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Eylem Cetin Group moderatorThe company name is only visible to registered members.The Synergism Hypothesis
The Synergism Hypothesis
On the Concept of Synergy and It's Role in the Evolution of Complex Systems
JOURNAL OF SOCIAL AND EVOLUTIONARY SYSTEMS, 21(2), 1998
"Generalizations derived from a juxtaposition of facts are not fruitful unless some conceptual, theoretical scheme guided the generalizations and, incidentally, the selection of facts..."
Anatol Rapoport
"Experiments unguided by an appropriate theoretical framework usually amount to little more than ‘watching the pot boil'... We need experiments to inform theory, but without theory all is lost."
John H. Holland
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INTRODUCTION
It is one of the paradoxes of our age that as the tools of scientific research have grown ever more powerful -- from positron emission tomography to electron microscopy, nuclear magnetic resonance and massively parallel computers -- the phenomena we are able to investigate (and their causal dynamics) seem to grow ever more complex. The relentless reductionism of particle physics, polymer chemistry, molecular biology and neurobiology, among other disciplines, has not (so far) revealed the decisive "mechanisms" or underlying "laws" of the phenomenal world. Instead, the "microcosmos" (to borrow Lynn Margulis's term) displays profound complexity, interactionism, interrelatedness and, not least, historical specificity.
It has been suggested that our era should be called "the age of complexity." While this sobriquet (or epithet, depending on your values) may be appropriate, complexity is certainly not a newly discovered aspect of the natural world.1 The debate over "wholes" and "parts" (or holism and reductionism) can be traced at least to Periclean Athens and to the writings, especially, of Aristotle. Although scholars these days have a propensity for forgetting their forebears, over the course of this century there have been successive waves of holistic and reductionist theorizing -- a sort of transgenerational dialectic -- in which many of our most distinguished scientists have played a part. After reaching an apogee of sorts with the imposing theoretical edifice of the 19th century polymath Herbert Spencer (1892/1852, 1874-82), holistic theorizing was all but banished by the supporters of Darwin's theory, and (later) of "Weismannism" and "mutation theory," at the turn of this century. However, in the 1920s holism (especially the concept of "emergent evolution") reappeared, thanks to the writings of C. Lloyd Morgan (1923), Jan Smuts (1926), and William Morton Wheeler (1927), and others. Following another haitus in the 1940s, holism recast as "systems theory" was revived again in the 1950s with the emergence of the systems sciences (see especially Ludwig von Bertalanffy, 1950, 1956, 1968; Kenneth Boulding 1956, 1977; H. Ross Ashby 1958; Anatol Rapoport 1968; Arthur Koestler and John R. Smythies 1969; Ervin Laszlo 1972; and James Grier Miller 1995[1978].) Nowadays, systems theory -- which is partial to cybernetics and feedback models -- seems to have been temporarily eclipsed by "complexity theory" -- which is partial to chaos models and hypotheses of "self-organization." (Stuart Kauffman, 1995, calls it "order for free.") However, the two disciplines are really close kin.
What sets the present era apart is the fact that the scientific enterprise seems to be in the process of bridging the theoretical chasm between holism and reductionism; there seems to be a growing appreciation of the inextricable relationships between (and within) wholes and parts, and between various "levels" of organization, relationships which necessitate multi-leveled, multi-disciplinary, "interactional" analyses. (See Corning 1983; Kline 1995; also Polanyi 1968; Anderson 1972; Ghiselin 1981, 1997; Eldredge 1985; Buss 1987; Grene 1987; Maynard Smith and Szathmáry 1995; Miller 1995/1978.) Witness Francis Crick (1994), a Nobel Laureate (for the double helix) and a reformed arch-reductionist, who now embraces the phenomenon of emergence in his recent book on the nature of "consciousness" (see below). Indeed, the very terms "mechanism" and "laws" seem increasingly to be naive formulations in light of the enormously complex, dynamic processes that we can observe (and model) in ever more sophisticated ways. Consider just a few examples: quantum non-locality and quantum entanglement in physics; the highly conserved homeobox domain, consisting of some 60 amino acids, which plays a key role in morphogenesis; the awesome functional organization of the human immune system, which includes at least nine different subsystems; the elaborate cortical substrate of human vision, which involves many millions of neurons and at least 20 distinct visual areas; the intricate relationships and multi-leveled feedback processes associated with even a relatively simple ecosystem; the daunting interconnections between world population growth, technology, economic activity and vested political interests and rivalries, on the one hand, and the problems of environmental pollution, habitat destruction and resource depletion.
There have been many efforts in recent years to gain greater theoretical control over this overwhelming complexity. Best known, perhaps, are the non-linear dynamical systems models that are capable of exploiting the computing power of super-computers. (See Yates et al.,1987; Kauffman 1993, 1995; Holland 1992, 1995; TK and TK.) This has proven to be a fertile and productive enterprise, and we can at present barely glimpse its ultimate potential. For instance, computer scientist John H. Holland is involved in an ambitious attempt to model the evolution, aggregate behavior (emergence) and anticipation (purposiveness and cybernetic feedback processes) of what he characterizes as "complex adaptive systems." (See also Chauvet, 1993.)
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ON THE CONCEPT OF SYNERGY
Here we will describe a complementary approach. It involves, in effect, a conceptual revisioning of the phenomenal world -- a paradigm shift -- which directs our attention to an underlying causal principle that is concerned with structural and functional relationships of various kinds and with the concrete consequences, or effects that they produce. Albert Einstein many years ago observed that "we should make things as simple as possible, but not simpler." Theoretical simplifications, or generalizations, may serve to identify key features, common properties, or important relationships among various phenomena. Equally important, a concept which encompasses a broad range of phenomena may also serve as the anchor for a theoretical framework which, in turn, may catalyze specific hypotheses, predictions or tests.
One example is the concept of natural selection. Evolutionists often speak metaphorically about natural selection (as did Darwin himself) as if it were an active selecting agency, or a mechanism. But in fact natural selection is an "umbrella" category that refers to whatever functionally-significant factors (as distinct from, say, stochastic or teleological influences) are responsible in a given context for causing the differential survival and reproduction of genes, genic "interaction systems" (in Sewall Wright's term), genomes, groups, populations and species. Genes are the units that are selected, but it is the functional consequences of the genes that (by and large) determine their ultimate fate. (The "classical" population genetics definition of natural selection as a change in gene frequencies in a population is -- as Wimsatt, 1980, has pointed out -- inadequate because it focusses on the informational and "bookkeeping" aspect of a larger, iterative functional process.)
