Biology and Philosophy 14: 561–584, 1999. © 1999 Kluwer Academic Publishers. Printed in the Netherlands.

Evolutionary Change and Epistemology TREVOR HUSSEY Faculty of Applied Social Science and Humanities Buckinghamshire Chilterns University College Queen Alexandra Road High Wycombe Buckinghamshire HP11 2JZ UK

Abstract. This paper is concerned with the debate in evolutionary epistemology about the nature of the evolutionary process at work in the development of science: whether it is Darwinian or Lamarckian. It is claimed that if we are to make progress through the many arguments that have grown up around this issue, we must return to an examination of the concepts of change and evolution, and examine the basic kinds of mechanism capable of bringing evolution about. This examination results in two kinds of processes being identified, dubbed ‘direct’ and ‘indirect’, and these are claimed to exhaust all possibilities. These ideas are then applied to a selection of the debates within evolutionary epistemology. It is shown that while arguments about the pattern and rate of evolutionary change are necessarily inconclusive, those concerning the origin of novel variations and the mode of inheritance can be resolved by means of the distinctions made here. It is claimed that the process of selection in the evolution of science can also be clarified. The conclusion is that the main process producing the evolution of science is a direct or Lamarckian one although, if realism is correct, an indirect or Darwinian process plays a vital role. Key words: change, evolution, evolutionary epistemology, selection

1. Introduction This paper is an attempt to settle the dispute in evolutionary epistemology concerning the nature of the evolutionary process which brings about change in science and society. Put briefly, its primary concern is the debate between those who believe that the process is essentially the same as that which produces biological evolution, that is to say Darwinian, and those who hold it to be Lamarckian. Amongst recent contributions, Hull (1988) presents us with perhaps the most thorough exposition of the first thesis and Gould (1996) gives a brief but trenchant statement of the second; and they cannot both be right. However, in this tangle of issues, even the terminology is misleading,

562 and to resolve the dispute it will be necessary to return to an examination of the fundamental concepts of change and evolution, and the mechanisms that bring them about. There can be no doubt about the importance of the debate, since it concerns the nature of the processes that bring about evolutionary change in the world. In evolutionary epistemology it has become bound up with a complex knot of disputes. Amongst those who favour the Darwinian paradigm, some have argued that the claims of a Lamarckian component in sociocultural change rest on a distorted understanding of Lamarck’s ideas (Hull 1982, 1988). Others have accepted that some aspects are Lamarckian – or at least non-Darwinian – but have not seen this as vitally important (Popper 1975, 1979; Toulmin 1972; Campbell 1979), while their critics consider that this admission undermines the whole enterprise (Cohen 1973, 1974; Losee 1977). Here arguments about the role and significance of intentionality in scientific change, the rationality of science and the vexed subject of progress, become important because they have to be shown to be consistent with the favoured process of change. In turn, these debates raise the question of whether, in evolutionary epistemology, evolutionary theories are being applied literally, analogically or metaphorically. Several theorists have offered generalized versions of Darwinian theory (Popper 1975; Toulmin 1972; Hull 1988); a move which plunges us into the problems surrounding the nature of the ‘evolutionary units’ involved. In biology the most widely held (but controversial) view has been that species evolve, organisms are selected and variations are provided by gene mutation, but evolutionary epistemologists have debated a wide variety of candidates as analogues to these units. The most promising way to sort out this multiplication of entities is to see evolution as involving lineages of ‘replicators’ housed in ‘vehicles’ or ‘interactors’, interacting with each other and the wider environment (Dawkins 1976, 1978; Hull 1981, 1982, 1988). However, although these ideas may be important, it remains to be shown that they apply in the sphere of sociocultural evolution and that the process at work is Darwinian. This sketch of the tangle of issues suggests that, if they are to be resolved, we need to stand back from the imbroglio and examine the fundamental concepts of change in general and evolutionary change, followed by an investigation of the kinds of process or mechanism that can produce them. When this is done, a complex picture emerges which shows that a Darwinian process has brought into being a system capable of evolving by a different, essentially Lamarckian, means; but that this, in turn, is circumscribed by a broader Darwinian process.

