of theory and theory change, causation, explanation, and prediction. There is much to be said for such a book, for philosophy of science, in our view, has been too dominated by exemplars from theoretical physics. That matters: for example, the historical explanations central to, say, geology and evolutionary biology seem importantly different from those of physics. Still, that is definitely not the book we have written. This book is very much focused on the conceptual and theoretical problems generated by the agenda of biology, rather than pursuing a philosophy of science agenda through biological examples.

We have also chosen not to approach philosophy of biology by tracking the conceptual and theoretical development of evolutionary ideas, as David J. Depew and Bruce H. Weber have done in their Darwinism Evolving. There is an occasional nod to the history of the disciplines concerned, but the organizational  {xii}  spinal cord of our book is the conception of evolutionary biology that was developed in the classic works ofMayr, Dobzhansky, Simpson, and Stebbinsin the 1940s. That conception, the “modern synthesis,” dominated evolutionary thinking at least into the late 1960s. The current problems of evolutionary theory have been largely, though not wholly, the result of pressures to rethink that conception. We have chosen to call this core conception “the received view” rather than the “synthesis view” because we represent it in a rather schematic and ideal form. The real synthesis was never wholly uniform, of course, and for the most part the variation within it has not been our concern.

We have called our book Sex and Death: An Introduction to Philosophy of Biology. First, the subtitle: The reader may have noticed that while it speaks of biology, in the preface we have written of evolutionary biology. Indeed, in the text we have focused on evolutionary biology. That focus is not exclusive: chapter 5 explores connections between evolutionary and developmental biology, and chapters 6 and 7 push this exploration further. Those chapters take up the relationship between the role of genes in evolutionary theory and the molecular biology of the gene. Moreover, chapter 11 is devoted to exploring the interplay between evolutionary biology and ecology. But it is true that we have discussed other areas of biology mainly as they relate to evolution. So evolutionary theory and evolutionary theorists loom large over this work. (So we too can say that if we have seen too little, it is because giants have been standing on our shoulders.) This emphasis is partly, we think, a reflection of the genuinely conceptually challenging nature of evolutionary theory. As we show (we hope) in the text, evolutionary theory really poses a striking compound of conceptual and empirical problems. But it is partly a historical accident, too. We have no doubt that there are similar problems in ecology, developmental biology, and molecular biology (at least), and we hope to have done at least a little to extend the reach of philosophy of biology into those areas.

Second, the title: We chose the title because it was fun. And philosophy of biology is fun. The living world is splendid and bizarre — far more bizarre than we, at least, could have imagined — and the conceptual problems posed in understanding it are wonderfully intriguing (and important, as we argue in chapter 1). We hope this book shows that. We nurture the illusion that it will both manifest our relish in the subject and perhaps infect others with the same disease.

The structure of the book is, we hope, evident from the analytic table of contents. Part 1 sets out the scope of the project. Parts 2–4 work through the core debates, as we see them, in evolutionary theory and associated branches of biology. In part 2 genes are at center stage: we discuss both the idea that evolutionary history is really, fundamentally the history of gene lineages and the  {xiii}  relationship between the evolutionary and molecular understanding of genes. In part 3 the focus changes to organisms, groups, and species. An important connecting thread is the question of whether groups and species play a role in evolution importantly like that played by organisms. Natural selection is central to part 4, for that part is on evolutionary explanation, and the key controversy about evolutionary explanation is the role of selection. So in a sense parts 2–4 are the heart of the book. Part 5 takes up human evolution, and more particularly, the sociobiological debates and their relatives. Apart from the intrinsic interest of this subject, many of the issues about the nature of evolution and natural selection are nicely exemplified through their application to humans. Part 6 winds up the show. We here attempt to put the central debates about the nature of evolutionary processes and patterns in a broader context by asking whether the characteristic patterns and processes of life on earth are likely to be features of any living world.

We have tried to write a book for three audiences. We wanted a book that would be accessible both to biology students with little or no philosophy and philosophy students with little or no biology. So we have used as little technical jargon as possible. When we have used specialist terminology from either discipline we have explained it in the text (usually immediately after the term's introduction) and, often, included it in the glossary. We have also made fairly liberal use of boxes in the text to discuss and explain more technical material. We have, however, tried to write the text so that no box is essential to following the flow of the argument. So readers should be able to skip the boxes if they like without losing the thread of the ideas. Many of the issues discussed in the book interconnect, one with the other. We have tried to help the reader follow these connections with parenthetic guides; for instance, “(5.3)” would indicate that the issue in play will be, or was, discussed further in section 5.3. Finally, we have provided “Further Reading” sections at the end of chapters 2-15 to introduce and orient newcomers to the literature.