Accordingly, as a theory of evolutionary change natural selection makes no global predictions about the overall course of evolution or the future of any given species, in contrast with various "orthogenetic" or law-like theories of evolution. Nevertheless, the concept leads to many situation-specific explanations, predictions and postdictions about the properties of various organisms, about the relationships among species (and between any species and its environment) and about the causes of various directional changes through time.
Another example of an "umbrella" term is the concept of hierarchies. The basic principle was well understood by Aristotle, and by the 19th century taxonomists and evolutionists, but the term itself apparently traces to the turn of this century (reviewed in Grene, 1987). Today the term is used in a variety of ways, with each usage having its own theoretical connotations. (See the discussions in Weiss 1971; Pattee 1973; and the references for multi-levelled organization cited above.) Thus, the postulate of a taxonomic hierarchy, which entails a classification of various species into more inclusive groupings (genera, families, orders, etc.), also implies that a given species has certain characteristics and evolutionary relationships in common with (or different from) other species, both extant and extinct. The physiologists, in contrast, associate the term hierarchy with organelles, cells, tissues, organs, etc., a scheme which implies a nested set of functional parts-wholes relationships. Likewise, to political scientists a hierarchy refers to structured relationships of power, rule or authority -- to different "levels" of cybernetic (political) control. And when biologists Niles Eldredge and Stanley Salthe (1984) drew a distinction between "genealogical" and "ecological" hierarchies in nature, they were also implicitly making certain claims about the causal dynamics of the evolutionary process (see also Ghiselin 1981, 1997; Eldredge 1985; and Salthe 1985).
"Synergy" (from the Greek word synergos) is another such umbrella term. Although it is often overlooked, underrated, or misunderstood (or called by a different name), synergy is a ubiquitous and fundamentally important aspect of the natural world. (For an in-depth discussion, see Corning 1983; also 1995, 1996, 1997.) Synergy, broadly defined, refers to combined or "co-operative" effects -- literally, the effects produced by things that "operate together" (parts, elements or individuals). The term is frequently associated with the slogan "the whole is greater than the sum of its parts" (which traces back to Aristotle in The Metaphysics) or "2+2=5", but, as we shall see, this is actually a caricature, a narrow and perhaps even misleading definition of a multi-faceted concept. We prefer to say that the effects produced by wholes are different from what the parts can produce alone.
There are innumerable illustrations of synergy. One pointedly non-quantitative example has to do with pattern recognition, or what is referred to in psychology as gestalt phenomena (reviewed in Rock and Palmer 1990). The two-letter combinations PT, TP, RT, and TR, mean nothing to most of us (except perhaps to old salts of the World War Two era, who may remember the PT Boats). But if you add a vowel -- either an "o" or an "a" -- to each of these consonants, you will get the results shown in Table I below. The three-letter combinations in the table are now meaningful (at least to English-literate readers), although, interestingly enough, the combinations shown in column four are utilized only as acronyms, perhaps because they are more difficult to pronounce. (Some of these acronyms are "please turn over," "Parent-Teacher's Association," and "Rapid Transit Authority." No doubt there are others as well.)
TABLE 1: PATTERN RECOGNITION
POT TOP OPT PTO
PAT TAP APT PTA
ROT TOR ORT RTO
RAT TAR ART RTA
Unless you happen to be a fan of cross-word puzzles, you may not recognize in the table the more obscure words "tor" (rocky promontory) and "ort" (food scrap). This illustrates an important point about the nature of synergistic phenomena. Synergy refers specifically to the structural or functional effects that are produced by various combinations of things. In this case, it refers to the effects that the words produce in the reader's mind; it is not something that is inherent in the patterns themselves. Thus if a word evokes no mental image, it is at best an example of latent synergy.
There are obviously many different kinds of cooperative/synergistic effects. Some arise from linear or additive phenomena. Larger size, frequently the result of an aggregation of similar units, may provide a collective advantage. For instance, colonies of the predatory myxobacterium (Myxococcus xanthus) are jointly able to engulf much larger prey than any one or a few could do and, more important, are able collectively to secrete digestive enzymes in concentrations that would otherwise be dissipated in the surrounding medium (Bonner 1988; Shapiro 1988).
A variant of this type of synergy involves frequency or density-dependent phenomena. Brood parasitism in birds is a case in point. The effectiveness of this freeloading reproductive strategy depends upon, among other things, the availability of nest sites, the number of eggs laid by the "hosts" and the number of eggs laid by their parasites (Read and Harvey 1993). Density dependent effects are also involved in the well-known correlations between bacterial colony size and a bacterium's ability to cause infections or resist drugs (e.g., Staphylococcus aureus).
So-called "emergent phenomena" are a particularly important class of synergistic effects. (We restrict the term "emergence" to the subset of synergistic effects in which new physical "wholes" are synthesized.) Thus, stainless steel is an alloy of steel (itself an alloy) together with nickel and chromium, a combination which exhibits rust- and tarnish-resistance and increased durability. Duralumin, which is a compound of aluminum, copper, manganese and magnesium, combines the light weight of aluminum and the strength of steel. And the so-called super alloys comprised of nickel, cobalt and other elements are favored for jet engines and spacecraft because they can resist very high temperatures, high pressures and oxidation.
The "division of labor" (or, very often, various combinations of labor), a phenomenon appreciated by Plato and further articulated by Adam Smith and the classical economists, represents another important category of synergy. To illustrate, one important component of the reproductive machinery in living systems involves a division of labor and coordinated efforts of three different kinds of RNA -- Messenger RNA, Transfer RNA and Ribosomal RNA. Darnell et al., argue, in their textbook on molecular and cell biology, that "the development of three distinct functions of RNA was probably the molecular key to the origin of life" (1990: 88).
Among the many other examples of a division of labor found in nature, some of the most remarkable appear in very primitive life forms: bacterial colonies, eukaryotic protists, cellular slime molds, etc. One case in point involves Anabaena, a cyanobacterium which engages in both nitrogen fixation and photosynthesis, a dual capability that gives it a significant functional advantage. However, these two functional processes happen to be chemically incompatible; the oxygen produced by photosynthesis can inactivate the nitrogenase required for nitrogen-fixing. Anabaena has solved this problem by complexifying. When nitrogen is abundantly available in the environment, the cells are uniforn in character. However, when ambient nitrogen levels are low, specializaed heterocysts are developed which lack chlorophyll but which are able to synthesize nitrogenase. The heterocysts are then connected to the primary photosynthesizing cells by filaments. Thus, a compartmentalization and specialization of functions exists which benefits the "whole" (Shapiro 1988).
