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This review appeared in Volume 4 (1) of The Semiotic Review of Books.
From Gaia to Selfish Genes. Selected Writings in the Life Sciences. Edited by Connie Barlow/Cambridge, MA: The MIT Press. 1991. 273 p. ISBN 0-262-02323-7.
In the final sentence of her preface to this anthology, Connie Barlow writes that while physics may have a claim on cosmology and the arts on our imagination, biology speaks to our vision of self, our sense of place on a planet teeming with life" (p.x). This remark elegantly gives voice to the conviction shared by all the contributors to this volume: Our sense of who we are, and of what it is to be or to have a self is not to be untied from what we take life to be and from our sense of place among the diversity of living things. The perspectives brought to this conviction by the contributing authors differ considerably, however, both in scale, ranging from the microbial to the genetic, cellular, ecological, and geological levels, and in philosophical orientation, from "holism" to "reductionism". The book thus provides a very good introduction to contemporary debates about the and evolution, as well as some of their wider philosophical implications.It has become commonplace to observe that the Darwinian theory of evolution by natural selection provided humanity with a new and unsettled sense of its place in nature in relation to the medieval and renaissance idea of the great chain of being. The Darwinian theory undermined the idea that animal species were fixed, immutable, and hierarchically arranged, and traced the origin of the human species as a contingent line of descent from earlier primates. Whereas the Darwinian framework thus revealed our contingent origins, the biologists whose work is represented in From Gaia to Selfish Genes have collectively extended the biological contingency of our place in nature into the even more intimate arena of self-identity and biological individuality. In some cases, such as James Lovelock's Gaia theory and Lynn Margulis's theory of symbiosis in cellular evolution, the effect is to challenge certain aspects of the Darwinian framework; in other cases, such as Richard Dawkins's theory of selfish genes, it is to extend even more radically the original Darwinian ideas.
According to the original Darwinian theory, evolution (the modification of organisms by descent) occurs because there is a variation among the traits or properties of individuals in a population, the traits are inheritable, and natural selection favours individuals that possess the more fitness-enhancing traits (those that enable individuals to survive and reproduce more successfully than other individuals in the population). The so-called modern synthetic theory of evolution is based on combining the Darwinian theory of evolution by natural selection with the genetic account of inheritance due to Mendel and the subsequent molecular account of genes as lengths of DNA.
One of the central concepts of the modern Darwinian theory is that of adaptation. An adaptation in the most immediate sense is a design or construction that matches more-or-less optimally some physical situation. For example, the fins of fishes are said to be an adaptation to an aquatic environment. Most evolutionary theorists do not construe adaptation in this way, however. Instead, they take adaptation to be the process of adapting linked to survival and reproduction. As Darwin himself knew, the environment is not static, but changing. Depending on the environmental changes, certain variants in the population will be "fitter" than others in the sense of being able to leave more offspring. Hence rather than organisms adapting themselves to a fixed environment, environmental changes involve the "selective pressures" that (blindly) direct the adapting process.
The Gaia theory, developed by the atmospheric chemist James Lovelock and the microbiologist Lynn Margulis, which provides the topic of Section I of From Gaia to Selfish Genes, builds on the Darwinian idea of environmental change in evolution, but deepens it in a way that implies a reformulation of the relationship between organisms and environment in evolutionary theory. When Lovelock and Margulis first put forward their proposal in the 1970's, they called it the Gaia hypothesis (Lovelock 1972; Margulis and Lovelock 1974). In Lovelock's words, "the Gaia hypothesis said that the temperature, oxidation state, acidity, and certain aspects of the rocks and waters are at any time kept constant, and that this homeostasis is maintained by active feedback processes operated automatically and unconsciously by the biota (the collection of living organisms)"(10).In the past twenty years they have expanded this hypothesis into a theory "that views the evolution of the biota and of their material environment as a single tight-coupled process, with the self-regulation of climate and chemistry as an emergent property"(Lovelock 1991, 30).