563 2. Change and evolution Philosophical accounts of change have generally followed Aristotle in considering that the paradigm is a physical object changing over time. Change is said to involve an object which persists and retains its identity through time, while possessing (or lacking) a certain property at one time and lacking (or possessing) that property at a later time. The narrowness of these analyses contrasts with the rich variety of our talk of changes: whether everyday, scientific or philosophical. We speak of changes in things that are difficult to recognise as ‘objects’, such as species, minds, theories, beliefs, concepts, stories, arguments, affections, and fashions; and some of these are central to discussions of evolutionary epistemology. We also talk of changes in dimensions other than time: as when we say that a wall changes in height along its length or atmospheric pressure changes with altitude. These usages are often dismissed as mere figures of speech (McTaggart 1927; Geach 1972; Lombard 1986), but when discussing evolution – and especially evolutionary epistemology – we need a completely general criterion of change. The task of devising such a criterion is a formidable one (Hussey 1994), and here it will only be possible to offer a summary account. We can begin by observing that our concept of ‘change’ is related to our concept of ‘difference’. All changes involve differences but not all differences involve change. A kitten may change into a cat and the latter is different from the former, but two cats may differ without change being involved. Change involves a subject that persists throughout, while difference does not. The differences involved in any given change must be differences in properties, parts or states that can be properly predicated of the persisting subject of the change.1 Change takes place along a dimension. We most naturally think of this as being time, and this is the dimension involved in discussions of evolutionary epistemology. But, as already mentioned, a completely general account must allow for change along other dimensions, such as space. The subject of the change must have criteria of individuation and of reidentification, and it must be capable of persisting along the dimension of change. For example, a flagpole must be extended in time to be damaged or re-painted, but be extended in space to change in diameter with height. Given these components we can develop a general criterion giving the necessary and sufficient conditions for something to be a change (Hussey 1994). A succinct version, sufficiently precise for our purposes is as follows: There is a change if and only if there is a subject S which persists and retains its identity along a dimension from x1 to x2 , and there is a difference which is exhibited by a property, state or part properly predicated of S, from x1 to x2 .

564 This criterion specifies what something must be to be a change of any kind, but we are concerned here with evolutionary change – a species of extended change involving multiple differences, and distinguishable from others such as revolutionary, random and cyclical change. Since evolutionary epistemology is concerned with change over time, the following discussion will generally be confined to this form. Everyday and technical uses of ‘evolution’ and ‘evolutionary’ are rather disparate and do not lend themselves to precise definitions but, in general, evolutionary changes can be identified either by their characteristic form or by their mode of generation. In form they are extended changes showing continuity and involving a fairly smooth or orderly emergence of novelty. Any given segment is a modification of that which precedes it, without interruptions or sudden transitions. However ‘evolve’ stems from the Latin ‘evolvere’ meaning to unroll or roll out and, although this specific reference to unrolling is absent in most uses, in many a mode or process of generation is implied. ‘Evolution’ often refers to an unfolding, opening out or emerging of what is hidden or contained in some pre-existing compact form or plan: the development of what is potential or rudimentary. A military campaign or foetus might evolve in this sense. It may also be applied to a progressive or developmental change towards a goal or a more perfect state. The modern use of the word ‘evolution’ in biology does not fit either of these descriptions exactly, despite their breadth. In the Eighteenth Century it was used to refer to the development of an embryo and was intended, conventionally enough, to convey the gradual unfolding of pre-formed parts. Then, during the Nineteenth Century it came to be used to denote the transmutation of biological forms and hence the origin of new species. Under the influence of Darwin’s theory it was used to refer to the kind of gradual, adaptive change believed to result from natural selection, although some authorities, especially Herbert Spencer, retained the implication of progress in their use of the word. However, once established in this way, the term ‘evolution’ was retained even to cover non-gradualist theories of change such as saltationism and, more recently, that of punctuated equilibrium. Thus, in biology, ‘evolutionary’ may be used to refer to changes neither generated by a process of unrolling nor possessing some of the features generally attributed to evolutionary change. While the rise of novel forms remains important there is no longer a requirement that evolutionary change must be continuous and gradual in its form, although some theories maintain that, as a matter of fact, it is. Being a species of change, evolution requires a subject: something that preserves its identity through the change and which possess properties or parts which show differences along the dimension of change. The subject may be simple or composite and its identity can be retained by appropriate means,