Synergy is also found in a variety of mutually enhancing or augmenting functional effects in nature. Hemoglobin, a tetrameric protein whose four monomers cooperatively bind oxygen, is one well-known example. (Indeed, there is an area of biochemistry called "cooperativity theory," which is focussed on the study of the many kinds of synergistic phenomena that occur at the biochemical level-- see Hill 1985.) Another example at the micro-level concerns the observed error rate in normal cellular DNA replication, which is remarkably low (about 10-10 to 10-8 per base pair) compared with the theoretical potential, given the ambient sources of decay, damage and copying errors of about 10-2. The explanation for this discrepancy is that it is the combined result of a complex set of mechanisms that "work together," including proofreading by DNA polymerases, methylation-instructed mismatch correction, enzymatic systems that repair or bypass potentially lethal or mutagenic DNA damage, processes that neutralize or detoxify mutagenic molecules, the regulation of nucleotide precursor pools and, of course, the redundancy achieved by double-stranded genetic material (Haynes 1991).
There is also in nature a broad category of what might be called "bioeconomic" efficiencies that are derived from cooperative behaviors of various kinds, such as joint environmental conditioning, cost and/or risk sharing, information sharing, etc. Thus, emperor penguins (Aptenodytes forsteri) are able to buffer themselves against the intense Antarctic cold by huddling together during the winter months in dense, heat-sharing colonies numbering in the tens of thousands. Experiments have shown that, in so doing, the penguins are able to reduce their individual energy expenditures by 20-50 percent (Le Maho 1977). Similarly, honey bees, through joint heat production or fanning activities as the need arises, are able to maintain the "core" temperature of their hives within a narrow range (Gould and Gould 1995). And Partridge (1982) and his colleagues have shown that fish schools, which can include the active coordination of behaviors, may be highly adaptive for individual members. For instance, the evasive maneuvers utilized by dwarf-herring against predatory barracudas dramatically reduce the joint risk of being eaten.
Information sharing (wittingly or otherwise) may be highly synergistic. Social insects and communally nesting birds frequently share information about food patches. Many animals engage in alarm calling, which may alert nearby members of their own and other species. And many flocking birds and herd animals share in the tasks -- and energy costs -- associated with scanning for potential predators (King 1955; Wilson 1975; Caraco 1975; de Groot 1980).
Another preliminary point about the concept of synergy is that it is value-neutral. Over the years various writers have equated the term with mutualism or even altruism. However, this is not correct. Synergy refers to combined effects of all kinds. These effects may be considered eufunctional (positive synergy), dysfunctional (negative synergy), or even neutral, depending on the context. For instance, the mutation-enhancing effects of gamma rays and metallic salts in combination might be viewed positively if you were a geneticist who wanted to enhance mutation rates in a laboratory study. By the same token, the synergies achieved by pack-hunting social animals (in terms of, say, capture efficiency or the size of the prey) may be viewed positively from the point of view of the predators but rather negatively from the point of view of their victims.
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A PAN-DISCIPLINARY PHENOMENON?
As noted above, synergistic phenomena can be found in many different disciplines. In some disciplines, the term synergy is used extensively. (A literature search of a data base for the biological sciences for the five-year period from 1991 through 1995 produced some 3,400 "synerg" references, concentrated for the most part in such "hard sciences" as endocrinology, neurochemistry, pharmacology, etc.) Yet in other biological disciplines, paradoxically, the term synergy is used sparingly, if at all. Consider sociobiology, for instance, which is primarily concerned with cooperative behaviors among conspecifics in nature. A highly organized social species, such as honey bees, army ants, or naked mole rats, exhibit many different forms of social synergy -- from joint thermoregulation to information sharing, cooperative foraging, mutual grooming, mutual defense, cooperative nest-building, etc. Nevertheless, these behaviors are typically characterized as "kin selection," or "reciprocal altruism," a "division of labor," "emergence," "mutualism" or simply "cooperation."
Likewise, various formal models of cooperation in sociobiology also implicitly depend on synergy. For instance, in the well-known Tit-For-Tat model of Axelrod and Hamilton (1981), mutual cooperation is rewarded with 6 points, while "defection" by one player is rewarded with 5 and mutual defection yields only 2 points. And yet, the dependence of this and other "game theory" models on synergy is seldom acknowledged.
It is not possible to provide here a detailed, discipline-by-discipline analysis of the many different kinds of synergy, and the terminology that is used to describe it. As an alternative, a selected sample of the scientific disciplines is presented in Table II, along with representative examples and some associated terminology. This is followed by a brief description of each example, with special reference to its synergistic aspects.
TABLE II: SYNERGY IN SELECTED
SCIENTIFIC DISCIPLINES
Scientific
Discipline Representative Example(s) Associated
Terminology
Quantum Physics Quantum Coherence holism, ordering
Physics Chaotic Phenomena emergence, interactions, attractors, order
Self-organized Criticality interactions, holism
Phase Transitions cooperative effects, symmetry, breaking
Thermodynamics Dissipative Structures order/disorder, low entropy, negative entropy, order, emergence
Biophysics Hypercycles cooperation, interactions, coordination, order, emergence
Chemistry Molecular Macrostructures symmetry, collective stability, order
Biochemistry Supramolecules interaction, functional integration, coordination
Molecular Biology DNA complementarity, epistasis, heterosis
Developmental Biology Homeotic genes organization, coordination, cooperation
Neurobiology Neuronal Transmission cooperativity, threshold effects, emergence
Ecology and Behavioral Biology Coevolution interactions, mutualism, parasitism
Symbiosis mutualism, cooperation
Sociobiology mutualism, reciprocal altruism, emergence, cooperation, division of labor
Anthropology Cultural Evolution symbiosis, cooperation, division of labor
Quantum Coherence: Sometimes referred to as "Bose-Einstein condensation," quantum coherence involves situations in which a large number of particles participate collectively in a quantum state; there is a wave function that is unentangled with its environment and behaves as if it were a single particle (Frölich 1970, 1975). Large scale versions of quantum coherence can be observed in superconductivity and superfluidity. In any case, collective quantum effects are synergistic in nature.
Chaotic Phenomena: "Chaos" involves unpredictable but deterministic interactions among phenomena that may result in coherent, collective states of order or disorder that are synergistic. Laminar flow and turbulence in fluid dynamics are examples. The so-called "strange attractors" or "dynamical attractors" that are highlighted in chaos models represent states whose stability properties arise from the interactions among the variables (Crutchfield 1986; Ditto and Pecora 1993).
Self-Organized Criticality: A process in which large composite systems that are involved in dynamic interactions may self-evolve to a critical state in which any further change can result in a global transformation (Bak and Chen 1991). Avalanches are an example, and it has been discovered that such phenomena are the result of the global properties of the whole.