So we hope this book is accessible to both philosophers and biologists without previous experience of the other area. Our third intended audience is, of course, our peers. This book is not a view from nowhere. It's an introduction to philosophy of biology from our own perspective on the discipline. So it contains our own assessment of what matters and what does not — of what is central and what is peripheral. That perspective is not widely shared, for we are products of a hybrid zone (displaying, we hope, hybrid vigor rather than hybrid sterility). Our take on evolution integrates important elements of the adaptationist, gene-centric conception of evolution associated with the likes of Maynard Smith, Williams, and Dawkins with elements of the pluralist, hierarchical conception  {xiv}  associated with Gould, Lewontin, and Eldredge. At the very least, we would like to convince others in the field that the space of viable options is larger than they might have supposed.

This book took a lot of writing, and we got a lot of help with that writing. First we would like to thank David Hull and Susan Abrams for their initial enthusiasm and continued support for the project. Second, we owe a lot to the opportunity to talk biology and philosophy of biology, over many years and on many occasions, with the following: Russell Gray, Peter Godfrey-Smith, Susan Oyama, GeofFChambers, David Hull, Karen Neander, Michael Hannah, David Braddon Mitchell, and Lenny Moss. They helped to provide the intellectual matrix from which this book has grown. Third, Peter Godfrey-Smith, Geoff Chambers, David Hull, Elliot Sober, Richard Francis, and two University of Chicago Press reviewers read and commented extensively on the semi-final manuscript. To them we owe much: thanks (not enough; if you're lucky you might get a beer as well). We thank Dan McShea, Susan Oyama, David Sloan Wilson, Alan Musgrave, James Maclaurin, Mike Dickison, Karola Stotz, Werner Callebaut, and Annemarie Jonson for reading and commenting on sizeable chunks of that same draft. We have three more specific thanks to give. First, we shamelessly borrowed, though with permission, the title of chapter 1 from R D. Gray andj. L. Craig, “Theory really matters: Hidden assumptions in the concept of habitat requirements” (1991). Second, chapter 4 owes a lot to Griffiths's collaborators on other publications, Robin D. Knight and Eva M. Neumann-Held. Third, chapter 12 owes much to David Braddon Mitchell.

There are some equally valuable nonintellectual inputs to acknowledge. Grif-fiths's thanks go to his former home, the University of Otago, for the outstandingly supportive research environment in the Department of Philosophy and for Richard Briscoe's valuable services as research assistant. Also to his present home, the University of Sydney, where he taught two courses based around this book and employed another indefatigable research assistant, Ross West, who prepared the illustrations.

Sterelny inflicted numerous extraordinarily rough drafts of various chunks of this book on students at Victoria University of Wellington in 1995 and 1996 and at the California Institute of Technology, also in 1996. He thanks them for suffering so patiently. He also thanks the Philosophy Department, Monash University for hospitality and support in 1994; the Philosophy and Law Program, RSSS at the Australian National University for similar hospitality and support in 1995, and Caltech for providing a home in 1996. His base institution, Victoria University of Wellington, has supported the project in many ways. It provided a grant for research assistance in 1997, which enabled him to employ James Mansell, who worked with great intelligence and enthusiasm in finding and  {xv}  tracking down references (thanks, James). It granted leave to visit the ANU in 1995 and, for a more extended period, Caltech in 1996. Most importantly, it remains a civilized and supportive environment in which to work. Finally, he would also like to thank Melanie Nolan for her (mostly) tolerant attitude to his various preoccupations with biology, preoccupations especially marked in the final burst of writing and rewriting this work.

Kim Sterelny, Wellington, New Zealand

Paul Griffiths, Sydney, Australia

Glossary

actual sequence explanation an explanation that characterizes events in fine detail, so that substituting other similar events would make the explanation invalid. See robust process explanation.

adaptation a feature of an organism whose presence today can be explained by the fact that it served some useful purpose in previous generations and hence helped some organisms to reproduce more than others. A cat's claws, for example, are adaptations for catching prey.

adaptive contributing positively to the current fitness of the organism that possesses it.

adaptive radiation a process by which, if the members of a species find themselves in vacant territory (by being the first to reach an island, by surviving an extinction event, or by invading a new type of habitat), their descendants, over evolutionary time, often diversify into many new species. Some of these will make their living in ways very different from the founding species.