565 such as spatio-temporal continuity, the ancestor/descendent relationship, and so on. It may be worth observing that statements and expressions such as ‘X has evolved’ or ‘the evolution of X’ are ambiguous. X may be either the product or the subject of the evolution in question. A particular model of Jaguar sports car is the product of an evolution, of which the series consisting of Jaguar sports cars, together with the related designs and specifications, is the subject. The debates concerning organic evolution are too extensive to explore here, but it will be accepted for our present purposes that the units of selection are products, while the subject of the change – that which can properly be said to undergo evolutionary change – is a form of lineage (Hull 1988; Hussey 1994). If it is claimed that evolution is taking place, whether biological, scientific or cultural, it will be necessary to specify a subject of that change and specify which of its properties, states or parts are exhibiting differences or ‘variations’ of the appropriate kinds.

3. Mechanisms of evolutionary change By its nature, evolutionary change stands in need of explanation, not merely of its initiation but also of the form it takes. Here, ‘explanation’ will be interpreted in a very broad and non-technical sense, to mean the offering of a plausible mechanism or process to account for the change. A complete explanation would have to account for the nature and persistence of the subject – for example, how each element in a lineage is generated from its predecessor(s) and information is passed on – how the differences or variations in its properties or parts are produced; and why the evolution takes the particular form that it does. Mechanisms in the physical world will offer causal explanations (at least at the macro-level), but in other areas – such as cultural change or epistemology – causation may be thought inappropriate. The detailed mechanisms that might be proposed are legion and may be classified in many ways, but the most important distinction is between those that work directly and those that work indirectly by means of selection. I suggest that these two categories embrace all possible mechanisms.2 A direct mechanism of evolution is one which acts on the subject of the change and determines which of its properties, states or parts will exhibit differences, what form the differences will take, when they will occur, with what frequency and in what order. No selection is involved except in the sense that, from amongst all of the possible variations or differences that could have occurred, a certain sequence did so and in such a way to constitute an evolutionary change. If this is to count as selection then it could be called ‘pre-selection’ since it occurs before the variations become actual.

566 It is tempting to think of direct mechanisms as simple causal chains – merely processes in which an external environment impresses itself on a passive, malleable substrate (Plotkin 1994) – but this is an inadequate picture. For example, the subject of the change might be a material object possessing colour, which is caused to darken over time in an evolutionary sequence of shades. Explanations might invoke such things as the unfolding of a plan intrinsic to the object; the following of a rule; a purposeful striving by the object; an external agent purposefully bringing about the change; an internal chemical process in the response to external stimuli and so on; but all would be direct mechanisms. Components of a direct mechanism may be in the subject itself or in the environment in which it exists, or both. The changes brought about by the process of photosynthesis (which may or may not have an evolutionary form) are due to a direct mechanism of great complexity. It is possible for a direct mechanism to bring about evolutionary change in a collection or population as well as an individual. Thus the movement of soldiers on a parade or the development of an embryo (consisting of a population of cells) are both evolutions which might be explained in this way. Organic evolution would be produced by a direct mechanism if it were purely orthogenetic or if minutely dictated by a god and, as we shall see in Section 4, Lamarck’s theory proposes a direct mechanism of evolution. Direct mechanisms of evolutionary change can be seen as a sub-set of those direct mechanisms that bring about variations in properties of any kind, whether random, haphazard, cyclical or any other way. Many changes brought about by direct mechanisms might be predictable in terms of our knowledge of the properties of the substances involved, causal laws and so on. However, as explanations of evolutionary, or other orderly change, they suffer the disadvantage that the very orderliness and continuity they are invoked to explain, remain in the nature of the mechanism itself. What I call indirect mechanisms of evolutionary change involve selection. From a population of existent and differing entities, containing more than the subsequent change will include, a sub-set is repeatedly selected so as to constitute the relevant evolution. For example, consider an array of objects which vary in the lightness-darkness values of their colours. If a series of selections were made in which the lightest objects were removed each time, this would produce an evolutionary change in the array. In this simple example all of the variation exists in the initial population, but in more complex examples new variations could be introduced as the selections proceed. Differences in the entities must occur randomly or at least in a way unconnected with the evolution in question and be selected in such a way as to produce the evolution.