Lovelock's essay in this volume consists of excerpts from two of his books on Gaia (Lovelock 1979; 1988). The excerpts cover how Lovelock came to formulate his theory, evidence for Gaia, and his now famous "daisyworld" computer model. The model was designed to answer criticisms of the Gaia theory made by W. Ford Doolittle and Richard Dawkins, both of whom are also represented in this volume. They argued that Lovelock's hypothesis that the Earth's climate was regulated "by and for the biota" was teleological, implying impossible foresight and planning on the part of the biota. Lovelock's answer was to devise a computer model in which the competitive growth of light and dark daisy species alters the albedo (reflectance) of the planet's surface, thus changing the balance between the heat received from the Sun and that lost to space, and so regulating the temperature of the planet. The daisy world model thus demonstrates how one property of the global environment, temperature, can be regulated by an automatic, homeostatic mechanism realized by the biota.
In Lovelock's view, then, the material environment of life on Earth, which comprises the atmosphere, oceans, and surface geology, is a "biological construction...like a cat's fur, a bird's feathers, or the paper of a wasp's nest"(12). It is a nonliving extension of the activity of the biota that contributes to the maintenance of the global environment. Thus the material environment does not simply provide the selective pressures for evolution, as in classical Darwinian theory, for it is also moulded and shaped by the biota so that the two form a tightly coupled, planetary system. For Lovelock, this system constitutes the largest known biological individual: "The boundary of the planet...circumscribes a living organism, Gaia, a system made up of all the living things and their environment"(18).
The Gaia theory has certainly not gone without criticism in the scientific community. The main criticisms are due to Richard Dawkins and W. Ford Doolittle; those by Doolittle are reprinted in the volume. Doolittle's main point is that Gaia should not be accorded the status of a living system because it "is not a replicating individual, and has no coherent heredity"(235).Doolittle also argues that it is unlikely that the global self-maintaining mechanisms that Lovelock hypothesizes are the result of natural selection, and so, if they exist, are "accidental "(33).
The issues raised by these criticisms cut across evolutionary theory, theoretical biology, and the philosophy of science. For example, Doolittle's criticisms are based on the Darwinian framework in which reproduction and replication are taken to be the defining characteristics of life. The Gaia theory, on the other hand, regards metabolism, rather than replication, as the more central feature of living systems, and, as Freeman Dyson has argued (Dyson 1985), it is certainly possible to imagine metabolic systems that do not have the ability to replicate. Margulis, in a short excerpt in the book's final section, portrays the difference as one between a replication based approach to biological systems, whose leading exponent is Dawkins, and an alternative approach based on the theory of "autopoiesis" due to the biologists Humberto Maturana and Francisco Varela (Varela et al, 1974; Maturana and Varela 1980).
The aim of the theory of autopoiesis is to specify the organization that is necessary and sufficient to qualify a system as living. The specification is meant to cover living systems as they would exist anywhere in the universe; consequently it is abstract in the sense that it makes no reference to the contingent physical and chemical processes involved in living systems as we know them on Earth. According to the theory, living systems have a self-producing (autopoietic) organization: A living system is composed of a network of processes that simultaneously produce and realize the system as a unity.
The theory of autopoiesis was developed mainly with reference to the single bacterial cell, but in Margulis's view, Gaia too qualifies as autopoietic (p.237). This view is not shared by Varela, however; in his view Gaia is a biological individual that is "autonomous" but not autopoietic (Varela 1991). In any case, the important point here is not whether Gaia qualifies as autopoietic in the technical sense, but rather that autopoiesis provides a theoretical framework in which replication and reproduction do not enter as defining (i.e.,necessary) features of living systems. Replication and reproduction both require a preexisting system to be replicated or reproduced, and so they are logically and operationally secondary to the establishment of the unitary system via the processes of autopoiesis.