allele an alternative form of a gene. Genes are located at particular regions of a chromosome known as loci (singular: locus). In a given population and at a given locus there may be several alleles.

amino acids the building blocks of polypeptides and hence ofproteins. One amino acid corresponds to one codon in the genetic code.

analog code a system in which a range of continuous values of a variable in the receiver represent continuous values of a variable in the sender

analogous traits see homologous traits

arms race a competitive ecological interaction between two species as a result of which each becomes better adapted to cope with the presence of the other,

arthropods a phylum of metazoans with a segmented body and an exoskeleton divided into jointed units. Insects and crustaceans are living examples.  {384} 

Bauplan (plural: Bauplane) the fundamental body plan of a group of related species; the basic layout manifested in various forms in these organisms. Also known as type. The persistence of body plans over long periods of evolution and through many episodes of speciation is known as the unity of type.

biogeography thestudy of the distribution of plants and animals across the globe.

biological determinism the view that important features of human psychological or social organization are in some way “fixed” by human biology. Different accounts of what and how characteristics are fixed generate different variants of biological determinism.

biota the totality of living things in a region.

chromosome a long DNA molecule that is wound around supporting, structural proteins; found in eukaryotes.

clade a group of species and their common ancestor; hence a segment of the tree of life (derived from the Greek word for “branch”). See also monophyletic.

clone a sequence of identical copies of some biological entity. Since no two biological entities are strictly identical — alike in every respect — describing a sequence as a clone implies a judgment about important similarities. Usually, genetic identity is the identity in question, and so clones of organisms arise only through asexual reproduction.

codon a group of three nucleotides in the genetic code. One codon specifies one amino acid, the unit from which proteins are built. Some codons signal the beginning and end of a gene rather than specifying an amino acid.

conspecific an organism of the same species as the one under discussion.

crossing-over a process that occurs during meiosis in which homologous chromosomes cross over and recombine, so that a part of each chromosome is exchanged with the other, before the chromosomes split into different gametes. Hence a gamete can have a sequence at a locus different from that of either parent.

cumulative selection selection acting repeatedly on a population. A new adaptation will evolve only as the result of many generations of selection preserving the favored feature and, in partnership with the mechanisms of variation, gradually enhancing it. Cumulative selection is much more powerful than single-step selection.

derived trait see primitive trait

digital code a system in which discrete states of the receiver represent discrete states of the sender.

diploid having two versions of each chromosome; if the organism is sexual, one of these comes from each parent.

disparity the variety or range of biological forms manifested at a particular time. Disparity is often conceptualized through spatial metaphors. Gould, for example, thinks of  {385}  "morphospace” as the array of all possible ways organisms could be physically organized. Disparity would then be the chunk of morphospace colonized at a particular time. It is controversial whether disparity can be measured in any objective way.

dispersal the distribution of plants and animals as a result of their own movement or that of their gametes.

diversity the number of species extant at a particular time.

dominant the relationship of one allele, A, to another, a, at the same locus when the heterozygote Aa has the same phenotype as the homozygote AA. The other allele, a, is said to be recessive if the phenotype of the homozygote aa is distinct from the Aa phenotype. Because the Aa phenotype can differ from both AA and aa, the dominant/recessive distinction is not exhaustive.

eliminativism the idea that the processes and entities mentioned by a theory can be shown not to exist by refuting that theory

epistasis an interaction among genes in which the effect of an allele at one locus depends on which alleles are present at some other locus.

epistemology the theory of knowledge and its nature. For example, an epistemologi-cal, or epistemic, question about biology is a question about how that biological fact is known.

ethology the study of animal behavior under its normal ecological conditions (as opposed to unusual laboratory conditions) and from an evolutionary perspective

eugenics the improvement of human fitness through selective breeding

eukaryotes organisms built from complex cells that have a discrete nucleus and much other cellular machinery, typically including mitochondria and (in plants) chloroplasts.

eusociality a form of group life in extended families in which some members of the group become specialized for reproductive functions, and other members of the group give up reproduction entirely. These nonreproducing animals live as members of a sterile worker caste (or castes), and are often physically very different from one another and the reproducing animals despite not being genetically distinct from them.

exaptation an adaptive trait whose current adaptiveness is not due to the same effect on fitness by virtue of which it was initially favored by natural selection

exobiology the biology of life on other planets.

exon see reading sequence

fitness a measure of the ability of a gene, organism, or other biological unit to reproduce itself.

frequency-dependent selection selection in which thejitnessofa. trait depends on the proportion of other, competing phenotypes in the population as a whole.  {386} 

function the purpose of a biological trait; what it is for.