Phase Transitions: Physicist Herman Haken (1973, 1977, 1983) and various colleagues have spent more than 20 years developing a science of cooperative phenomena called "synergetics", the objective of which is the elucidation of a set of general principles of cooperativity and cooperative effects. Phase transitions, which involve a collective change of state (e.g., laser beams, water turning into ice crystals or to steam at various critical temperatures, or the loss of magnetism in iron crystals at 7740C.) have been among the many important areas of synergetic analyses.
Dissipative Structures: Ilya Prigogine (1978) and his co-workers have built upon Erwin Schödinger's idea that there is a class of systems in nature that can defy the Second Law of Thermodynamics by being "open", or energy-processing in nature. They feed on throughputs of energy to sustain order, or "negative entropy," and can thereby remain in a sustained state of thermodynamic disequilibrium. Dissipative structures, according to Prigogine, may also be self-organizing. They may arise spontaneously and then spontaneously evolve toward greater complexity. This may occur when an open system is driven so far from an equilibrium condition that non-linear discontinuities, or threshold instabilities may occur that will transform the system in the direction of greater complexity and more structural stability. In any event, the behavior of dissipative structures, and the transitions between system states, are holistic phenomena; they involve cooperative effects. Indeed, an often overlooked point about thermodynamic processes is that "negative entropy", or a highly ordered energy state, also entails synergy -- a concentration of energy such that it is capable, collectively, of doing work.
Hypercycles: A major hypothesis about prebiotic evolution, the hypercycle model envisions a cyclical, mutually-reinforcing catalytic process among interrelated RNA-like precursors. As Manfred Eigen and Peter Schuster (1977, 1979) note, the build-up of functionally-proficient translation machinery in evolution required the integration of several different replicative components. This integration, they maintain, could only be achieved by a "mechanism" such as a hypercycle, which they characterize as a "cooperative" process. (Stuart Kauffman, 1993, has proposed an alternative model based on the idea of a collective phase transition involving connected sequences of biochemical transformations. He likens the process to one in which a set of pegs distributed on a floor are gradually connected by strings until, in due course, they reach a critical point where they combine to form a net -- a synergistic effect. Indeed, Kauffman characterizes the origins of life as an "emergent property" of complex systems of polymer catalysts; life, he says, has an "innate holism.")
Molecular Macrostructures: The macro-level material world exhibits many kinds of synergy. Indeed, Mendeleev's periodic table is a monument to the extraordinarily diverse ways in which the basic building-blocks of nature can be combined to produce emergent new phenomena with a great variety of synergistic physical properties and effects. Likewise, the multifarious chemical compounds that are found in nature (or synthesized in our laboratories and factories) are products of the covalent, ionic and coordinate bonds that "glue" atoms together. Some are so commonplace that we take them for granted: water, table salt, ammonia. Others are more exotic. Buckminster Fullerenes (Carbon 60 and several variants) provide a particularly apt example, because these recently synthesized molecules of pure carbon are named for the well-known engineer who invented geodesic domes (and incidentally promoted the concept of synergy). Nicknamed the "Bucky Ball," C60 was given its moniker because it derives its extraordinary stability from its physical resemblance to a geodesic dome, or a soccer ball. And it is the geometry of the whole that gives the Bucky Ball its distinctive collective properties (Curl and Smalley 1988).
Supramolecular Chemistry: The chemistry of molecular assemblies and intermolecular interactions is a fast-developing, interdisciplinary enterprise. It is focussed on the processes by which substrates bind to enzymes, how drugs find their targets, how coordinated actions occur among molecular assemblies, how signals propagate between cells, etc. Among the remarkable features of this research domain is the fact that "information" plays a key role, both in the processes of polymolecular self-assembly and in the intermolecular interactions, with results that are systemic in nature (Lehn 1993).
DNA: In the age of biotechnology and recombinant DNA, the renowned three-letter acronym for deoxyribonucleic acid is a household word. Most school children now learn about the double helix and the four nucleotide "letters" which make up the genetic "code." What is often glossed over is the fact that the properties of DNA are highly cooperative in nature. There is, first of all, the double-stranded, antiparallel "backbone" in which phosphate groups alternate with a sugar, deoxyribose, to form covalently linked chains, a structure which hangs together because its atoms share pairs of electrons. Also, the four nucleotide "bases" -- each a complex synthesis of carbon, nitrogen, hydrogen, and (except for adenine) oxygen -- can only perform their vital informational function because of their very specific complementarities: Adenine only pairs with thymine and guanine with cytosine. And it is the order in which the bases are arrayed in various three-letter "codons" (like the words in Table I above) that gives DNA its capacity for constructing amino acids. Furthermore, the functional capabilities of DNA depend on the highly coordinated transcriptional role played by three distinct forms of RNA (a division of labor), as noted above. Finally, the construction of a living organism requires a complex, multi-layered fabrication process. An estimated 2.5 billion base pairs are required to define the 50-100,000 genes in the human genome. (Even a simple virus like the much-studied SV40 in monkeys has 5,243 base pairs and five genes.) The genes function cooperatively to construct the 20 different amino acids which, in turn, are used to build several thousand different proteins. And, if there is even a single alteration in the gene sequence that codes for, say, hemoglobin, the result may be sickle-cell anemia, or worse.
*The Homeobox: It has long been appreciated that genes generally do not act alone in producing the phenotypes of the next generation. Many years ago, the geneticist Theodosius Dobzhansky (1937) demonstrated that, even in Drosophila (fruit flies), factors on all of the chromosomes (Drosophila have four) may contribute even to a simple trait like the size of the testes, and many experiments since then have confirmed the cooperative nature of the genome's functional organization. A particularly dramatic example is the homeobox domain, which was discovered in the 1980s (Gehring 1985; Maynard Smith and Szathmáry 1995). The homeobox refers a distinctive DNA segment, consisting of some 60 amino acids, that are found in all of the so-called homeotic genes and, remarkably, have been conserved over many millions of years of evolution in organisms ranging from fruit flies to humans. (There are about 10 homeobox segments in Drosophila and at least 40 in humans, arranged in four complexes on different chromosomes.) The homeotic genes apparently utilize the homeobox complex to determine the basic body plan of a given organism and serve as key regulators of embryonic development; they establish the body's architecture and tell the developing embryo what kinds of structures to make in each location. It is, in effect, a microscopic example of a combination of labor that is oriented to the production of a combined, emergent result (De Robertis, et al., 1990). More recently, the human genome mapping projects have greatly expanded our appreciation for the synergies that are involved in morphogenesis. The process of constructing a human brain, for instance, involves some 3,195 distinctive genes, the precise functions of which are rapidly being decoded (Goodfellow 1995; Little 1995).