567 Selection works on populations or collections of particulars – entities capable of being individuated – and which differ in such a way as to allow selection to occur. Minimally, it involves picking out and distinguishing some and not others, but it may also involve some kind of differential ‘treatment’ of the individuals. This selection may be called ‘post-selection’ because only some of all the actual variations in the entities come to constitute the evolutionary change. Since mere random elimination would not produce change of an evolutionary form, a description of a process of selection must include a statement of criteria according to which some properties or parts are being selected as opposed to others. Such criteria may themselves alter thus producing different patterns of change. For these reasons indirect evolutionary mechanisms are a sub-set of indirect mechanisms in general. Darwin’s theory of organic evolution can be seen as proposing an indirect mechanism. Notice that, as described, indirect mechanisms can be invoked only to explain the evolutionary form of the change, not the origin of the variations, and a full account will include an explanation of the latter. It is a necessary feature of indirect evolution that the form of the change is determined by the selective process and not by the variations alone; for this would be a direct mechanism. The differences or variations must be ‘blind’ in the sense that their nature and the timing of their occurrence are unconnected with the demands (or criteria) of the selective process. However, this does not exclude the possibility that what is involved in the selective mechanism is also responsible for producing the variations but, in general, indirect mechanisms need to be supplemented by a mechanism for producing variations before a full explanation of an evolutionary change is possible. In the biological world this will take the form of various mutagenic processes, and will be a form of direct mechanism, but not a direct mechanism of evolution, merely one of producing variations. It is obvious that direct and indirect mechanisms of evolution can interact in various ways, or work along side each other, to produce either a single evolutionary change, or several evolutionary changes simultaneously in the same subject. It is, at least, conceivable that sociocultural evolution is produced by various combinations of direct and indirect process. In any specific case it may be very difficult to discover which kind of mechanism is operating. When painting a picture an artist may act directly by deliberately creating a work according to a preconceived plan, or may produce a series of effects before selecting what seems most suitable: only close inspection can reveal the actual mechanisms involved.

568 4. Lamarckian and Darwinian theories Lamarck (1809 (trans. 1914), 1815–1822) tried to give an essentially naturalistic account of evolution in the biological world, without appealing to purposeful strivings or teleological explanations: contrary to the picture painted by his critics. He held that the organic world is not fundamentally different from the inorganic: indeed spontaneous generation and death ensure a constant cycle between the two. Living things consist of the same fundamental stuff as the rest of the physical world, but they posses different powers or capacities and it is these that make evolutionary change inevitable. Lamarck’s theory suggests two direct mechanisms. The first concerns the capacity life has to develop through an orderly sequence of forms from the simple to the complex or most “perfect”. The whole process is driven by what Lamarck called the ‘power of life’ and, over many generations, it produces a continuous spectrum of forms. The forms do not become extinct as they develop into the next, because the whole organic community is continually being replenished by spontaneous generation at the level of the simplest organisms, while mankind represents the most complex form yet developed. The ‘power of life’ is a non-teleological direct mechanism of evolution. Although the change it produces has a direction, there is no purpose or goalseeking implied. Lamarck held that the trend towards increasing complexity arises simply from the nature of living substance. The orderly succession of transformations no more implies a teleological explanation than does the evolution of a star from its initial condensation to its end as a white dwarf. However, it is clear that the ‘power of life’ has no explanatory power. Even if we were to agree that organic matter has a tendency to develop ever more complex forms, the ‘power of life’ tells us only that organic matter has the capacity to do so. What seems to be needed is a description of the properties and causal powers of living material which accounts for the developmental process. Lamarck does make an attempt to flesh out his ideas by invoking the operations of ‘subtle fluids’ and the phenomenon of ‘universal attraction’ which draws all particles of matter together. But, as well as being factually mistaken it is doubtful if these ideas are any more explanatory than the ‘power of life’. The second component of Lamarck’s theory offers a mechanism concerned with the influence of the environment on living organisms. The changing environment produces anomalies in what would otherwise be a more or less smooth continuum of development due to the ‘power of life’. A variation in the environmental conditions alters the needs of the affected organisms, and they respond by modifying their activities. If the environmental conditions persist long enough, the new activities become habits, and