Gaia hypothesis the idea that the biota of the entire earth constitutes a single super-organism.

game theory the mathematical study of competitive interaction. In evolutionary “games,” the players are organisms of alternative design, and their “payoffs” are increases in their fitness.

gametes sex cells. Gametes are haploid, having half the usual chromosome complement, and fuse in sexual reproduction to form a diploid cell Sperm, ova, and pollen are all gametes.

gene a unit of heredity. Genes have no uncontroversial definition; however, almost everyone accepts that they are, or include, DNA sequences of some kind. Reading sequences are commonly regarded as the paradigm genes.

gene pool the totality of genes in a breeding population or species.

genome all the genes of one organism.

genotype a synonym for genome; sometimes used more narrowly as a specification of all the genes an organism has at a specific locus or set of loci.

germ line the cell lineages in a multicellular organism that can potentially give rise to sex cells or gametes. See somatic line.

grade a type of biological organization. The same grade can potentially be found in several different clades.

group selection natural selection operating on groups of organisms

haplodiploid genetic system a genetic system in which females grow from fertilized eggs and have genes from both parents and are thus diploid, but males grow from unfertilized eggs and are haploid. Males have no father and have no sons. They have a random selection of one from each of their mother's pairs of chromosomes (perhaps modified by crossing-over), and they transmit all their genes to their daughters. Ants, bees and wasps use this system.

haploid having a single set of chromosomes.

heritability a measure of the probability that an offspring will share a trait possessed by its parent.

heterozygous see homozygous

homeostasis the process by which an organism maintains physiological variables, such as temperature and salinity, within acceptable limits. Sometimes used to refer to feedback processes more generally.  {387} 

homologous traits traits that taxa have in common through inheritance from a common ancestor. These contrast with analogous or homoplastic traits, qualitatively similar traits that have evolved independently.

homoplastic traits see homologous traits

homozygous having two alleles at a locus on a chromosome that are identical. When the alleles are different, the organism is heterozygous.

inclusive fitness see kin selection.

independent assortment, law of one of Mendel's laws, which states that the probability of a gamete receiving a particular allele at one locus is independent of which allele it receives at another locus. It is false when the two loci are on the same chromosome (gene linkage).

interactor a theoretical unit consisting of structures built as the result of the influence of a replicator (such as a gene) or replicators in development and acting so as to assist the reproduction of the replicator(s) responsible for its production. See also phenotype.

intron see reading sequence

kin selection the process of ensuring the presence of copies of one's distinctive genes in the next generation by helping one's relatives to breed, since they are likely to share those genes. A trait is kin-selected if it evolves by causing organisms to assist their relatives.

Lamarckian evolution a theory proposing that characters acquired during the lifetime of an organism can be passed on to that organism's offspring.

lineage a sequence of ancestors and descendants; parents and offspring.

linkage the tendency of two genes to be inherited together (thus violating the law of independent assortment). Genes on the same chromosome are linked, and the closer together their loci, the tighter their linkage; that is, the higher the probability that if one is inherited, the other will be. The closer genes are, the less likely they are to be split apart by crossing-over.

locus (plural: loci) the position on a chromosome occupied by a particular gene.

meiosis the type of cell division that gives rise to gametes, in which cells divide to form new cells with half the number of chromosomes. It contrasts with mitosis, cell division in which the daughter cells have the same chromosome number as the mother cell.

meiotic drive gene an allele that has an effect through which it has a greater than 50% chance of making it to a gamete when these are formed through meiosis (violating the law of segregation). Such alleles may spread even if they have adverse effects on an organism's fitness.  {388} 

memes postulated units of cultural inheritance, intended to be analogous to genes.

Mendelian genetics the discipline that studies heredity by performing breeding experiments and observing the effect of crossing organisms with different characters on the characters manifested in their ofl&pring. Also known as classic genetics or transmission genetics. Contrasts with molecular genetics, which studies the physical nature of the units of heredity.

messenger RNA (mRNA) the RNA sequence transcribed from a gene and later translated into protein. See reading sequence.