Neuronal transmission: The human brain and nervous system is characterized by a complex and as yet only partially understood division (and synthesis) of labor among numerous functionally specialized areas/regions that are interconnected by an estimated 100 billion neurons. Many aspects of the brain's modus operandi (particularly the "binding" process by which the activities of the various parts are integrated into the "whole" that constitutes our conscious experience) still elude us. However, what we do know affirms that the workings of the brain are synergistic. We know that the neurons are in constant communication with one another via a network of staggering complexity. An individual neuron may have anywhere from 500 to 20,000 synaptic connections with other neurons, and at any given moment millions of neurons are firing in concert in a highly cooperative process. Even the transmission of a signal (an electro-chemical impulse) by a single neuron turns out to be synergistic. In brief, the "firing" process involves what Francis Crick (1994), characterizes as a "complex dynamic sum" of both excitatory and inhibitory inputs from all of the other neurons with which the neuron is in contact via the "synapses" (or junctions) between its own dendrites and the axonal endings, or "knobs" of neighboring neurons. The way in which signals bridge the synaptic cleft, the gap between neuronal junctions, is also highly cooperative. Even the mechanics of the transmission process within each neuron is, in Crick's words, a "chemical miracle." It is not at all like electricity flowing through a wire but an intricate process of chemical (ionic) balance shifts in electrical potentials, a dynamic which is facilitated by an elaborate system of molecular "gates" and metabolic "pumps." As Crick concludes: "A neuron, then, is tantalizingly simple...It is only when we try to figure out exactly how it responds...that we are overwhelmed by the inherent complexity of its behavior...All this shows, if nothing else, that we cannot just consider one neuron at a time. It is the combined effect of many neurons that we have to consider" (1994:103-104).
Coevolution: A term coined by biologists Paul Ehrlich and Peter Raven (1964) and subsequently developed by a number of other biologists (Thompson 1982; Futuyma and Slatkin 1983; Nitecki 1983), coevolution refers to the aspect of the evolutionary process that is driven by the interactions among species. Some are mutually beneficial; some are commensalistic (with benefits to one or more species without apparent detriment to others); and some are competitive, parasitic or predatory. Broadly defined, coevolution could encompass a major part of the total evolutionary process. But the consensus seems to be that the term should only be applied to situations in which one species becomes a "selection pressure" for another species in such a way that it precipitates step-wise directional changes over a number of generations in two (or more) species via reciprocal causation -- a sort of "arms race" or, conversely, a process of progressive accommodation and mutual facilitation. The paradigm-defining example, provided by Ehrlich and Raven, is butterflies and the plants on which they feed. Over the course of time, many plants have evolved chemical compounds that are apparently without physiological functions (alkaloids, quinones, glycosides, flavonoids, etc.,), yet they seem to be repugnant to otherwise predatory butterflies. The butterflies, in turn, appear to have diversified their diets (and their habitats) and to have evolved appropriate new digestive and concealment adaptations. In more extreme cases, coevolution may resemble what biologist Leigh Van Valen characterized as a Red Queen's race (from Lewis Carroll's Through the Looking Glass), where interacting species must run as fast as they can just to stay in place (see also Vermeij 1987). But, in any case, coevolutionary processes are relational and synergistic.
Symbiosis: The term "symbiosis" is generally used by biologists to connote the "living together" of "dissimilar" organisms -- sometimes for their mutual benefit and sometimes not. The classic example of a mutualistic symbiosis is lichen, a generic label for the roughly 20,000 different species of partnerships between some 300 genera of fungi and various species of cyanobacteria and green algae. Although many lichen partners can apparently live independently, in combination they enjoy significant functional advantages (synergies). (Empirical support can be found in a recent quantitative analysis by Raven, 1992.) Fungi have gripping and water-retention capabilities that can be especially advantageous in a relatively harsh or barren environment, while the cyanobacteria and green algae bring photosynthesizing capabilities to the partnership. The symbionts also commonly combine forces to produce a thallus. Some lichen even reproduce together (asexually) via symbiotic diaspores. Although symbiosis is often equated with mutualism, it also includes many examples of parasitism -- relationships which may or may not be deleterious (negative synergy) for one of the partners, including many cases in which the functional consequences vary with the circumstances. For example, the so-called VAM (vesicular-arbuscular mycorrhizal) fungi that are models of mutualism with many species of plants do in fact enhance plant growth in low phosphorous soils, but in high phosphorous soils or in low light conditions (when photosynthetic activity is reduced), they may become parasitic and reduce plant growth (Bethlenfalvay et al., 1983; Daft and El-Giahmi 1978). Ten years ago, symbiosis was still considered by many biologists to be a minor theme in evolution. However, a number of subsequent developments have elevated symbiosis to a place at the head table. Not only is the endosymbiotic origin of eukaryotic cells -- a major turning point in evolution -- now widely accepted, but there is a recognition that mutualistic and commensalistic associations (not to mention parasitism) are widespread throughout the living world. For instance, there is growing evidence of mutualism (as well as competition and parasitism) between many species of plants (Margulis 1993; Hunter and Aarssen 1988). Perhaps most remarkable, we are even discovering a vast new domain of mutualistic and parasitic interactions at the micro level, among bacteria, viruses, plasmids, etc., (Sonea and Panisset 1983; Weinberg 1985; Margulis 1993; Margulis and Sagan 1995; also, see below).
Sociobiology: As defined by Edward O. Wilson (1975), sociobiology is concerned with behavioral relationships among members of the same species, ranging from parent-offspring interactions to elephant seal "harems" and the tightly integrated division of labor in a number of social insect species. One of the most impressive examples of the latter is Eciton burchelli, a species of army ants found in Central and South America. E. Burchelli form highly organized colonies of about 500,000 members, with four morphologically distinct castes (in addition to the queen) that divide up the responsibilities for colony defense, foraging, transport, nest-making, and care of the brood. The so-called "submajors" (or porters), for instance, team up to carry sometimes very large prey which, if split up into pieces, would be more than each individual ant could carry alone. E. Burchelli's highly cooordinated foraging system is legendary. In a single day, a raiding party of up to 200,000 individuals, marching in a dense phalanx, may cover as much as 200 meters and reap some 30,000 prey items, many of which must be transported back to the nest. (Army ants are actually top carnivores; so far as is known, nobody preys on them, so formidable are their combined defensive capabilities.) One of the most remarkable features of E. Burchelli's adaptive strategy is the fact that the workers form nests out of their own interlinked bodies and are able to maintain an internal nest temperature within ± 10C. Moreover, during their 15-day nomadic periods, the colony moves its nest daily (to provide sufficient food for its growing brood), a process which involves a highly complex, coordinated maneuver. As ecologist Nigel Franks notes, army ant colonies also display flexible, problem-solving behaviors as an emergent property of the colony; their actions are not centrally-controlled (Franks 1989, 1991).