Evolution too is operationally derivative, for it requires reproduction and the possibility of variation. Hence replication, reproduction, and evolution do not enter into the defining organization of a living system; they are rather complications of autopoiesis that must arise in the course of the autopoietic process.
Given the framework provided by the theory of autopoiesis, then, Gaia's status as a biological individual is not impugned by the fact that it is not a replicating individual. Yet care should be taken in asserting, as Lovelock does, that "evolution concerns Gaia, not the organisms or environments taken separately"(10). The point here is that organism is and material environment are tightly-coupled in evolution such that they form a planetary biological individual. But it does not follow that evolution pertains to the level of that individual per se, in contrast to the components the individual comprises. Evolution pertains not to individuals taken singly, but to populations of differentially reproductive individuals (at whatever level of selection). Gaia, however, in contrast to its component biological systems, is a single entity that does not replicate or reproduce, and so Doolittle is right to say it has no coherent heredity. Consequently, Gaia does not, strictly speaking, evolve, for it has like any individual only a history of change. It might therefore be preferable, l think, to talk about the ontogeny, rather than the evolution, of Gaia. If Gaba is an individual with its own ontogeny, then it not only has its own distinctive emergent properties, as do you or I in relation to the cells that compose us; It also contains and provides the environment for us, as do we for the bacteria in our intestines. Perhaps the most remarkable aspect of this idea, in relation to our familiar anthropocentric habits of thought, is its scale. As Lovelock writes in an essay to be found in another anthology published at the same time as Barlow's (Thompson 1991): "Life is a planetary-scale domain...There cannot be sparse life on a planet. It would be as unstable as half of an animal. Living organisms have to evolve with their planet to the stage of emergence when they are able to regulate their planet, otherwise the in-eluctable forces of physical and chemical evolution would render it uninhabitable" (Lovelock 1991 41).
In Section II of the book, entitled "Merged Beings", the scale shifts from the planetary domain to the equally remarkable microcosms, focusing on microbiologist Lynn Margulis's theory of symbiotic evolution. Margulis holds that symbiosis is a basic mechanism of evolutionary change; she is best known for building a case over many years for the theory that nucleated cells originated from symbioses among bacterial cells. Some popularizers have interpreted her views on symbiosis as anti-Darwinian, but this seems mistaken because Margulis's arguments always appeal to the idea that symbiosis enhances the fitness (reproductive success) of the organisms involved, thus making symbiosis entirely compatible with natural selection. What Margulis's work really challenges, it seems to me, is the conception of the biological individual that has been presupposed in the modern synthetic theory of evolution: Organisms have been conceived as discrete and unambiguously definable individuals, rather like the atomic agents of classical social theory. Symbiosis, however, implies that, in Margulis's words, "All of us are walking communities. Every plant and animal on Earth today is a symbiont, living in close contact with others"(50).
One of her favourite examples is a species of desert termite. In its hindgut live millions of single-celled organisms and attached to the surface of each live thousands of spirochete bacteria. Inside these bacteria live still other kinds of bacteria. The bacteria are needed for the termite to digest wood and so without them it would starve. Once the termite has digested the wood, it expels methane gas into the air. Methane regulates the amount of oxygen in the atmosphere and the methane-producing bacteria found in termites and other animals account for a significant proportion of the Earth's atmospheric methane. Where among these many layers of activity, which comprise even the tightly-coupled atmospheric and biotic levels of the Gaia theory, are we to locate a privileged individual? As Margulis puts it: "Really, the individual is something abstract, a category, a conception. And nature has a tendency to evolve that which is beyond any narrow category or conception"(59).
Section II of From Gaia to Selfish Genes also includes two other contributions collected into a chapter called "Blurred Bounds of Individuality." The first is a very useful selection from Julian Huxley's classic work, The Individual in the Animal Kingdom, written in 1912 but still quite pertinent to contemporary discussions. The second consists of short excerpts from two recent works on biological individuality, one on clonal growth (Jackson et al.1985) -- the formation of individuals that are genetically identical -- and the other devoted to the evolution of individuality (Buss 1987).