569 these involve the increased use of some organs or bodily parts, and the disuse of others. In turn, increased use leads to the strengthening and enlargement of organs while disuse leads to atrophy. So far the mechanism has explained only the modification of individual organisms faced with a change in their environment. The final step explains how the whole species is transformed. Lamarck suggests that the modifications obtained by individuals during their lifetime can be passed on to their offspring: The notorious principle of the inheritance of acquired characters. There have been two main criticisms levelled at the second component of Lamarck’s theory. First, he has been accused of explaining evolution in terms of the wants or conscious strivings of individual organisms. It can be argued that this criticism stems from the ambiguity of Lamarck’s writing and the misinterpretations of his critics but, in any case, it is clear from the above account that it is possible to give an interpretation of his theory which avoids this objection. The second criticism focuses on the principle of the inheritance of acquired characters. There is now little doubt that this process of inheritance is wholly mistaken; as is Darwin’s similar theory of pangenesis. But two observations are warranted here. First, this criticism of Lamarck (and Darwin) shows only that as a matter of fact they are wrong. It does not show that the ideas are logically absurd. Second, the criticism only establishes that these processes of inheritance do not apply to organic evolution as it occurs on Earth. It gives us no reason to believe that they, or closely analogous processes could not operate elsewhere or in a different context, such as in the evolution of science or society. However, there is a much more fundamental criticism to be made of Lamarck’s second mechanism: it is unacceptable not because it offers a false explanation of organic evolution, but because it offers no explanation at all. In brief, the theory merely states that organisms respond in an adaptive way to environmental pressures but does not say how or why they do. An organism may need to respond to a change in its environment if it is to survive, but there is no logical or conceptual connection between an organism’s needs and its subsequent behaviour. In contrast, Darwinian theory can explain why, for example, animals tend to seek food when they lack it. Very roughly, those animals that happened to be disposed do so were more likely to survive and reproduce than those that were not; and if the disposition was determined genetically the trait proliferated. But Lamarck’s theory merely states that such a need will lead to the appropriate behaviour, without explaining why. A similar pattern of criticism applies to the other segments of his proposed mechanism: no explanation is given of why the persisting need establishes a habit or why use and disuse change the strength or size of organs. (Dawkins