Cultural Evolution: The Igorot provide an example of how even a "primitive" human economy may depend on an intricate network of ecological, technological, social and political components. When they were studied in the 1970s by anthropologist Charles B. Drucker (1978), the Igorot occupied a mountainous area of Luzon, in the Philippine Islands, where for centuries they had practiced irrigated rice cultivation within an awe-inspiring system of earthwork terraces, dams and canals that were laboriously carved with simple tools out of the precipitous mountainsides. One key to the Igorot's subsistence mode was the remarkable, sustained fecundity achieved by the constant replenishment of soil nutrients, especially nitrogen. This depended on the presence in the rice ponds of nitrogen-fixing cyanobacteria that maintained a symbiotic relationship with the rice plants. Thus, over a period of several centuries, the Igorot were able to grow almost enough staple food on a single hectare to feed a family of five. Yet this is only part of the story. The Igorot's cultural adaptation also depended on a cooperative set of social arrangements. Whereas the ancestral Igorot had lived in small family groups and practiced a form of shifting, small-scale (slash-and-burn) plant cultivation, the successful adoption of the rice terrace mode of production required the coalescence of an integrated social organization. Sustained cooperative efforts became necessary, first to build the rice-terrace system and then to utilize, maintain and expand it over time, for without constant weeding and repairs the system would soon deteriorate. In effect, the productivity of each individual family plot depended on the productivity of the "whole". Accordingly, the Igorot had to invent a set of social and political structures and processes (and cultural norms) to coordinate in a disciplined manner the activities of the many previously isolated family groups. (A more recent study of the Balinese water temple system and its relationship to ecological and subsistence patterns, utilizing a dynamical systems model too complex to detail here, suggests the possibility that cultural practices with emergent, collective effects may also arise from self-organizing processes (Lansing and Kremer 1993).
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SOME IMPLICATIONS
As the sampler above suggests, a broad definition of synergy as cooperative, or combined effects of all kinds casts a very wide net over the phenomenal world. Indeed, synergy travels under many different aliases. Among other things, it encompasses emergent phenomena, functional and structural complementarities, the division of labor, threshold effects, phase transitions, symbioses, symmetries, coevolution, heterosis, interactions, cooperation, epistasis, systemic effects, even "dynamical attractors." Can such a broad definition be useful? We believe the answer is emphatically yes. Cooperative interactions are everywhere in nature, to be sure, but the particular focus of a synergy orientation is the subset of all imaginable interactions that have combined functional effects (positive or negative) for those aspects of the material world that we wish to understand more fully. Synergy shifts our theoretical focus from mechanisms, objects or discrete bounded entities to the relationships among things, and, more important, to the functional effects that these relationships produce. Synergistic causation is configurational; synergistic effects are always co-determined.
A point that was made earlier should also be stressed at this point. Synergy is real. Its effects are measurable or quantifiable: e.g., economies of scale, increased efficiencies, reduced costs, higher yields, lower mortality rates, a larger number of viable offspring, etc. More subtle measuring rods include enhanced stability properties, greater stress tolerance, increased fidelity in reproduction, the melding of functional complementarities to achieve new properties, and so forth. A frequently-invoked example of nutritional synergy can perhaps be used to illustrate: One-half cup of beans provides the nutritional equivalent (in terms of usable protein) of two ounces of steak, while three cups of whole wheat flour provide the equivalent of five ounces of steak. Eaten at separate times, the two food items contribute the equivalent of seven ounces of steak. But because of the complementarity of their amino acids, if the two substances are consumed together they provide the equivalent of nine ounces of steak, or 33 percent more useable protein. Here is a case where, literally, the whole is greater than the sum of its parts.
Another illustration can be derived from rowing, a sport which seems to be popular with biologists. In his near-legendary book The Selfish Gene, Richard Dawkins (1989/1976) concedes that genes are not really free and independent agents. "They collaborate and interact in inextricably complex ways...Building a leg is a multi-gene cooperative enterprise" (p.37). To underscore the point, Dawkins employs a rowing metaphor. "One oarsman on his own cannot win the Oxford and Cambridge boat race. He needs eight colleagues...Rowing the boat is a cooperative venture" (p.38). Furthermore, Dawkins notes: "One of the qualities of a good oarsman is teamwork, the ability to fit in and cooperate with the rest of a crew" (p.39). (The obvious inconsistencies between these statements by Dawkins and his ruling selfish gene metaphor are treated at length in Corning 1996, 1997.) In a similar vein, Maynard Smith and Szathmáry (1995) use as a metaphor specifically for synergy the image of two men in a rowboat, each with one oar. If only one oarsman is rowing, the boat will go in circles.
We can add a quantitative example to these nautical metaphors: A world class "varsity eight" (plus coxswain) can cover 2000 meters over the water in about 5.5 minutes. However, a single sculler can at best row the same distance in about 7 minutes. The difference is synergy, and if rowing faster were a matter of survival (and it may very well have been at various times in our history as a species), the cooperators would be the fittest. 2
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TOWARD A SYNERGY PARADIGM IN THE SCIENCES
Many years ago, the chemist Michael Polanyi (1968) proposed a definitive resolution to the long-standing debate over reductionist versus holistic approaches to scientific explanation. The natural world consists of a hierarchy of "levels," Polanyi wrote in "Life's Irreducible Structure," which can be identified empirically in relation to distinct "boundary conditions" that impose more or less inclusive constraints on the laws of nature. Each level works under principles that are irreducible to the principles governing "lower levels." Thus, the "laws" governing the properties of DNA are not reducible to the laws of physics and chemistry. Nor are the principles governing morphogenesis reducible to those that govern nucleic acids. Equally important, the principles that control higher levels may serve to restrict, order and "harness" lower levels. To use one of Polanyi's examples, the grammatical rules that govern the structure of various human languages utilize but also subsume the principles of phonetics. Accordingly, any hierarchically-organized phenomenon may embody several distinct sets of level-specific principles.