A rather different vision from Margulis's of how the biological individual is something abstract emerges from Richard Dawkins's "selfish gene" theory presented in Section VI. For Dawkins, "individuals are not stable things, they are fleeting"(211) because they are the vehicles for the potentially immortal replicating molecules that form the genetic units. In Dawkins's notorious formulation: "We are survival machines-- robot vehicles blindly programmed to preserve the selfish molecules known as genes"(195).
The argument presented in the first edition of Dawkins's The Selfish Gene (Oxford University Press, 1976) was based largely on evidence already familiar to the biological community. But in 1980 two articles appeared in Nature that have been taken to provide evidence for Dawkins's idea that natural selection acts upon the gene (rather than the individual organism or the population) and that an organism is simply "DNA's way of producing more DNA." The articles, one by W. Ford Doolittle and Carmen Sapienza, the other by Leslie Orgel and Francis Crick, are both reprinted in part in this volume. The articles reported finding so-called "junk DNA" or "selfish DNA," excess genetic material that is not transcribed into proteins, and so appears to serve no useful role for the organism, yet continues to be replicated with each replication of the whole chromosome.
Junk DNA provides a fascinating example of how the significance given to an empirical discovery depends on one's background theory and philosophical assumptions. Consider the terms that are used to refer to this kind of genetic material. "Junk DNA" is implicitly organism-centred because it refers to the fact that the DNA is not transcribed into proteins and confers no selective advantage to the organism. "Selfish DNA ," on the other hand, is explicitly gene-centred because it conveys the idea that the DNA is a unit of evolution and selection In its own right. Yet in characterizing the solely replicative activity of this type of DNA as "selfish" or "self-preserving" within the intracellular environment, the term "selfish DNA," far from conveying how the individual is something "fleeting," actually reinforces the reified and profoundly unbiological conception of the individual to which Dawkins wishes to object. As Stephen Jay Gould notes in a short passage reprinted in this volume:
Selfish DNA is about the worst possible name for the phenomenon, for it records the very prejudice that the new structure of explanation should be combatting: the exclusive focus on bodies as evolutionary agents. When we call repetitive DNA "selfish", we imply that it is acting for itself when it should be doing something else namely, helping bodies in their evolutionary struggle. But are bodies the only kind of legitimate individuals in biology? Might there not be a hierarchy of individuals, with legitimate categories both above and below bodies: genes below, species above? (231).
The structure of Dawkins's theory, then, is actually deeply wedded to the concept of discrete and unambiguously definable individuals, and so, contrary to Dawkins's own intentions, shows up his demystifying rhetoric about biological individuality as superficial and misleading. In contrast, Margulis's work on symbiosis emerges as the truly radical reevaluation of biological individuality, for it questions in a relentlessly thorough fashion -- both biologically and conceptually -- the idea that there is a privileged individual anywhere in the nested hierarchy of biological and ecological systems. Yet precisely by thoroughly "decentring" the biological individual in the context of evolutionary symbiosis, Margulis is able to provide what to me is a far more compelling biological vision of ourselves as Gaian-embedded, symbiotic communities than Dawkins's dreary and lifeless vision of lumbering robots at the mercy of selfish genetic homunculi.
In addition to the Gaian and selfish gene sections of this volume are four other sections that I have not discussed in this review. Section III is devoted to a broad discussion of methodological issues about systemic and hierarchical, in contrast to reductionist, approaches in biology and ecology. These kinds of issues are particularly important and some have arisen in this review. Unfortunately, this section of the book is rather weak. It is organized into two chapters, one devoted to the thought of Arthur Koestler and the other to the "General Systems Theory" of Ludwig von Bertalanffy. The excerpts from Koestler are enjoyable, and his concept of a "holon" -- a whole that is also a part -- remains genuinely useful in the context of contemporary debates. In contrast, the excerpts from von Bertalanffy amount mostly to generalizing advertisements for his conception of a universal science of systems. I am certainly sympathetic to so-called "systemic" and "holistic" forms of explanation (though i also think that only extreme versions of holism and reductionism are incompatible), but in my estimation von Bertalanffy's work has been largely superseded by more contemporary research in the fields of complexity and evolving hierarchical systems.