570 (1986) makes a similar point about use and disuse.) Lamarck makes some attempt to describe the causal links that connect the various segments in his mechanism. For example, he suggests that the increased use of an organ involves a corresponding increase in flow of various fluids within it, which swells the channels and openings, thus enlarging the organ. But again this is merely to describe a possible mechanism: it does not explain why it is in place. However, it is important to notice what this criticism of Lamarck’s theory does and does not establish. It shows that if there is a direct mechanism by which environmental changes bring about adaptations in an organism, then its existence must ultimately be explained in Darwinian terms. It does not show that such adaptive mechanisms cannot exist. Indeed they obviously do so in abundance: muscles enlarge with use, fur thickens in cold weather, fair skin protects itself from prolonged sunshine by tanning, and so on. Of course, in the absence of a mechanism for the inheritance of acquired characters, these ‘adaptations’ are not themselves passed on to offspring and so they are not adaptations in the sense used in biological evolution; although the mechanisms that bring them about are. These points have significance for the discussion of evolutionary epistemology, the development of science and social change. It may be true that the human brain and its capacities are products of Darwinian evolution, but this does not mean that, in turn, its products must change by means of the same mechanisms. Darwin’s theory, expurgated of such ancillary hypotheses as pangenesis and the role of use and disuse, offers an indirect mechanism of evolutionary change. In brief, organic evolution proceeds by natural selection acting on heritable variations in phenotypes; the variations being ‘blind’ in the sense defined above. This is not the place to discuss the several versions of this theory or the controversies that surround them, but it is necessary to express it in a general form which lends itself to applications beyond organic evolution. A Darwinian indirect mechanism requires a population (a ‘world’) of interacting entities capable of being individuated and reidentified. These entities must possess properties, or parts which exhibit differences of the kinds defined earlier. A sub-population of these entities (the ‘units of selection’), equal to or less than the whole must be the subject of replication or copying, such that tokens are produced which are qualitatively similar to, but not necessarily qualitatively identical with, the specimens from which they were copied. The replication transmits the structure of one token to the next but an additional process may introduce novel variations. The proportion of similarity and difference between tokens may vary, and will affect significantly the kind of evolutionary change possible within the population, but the form that the evolution takes will be determined by the selective process.

571 Selection will be due to interactions between the members of the lineage and between them and the rest of the ‘world’: their environment. Selection will proceed by terminating lineages, the terminations being related to the variations exhibited by the tokens making up the lineages, in such a way that the probability of an entity generating, or contributing to the generation of, another entity depends on these features. In this way the features of those entities which stand at the termini of lineages and those that make up continuing lineages will depend in a systematic way upon the nature of the process of selection prevailing over the relevant periods. A description of the properties which lead to the continuation of a lineage are what I called the criteria of selection operating over that section of the dimension of change. For the change to have an evolutionary form the criteria of selection must prevail for a number of generations of the entities being selected. This description of a Darwinian mechanism is intended to be completely general. If we confine ourselves to temporal change, the lineages consisting of entities and the generative processes between them constitute the subjects of the evolution, and the entities or processes existing at any time slice are the products of the evolution. If it is claimed that a Darwinian mechanism is at work in any area, say the development of science, then it must be possible to identify the various components described. 5. Evolutionary epistemology Armed with these observations it is now possible to evaluate a selection of the arguments in evolutionary epistemology concerning the nature of the processes at work. The first two arguments, although interesting for other reasons, are doomed to be inconclusive about the nature of the evolutionary process. The following two, I believe, can be resolved and shown to establish that there are radical differences between the mechanisms operating in the organic and sociocultural spheres. A preliminary point has to be made before we begin: the existence of evolutionary change in science and culture is a necessary condition for the whole enterprise of evolutionary epistemology, so one important task is to scrutinise the putative examples from historians and sociologists to see if they possess the required features. However, for the purposes of this paper it will be assumed that there are examples of evolutionary change in the requisite spheres, and that it is possible to identify the various components described above: a continuous subject of change, features which exhibit differences and synchronic products of the evolution. Here we will be concerned with arguments about the process or mechanism of change, primarily in science. The workings of any such mechanism must be consistent with what scientists, philosophers, historians, and sociologists tell us about