In another classic article entitled "More is Different," physicist Philip Anderson (1972) subsequently reinforced and expanded on Polanyi's argument. "The reductionist hypothesis does not by any means imply a ‘constructionist' one: The ability to reduce everything to simple fundamental laws does not imply the ability to start from those laws and reconstruct the universe...The constructionist hypothesis breaks down when confronted with the twin difficulties of scale and complexity...At each level of complexity entirely new properties appear... Psychology is not applied biology, nor is biology applied chemistry." Anderson used the now familiar term "broken symmetry" to characterize such qualitative shifts. Examples cited by Anderson included complex organic molecules, superconductivity and crystal lattices. "We can see how the whole becomes not merely more but very different from the sum of its parts," Anderson concluded. (Needless to say, these arguments have been reiterated many times since the early 1970s.)
While these two landmark articles helped to legitimize the development of such umbrella disciplines as theoretical ecology, hierarchy theory, chaos theory, dynamical systems theory and complexity theory, neither one squarely addressed the question: what precisely are the relationships between levels (and disciplines)? What are the causal factors in the phenomenal world that are responsible for producing the phase transitions and dynamical attractors that are simulated in our mathematical models? In other words, what are the functional relationships between parts and wholes? The frequent use by scientists of such descriptive terms as "emergence," "interdependency," "interactions," "positive cooperativity," "co-determination," and even "synergy" represent at least a tacit acknowledgment that the various levels of organization in nature are connected to one another. The term "emergence" is especially popular among die-hard reductionists, because it implies that wholes are merely the epiphenomenal effects of laws and causal processes that can be fully illuminated at lower levels. What is less frequently acknowledged -- and sometimes even denied -- is the fact that various levels may be interdependent; wholes and parts may interact, and coevolve, in complex ways. Indeed, the very concept of hierarchical "levels" may sometimes become an obstacle to understanding. (For more extended discussions of these points, see Wimsatt 1974; Kline 1995).
A synergy perspective suggests a paradigm that explicitly focusses on both wholes and parts, and on the interactions that occur among the parts, between parts and wholes and between wholes at various "levels" of interaction and causation. It might be called "a science of relationships," as distinct from a science of "mechanisms" or "laws". Thus, the phenomenon of consciousness may well be an emergent/synergistic product of a vastly complex set of interactions within the machinery of the brain and between the brain and the environment. However, as the late psychobiologist Roger Sperry argued repeatedly (eg., 1969, 1991), "downward" causation is also important in evolutionary processes (see also Campbell 1974). Synergistic wholes are also units of causation in the phenomenal world -- and in evolutionary change. Sperry was fond of using the metaphor of a wheel rolling downhill; all of its spokes, and its atoms and molecules, are bound to go along for the ride.
Of course, the relationship between parts and wholes is often more complicated than that. Parts may constrain the wholes in various ways. The mobility of a particular animal species, for instance, is strictly limited by the capabilites of its locomotive machinery, which in turn has been shaped by a complex nexus of influences ranging from the principles of physics and thermodynamics to the particular evolutionary history of its lineage. An organism's parts may also establish functional priorities for the whole (eg., its pressing survival and reproductive needs). Conversely, "higher levels" in the biological hierarchy may set priorities for lower levels. Thus, social insects, we now appreciate, respond in complex ways to the cues and signals that arise in their social environments -- at the "superorganism" level of organization (in Herbert Spencer's original formulation) and even beyond. (Indeed, many of these higher-level cues may be combined properties of the whole.) Thus, while the proximate mechanisms of behavioral control in social insects may be distributed, the organizational and functional principles are nevertheless superordinate and holistic.
In short, there is both upward and downward causation in nature, and very often a synthesis of the two. Moreover, wholes of various kinds may become interdependent "units" of selection and evolution, just as, conversely, the evolution of various parts may be shaped by the functional requisites of the whole. An example of the latter are the army ant submajors referred to above; their large size and long legs are morphological adaptations that reflect their role in the E. Burchelli division of labor. In like manner, symbionts (say mitochondria and their primitive protist hosts) may coevolve adaptations that serve the functional needs of the partnership as an emergent "unit" of selection (an obvious example is the synchronization of reproductive efforts).
Accordingly, a "synergy paradigm" implies a multi-leveled, interactional research focus, one which gives equal weight to both reductionist and holistic perspectives and invites both intra and inter-level analyses and explanatory models. (A number of philosophers of science have discoursed on this issue in recent years. In particular, see Wimsatt 1974, and Bechtel 1986.) One implication is that increased collaboration among the traditionally autonomous and often competing disciplines may be imperative for longer term scientific progress.
Water, perhaps the most studied of all substances, provides an illustration from the physical sciences. Despite our considerable knowledge of the remarkable substance which covers 70 percent of the earth's surface and which comprises about 65 percent of our bodies by weight, there are still properties and aspects of its behavior that we do not understand. The basic atomic properties of water have been understood for almost two centuries, thanks to John Dalton. We also know a great deal about the chemistry, statics, dynamics and thermodynamics of water, which is subject to numerous macro-level physical principles (as Polanyi pointed out). We understand, for instance, how the constituent atoms of hydrogen and oxygen are linked together by their covalent bonds. We know that quantum theory is required to explain some of the remarkable energetic properties of water. Additional principles of chemistry are needed to account for the state changes that produce water from its constituent gases and, under appropriate conditions, the changes that can reverse the process. Still other principles are required to account for the macroscopic properties of water as a liquid medium: its compressibility, surface tension, cohesion, adhesion, and capillarity. Thermodynamic principles are needed to understand the dynamics of temperature changes in water. Static principles relating to density and specific gravity must be invoked to account for the buoyancy of rowboats and varsity eights. Hydraulics are needed to understand how water reacts to a force exerted upon it. Dynamics, and Newton's laws, are relevant for understanding the tidal action of water in large bodies, while hydrodynamics is required to explain the behavior of water flowing through a pipe, or in a river bed. Here Bernoulli's principle also becomes relevant.
And yet, despite all of this knowledge, we still do not know exactly how water molecules "network" with other water molecules -- a key to understanding how water can be so fluid and yet have such an anomalously large capacity for absorbing heat and holding other substances in suspension (Amato 1992). Significantly, progress in studying various kinds of intermolecular interactions in water is being made via interdisciplinary efforts. In a recent report on molecular clusters in water, Colson and Dunning (1994) conclude: "This work also illustrates the synergism that has developed between experimental and theoretical studies in modern chemical physics."