Section IV is devoted to game theory and the evolution of cooperation; it focuses on the work of mathematician and political scientist, Robert Axelrod. The topic of Section V is the field of sociobiology as formulated by E.O. Wilson; it contains excerpts from Wilson's writings as well as criticisms of sociobiology by other scientists. Section VII, the final section of the book, contains short essays designed expressly for the volume by Doolittle, Margulis, Wilson, and others.
From Gaia to Selfish Genes is generously illustrated and contains editorial remarks inserted between and within the sections by Barlow. The remarks are informative and in the main are unobtrusive, making the volume useful both as an introduction and as a coffee-table book conducive to browsing. The volume would also serve well in undergraduate courses in the philosophy of science and seminars in the philosophy of biology, especially when read in conjunction with more theoretical works on the debate about units of selection (e.g.,Brandon and Burian 1984), as well as anthologies that present a more extensive scientific and philosophical treatment of the Gaia theory (Thompson 1987, 1991).
Brandon,R. and R. Burian (eds.).1984. Genes, Organisms, and Populations: Controversies over the Units of Selection. Cambridge, MA: Bradford Books/The MIT Press.
Buss, L.W. 1987. The Evolution of Individuality. Princeton: Princeton University Press.
Dyson, F.1985. Origins of Life. Cambridge: Cambridge University Press.
Jackson,J.B.C., L.W.Buss, and R.E.Cook(eds.).1985. Population Biology and Evolution of Clonal Organisms. New Haven: Yale University Press.
Lovelock,J.E.1972. "Gaia as seen through the atmosphere." Atmospheric Environment 6:579-80.
Lovelock,J.E.1979. Gaia. A New Look at Life on Earth. New York: Oxford University Press.
Lovelock,J.E.1988 The Ages of Gaia. New York: W.W. Norton & Company.
Lovelock,J.E.1991. "Gaia: a planetary emergent phenomenon." In Thompson (1991).
Margulis,L. and J.E.Lovelock. 1974. "Biological modulation of the Earth's atmosphere." Icarus 21:471-89.
Maturana,H. and F.J. Varela. 1980. "Autopoiesis and Cognition. The Realization of the Living." Boston Studies in the Philosophy of Science, V.43.Dordrecht;D.Reidl.
Thompson,W.l.(eds.)1987. Gaia. A Way of Knowing. Political Implications of the New Biology. Hudson,NY: The Lindisfarne Press.
Thompson,W.l.(eds.)1991. Gaia.Emergence: The New Science of Becoming. Hudson,NY: The Lindisfarne Press.
Varela,F.J.1991. "Comments on Lovelock." In Thompson (1991).
Varela,F.J.,Maturana and R.Uribe. 1974. "Autopoiesis: the organization of living systems, its characterization and a model." Biosystems 5:187-195.
Evan Thompson is Assistant Professor in the Philosophy Department at Concordia University. He received his Ph.D. from the Philosophy Department at the University of Toronto where, during 1991-92, he also taught as an Assistant Professor. He has pursued extensive research at the Centre de Recherche en Epistemologie Appliquee(CREA) in Paris, and has held a SSHRCC Postdoctoral Fellowship, first in the Philosophy Department at the University of California at Berkeley, and then at the Center for Cognitive Studies at Tufts University. He is the author, with Francisco J. Varela and Eleanor Rosch, of The Embodied Mind: Cognitive Science and Human Experience (The MIT Press,1991), and of Colour Vision. A Case Study in Cognitive Science and the Philosophy of Perception (Routledge Press, forthcoming).