Metazoa the animals; a kingdom of life characterized by multicellularity, cells organized into tissues, an alimentary canal, and a nervous system.

mitochondria organelles within eukaryote cells that have their own DNA, reproduce themselves by splitting, and are inherited in the cytoplasm of the egg (hence only from the mother). They play a critical role in the production of energy in the cell.

mitosis see meiosis

molecular genetics see Mendelian genetics

monomorphic see polymorphic

monophyletic containing an ancestral species and all, and only, its descendant species. More controversially, a single species is called monophyletic if it contains all, and only, the organisms descended from a single event of speciation or hybridization.

morph one of several different phenotypes found in a single population.

mRNA see messenger RNA

natural kind a category postulated to correspond to some real distinction in the subject matter being classified, rather than being an arbitrary way of classifying.

natural selection the process by which some traits come to predominate in a population, by virtue of superior mess, while others decline in frequency.

niche the ecological role played by a species in an ecosystem. The same species in different ecosystems can play different ecological roles and hence occupy different niches.

nucleotide one the chemical bases from which DNA is composed: adenine, thymine, guanine or cytosine; or of which RNA is composed (in RNA, uracil replaces thymine). See codon

ontology in philosophy, the study of what broad categories exist. Whether God exists, or whether minds are entities distinct from brains, are ontological questions. The ontology of a theory is the claims the theory makes about what exists.

phenotype the manifested morphology, physiology, and behavior of an organism; contrasts with the genotype, the total collection of genes that an organism carries.  {389} 

pleiotropic having effects on more than one trait.

polygenic affected by more than one gene.

polymorphic having more than one form simultaneously in a population. Contrasts with monomorphic traits, which are the same in each individual in a population.

polypeptide a molecule made up of many amino acids joined by peptide bonds. One or more polypeptide chains makes up a protein.

primitive trait a trait that a species inherits from an ancestor in an unmodified form. In contrast, a derived trait is a trait that has appeared for the first time in the species or group of species in question. Primitive traits need not be simple. For example, if we are considering a group of cave-dwelling creatures, the primitive trait may be the possession of functional eyes, and the derived trait vestigial, nonfunctioning ones.

process explanation see robust process explanation

prokaryotes single-celled organisms without a nucleus or mitochondria. The bacteria are one main subdivision of the prokaryotes.

proteins a class of very large molecules made up of polypeptide chains of amino acids that are central to the chemistry of life.

reading sequence a sequence ofDNA that is transcribed into messenger RNA (rnRNA), which is in turn translated into protein. Some sections of the rnRNA, called introns, are cut out and discarded before translation, leaving only the intervening exons. Hence not all the DNA in a reading sequence contributes to the final protein product.

realism in philosophy, the view that a particular entity exists and exists independently of humans, their conceptions, and their observations — that it exists objectively. For example, realism about species is the view that species exist independently of their recognition and classification by humans.

recessive see dominant

reduction (1) the controversial idea that later, superior theories can explain and treat as special cases earlier, inferior theories of the same subject matter. (2) the controversial idea that the processes and entities of a “higher-lever” theory, such as psychology or biology, can be explained in terms of the processes and entities of a “lower-level” or “more fundamental” science, such as physics. (3) The noncontroversial idea that theories of higher-level processes must not rely on causal mechanisms that are inexplicable or mysterious from the perspective of more fundamental lower-level theories.

replicator a theoretical unit of heredity and selection; an entity that makes copies of itself and may cause the existence of an interactor or vehicle.

robust process explanation an explanation that characterizes events in very broad terms, so that the explanation remains valid when other, similar events are substituted for those that actually occurred. See actual sequence explanation.  {390} 

segregation, law of one of Mendel's laws, which states that the two alleles are separated in the formation of the gametes (sex cells), with each gamete receiving only one allele. See meiotic drive gene.

segregation distorter gene see meiotic drive gene

selection see natural selection

sociobiology the study of the evolution of the social behavior of animals. This term is sometimes used more narrowly to refer to the theory of the evolution of human social behavior.

somatic line that part of the organism consisting of cell lineages that are unable to give rise to sex cells (gametes). See germ line.

species the smallest taxa mentioned in a system of biological classification. Species are sometimes thought of as the units within which a single evolutionary process unfolds.

taxon (plural: taxa) a group of organisms recognized in biological systematics (taxonomy). Taxa are traditionally organized into a hierarchy of species, genera, families, orders, classes, and phyla.

transcription the production from a reading sequence of DNA of a matching sequence of messenger RNA (mRNA)

translation the production from a transcript of mRNA of a protein (a chain of amino acids)

type see Bauplan

unity of type see Bauplan

vehicle a slightly more controversial term for an interactor, carrying the implication that the replicator is the core unit of the evolutionary process.

vicariance the distribution of plants and animals as a result of geological processes. Contrasts with dispersal.

viviparous giving birth to live young, rather than laying eggs.

Weissmanism the doctrine that there is a distinct germ line. True mainly in animals.