By the same token, at the most inclusive geophysical level, the problem of understanding the role of water in world climate patterns presents a formidable research challenge that has necessitated multi-leveled, multi-disciplinary modelling efforts. Larry Goldberg (1994), a philosopher of science, has studied this research domain intensively. The complexity of the problem arises from the interdependence of various component subsystems -- the atmosphere (troposphere and stratosphere), the oceans and other large water bodies, the so-called cryosphere (continental ice sheets), the lithosphere (the earth's crust and upper mantle) and the biosphere (the activities of the earth's biota). Each of these "subsystems", which cut across the subject matter of at least half a dozen different disciplines, presents a complex set of modelling problems in its own right. Yet they also interact in different ways depending on the particular spatial location and time-frame. Consider, for example, the impacts on the oceans from fluctuations in solar output over various scales: days (r-Mode oscillations), years (quasi-biennial oscillations), tens of years (11- and 22-year solar magnetic cycles) and hundreds of years (Maunder-minimum type cycles), not to mention such regularities as the time of day and seasonal cycles, and variables such as cloud cover and cloud density. Thus, as Goldberg notes, at any given location, date and time of day, the level of solar radiation being absorbed by the oceans depends upon an extraordinarily complex set of interacting (synergistic) causal factors. These synergies demand multi-disciplinary analyses.3
Similar multi-disciplinary challenges confront the life sciences. A particularly striking example at the micro level is a recent study reported by Wang and his co-workers (1993) showing that the movement, shape and polarity of individual cells in a multi-cellular cluster depends on close cooperation among proteins outside the cell in the extracellular matrix (ECM), proteins that are found on the surface of the cell (cell adhesion molecules, or integrins) and proteins inside the cell (the cytoskeleton). Not only are there close interconnections between these system "components" but they are organized according to the so-called "tensegrity" (or tensional integrity) architecture that underlies Buckminster Fuller's geodesic domes. Furthermore, this parts/whole/environment interaction has been illuminated by the melding of two separate disciplines -- cyto-mechanics and detailed biochemistry (Heidemann 1993).
The same sort of challenge applies to the macro-biotic level, where there have been various efforts by theoretical ecologists in recent years to address parts-wholes interactions and the complex feedbacks that exist among various ecosystem "levels". Particularly notable is the hierarchical network approach developed by ecologist Claudia Pahl-Wostl (1993, 1995), which utilizes information theory and patterns of interlevel feedbacks in an effort to capture the spatiotemporal dynamics of an ecosystem. Pahl-Wostl (1993) concludes: "These order parameters arise from the interactions among the components of the systems through processes of self-organization. Along this line of reasoning the dichotomy between top-down and bottom-up control converges to a mutual and inseparable dependence on both factors. Neither a purely reductionist approach nor a merely holistic perspective is sufficient to encompass the intrinsic nature of the system's behavior."
A further implication of the "synergy paradigm" is that the phenomenon of synergy is more than simply the end-point, or outcome of the processes that drive the phenomenal world. Synergy is also an important source of causation in the ongoing evolutionary process. Indeed, a synergy focus directs our attention to one of the major wellsprings of creativity in evolution. The novelist and polymath Arthur Koestler observed that "true novelty occurs when things are put together for the first time that had been separate" (Koestler and Smythies 1969). A number of examples were cited above: the emergent properties of chemical compounds; the mitochondria that provide eukaryotic cells with specialized metabolic capabilities; the functional complementarity of the lichen partnerships; the exotic compounds that comprise super alloys and composite materials. 4
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THE SYNERGISM HYPOTHESIS
In The Synergism Hypothesis (Corning 1983), it was proposed that synergistic phenomena of various kinds have played a key causal role in the evolution of cooperation generally and the evolution of complex systems in particular; it was argued that a common functional principle has been associated with the various steps in this important directional trend. The reasoning behind this hypothesis can be briefly summarized.
First, it is necessary to return to the problem of defining natural selection -- a much-debated subject and an issue that may seem tiresome to those who are already familiar with the debate. And yet, misunderstandings persist. Evolutionists often speak metaphorically about natural selection (as did Darwin himself) as if it were an active selecting agency, or mechanism. Thus, George Gaylord Simpson (1967:219) asserted that "The mechanism of adaptation is natural selection....[It] usually operates in favor of maintained or increased adaptation to a given way of life." Similarly, Ernst Mayr (1976:365) informed us that "Natural selection does its best to favor the production of programs guaranteeing behavior that increases fitness." In his discipline-defining volume Sociobiology (1975:67), E.O. Wilson assured us that "natural selection is the agent that molds virtually all of the characters of species." More recently, Wilson (1987) provided a more ecologically-oriented definition of natural selection as "all the events that cause differential survival and reproduction." Nor does it clarify matters when Dawkins (1989[1976]:v) characterizes living organisms as "robot vehicles blindly programmed to preserve the selfish molecules known as genes," which implies that genes are the locus of evolutionary causation. (See also the contribution by Endler in Keywords in Evolutionary Biology, 1992.)
The problem is that natural selection is not a mechanism. Natural selection does not do anything; nothing is ever actively "selected" (although sexual selection and artificial selection are special cases). Nor can the sources of causation be localized either within an organism or externally in its environment. In fact, the term natural selection identifies an aspect of an ongoing dynamic process. It is an umbrella concept that refers to whatever functionally-significant factors are responsible in a given context for causing differential survival and reproduction. Properly conceptualized, these "factors" are always interactional and relational; they are defined by both the organism(s) and their environment(s)..
This crucially important point can be illustrated with a textbook example of evolutionary change -- "industrial melanism." Until the Industrial Revolution, a "cryptic" (light-colored) species of the peppered moth (Biston betularia) predominated in the English countryside over a darker "melanic" form (Biston carbonaria). The wing coloration of B. betularia provided camouflage from avian predators as the moths rested on the trunks of lichen-encrusted trees, an advantage that was not shared by the darker form. But as soot blackened the tree trunks in areas near growing industrial cities, in due course the relative frequency of the two forms was reversed; the birds began to prey more heavily on the now more visible cryptic species (Kettlewell 1973).
The question is, where in this example was natural selection "located?" The short answer is that natural selection encompasses the entire configuration of factors that combined to influence differential survival and reproduction. In this case, an alteration in the relationship between the coloration of the trees and the wing pigmentation of the moths, as a consequence of industrial pollution, was an important proximate factor. But this factor was important only because of the inflexible resting behavior of the moths and the feeding habits and perceptual abilities of the birds. Had the moths been subject only to insect-eating bats that use "sonar" rather than a visual detection system to catch insects on the wing, the change in background coloration would not have been significant. Nor would it hav
Peter A. Corning, Ph.D.
Institute for the Study of Complex Systems
Email: pacorning@complexsystems.org
This post was modified on 24 Sep 2008 at 10:04 pm.- 24 Sep 2008, 9:42 pm