572 the practises of science, and the mechanism must be capable of producing evolutionary changes with the forms and patterns they describe. To take up the last point first: some authorities (e.g. Popper 1979; Ruse 1986; Gould 1996) have remarked upon the difference between the pattern of biological evolution and that of science. In the organic world evolution is generally depicted as having the form of a tree which branches repeatedly so as to produce an increasing diversity of species curbed only by extinctions; while the fusing of branches is a fairly rare phenomenon brought about when hybridization produces fertile offspring. In contrast, the evolution of scientific theories is often portrayed as a process in which old theories are subsumed within new theories of ever greater generality. Thus the evolutionary tree of science is the biological tree inverted. Campbell (1979) makes a related point about the prevalence of cross-lineage borrowing of concepts in science, in contrast to the rarity of cross-lineage borrowing of genes in biological evolution. It can be argued that these differences cast doubt upon the thesis that the same, Darwinian, mechanism is operating in both fields. One response to this objection is to point out that the differences in pattern have been greatly exaggerated. For example, the formation of new species by hybridization is not uncommon amongst plants; and convergence by subsumption in science is rare outside the physical sciences and, since Kuhn (1970), controversial even there. Hull (1982, 1988) makes an analogous response to Campbell’s point about cross-lineage borrowing. The debate is complicated by the fact that much depends on which lineages one chooses as the subjects of evolutionary change. For example, in sexually reproducing species lineages of organisms merge at each mating whereas in asexual species they do not. However, I suggest that these responses are, at best, inconclusive. There is nothing in the above description of direct and indirect mechanisms that allows us to distinguish between them in terms of the pattern of change they produce. Furthermore, it is not unreasonable to expect a Darwinian process to produce different patterns of change when operating on very different substrates, and in which the components of the process are enormously varied. The evolution of, say, social groups may be unlike that of ideas or theories, and they will all be quite unlike the evolution of biological species whatever mechanism is operating. For example, Popper (1979, p. 263) points out that the evolutionary tree of ‘. . . human implements or applied knowledge’ is more like that of living organisms than that of theories. The higher rate of change in sociocultural evolution, compared to biological evolution, also suggests that different mechanisms may be at work. There are, of course, problems about measuring and interpreting rates of change (Hull 1988). In cultural evolution a number of authorities have begun

573 to develop models which go some way to providing quantitative measures and which can be applied to historical case studies (Cavalli-Sforza and Feldman 1981; Boyd and Richerson 1985) but it remains questionable whether we can make meaningful comparisons between change in radically different spheres. Nonetheless, Gould (1996, p. 220) is struck by the ‘explosive rapidity’ of cultural change and claims that it ‘. . . can vastly outstrip the maximal rate of natural Darwinian evolution’, and this is part of his argument in favour of a Lamarckian mechanism of cultural evolution. While I accept that this difference in rate of change appears real and that it may be of considerable importance in explaining serious tensions in human society, I do not think the argument shows conclusively that the mechanism is not a Darwinian one. Once again it seems reasonable to suspect that the same process may produce very different effects in different spheres, and that cultural evolution may be more rapid because of the nature of what is changing rather than because of a difference in the process involved. As with the previous argument, the most that we can conclude is that there are striking differences between the form that evolution takes in the social world, and that produced by the Darwinian process at work in biological world. I will now consider some arguments which are more directly concerned with the kind of mechanism producing evolutionary change in science, beginning with two closely related debates: one about the origin of the novel innovations required for evolutionary change, the other about the nature of the heredity involved. Here we shall see that the observations made in Sections 2, 3 and 4 are more decisive, and capable of cutting through the tangle of argument that has grown up around these issues. The first debate concerns the origin of the differences required to furnish evolutionary change. The point was made in Section 4 that indirect mechanisms, such as the Darwinian one, have to be supplemented by a direct process to produce sufficient novelty to allow evolutionary change, but which is not such as to constitute a direct mechanism of evolution and so render selection redundant. In the biological world the novel variations are mutations and recombinations of genetic material, while in science they are, variously, conjectures, novel ideas, novel memes, or according to Popper (1975, p. 82) the ‘. . . new and revolutionary tentative theories.’ But the way in which the innovations arise in the biological and scientific realms is vitally important. Many authors (e.g. Rescher 1977; Skagestad 1978; Thagard 1980) have claimed that, while genetic variations are ‘blind’ in the sense described above, innovations in culture – and especially science – are not. First, scientific innovations are usually prompted by the pressures of the hostile environment: new hypotheses or theories are generally produced because of critical attacks on current theories, experimental failure, or social and psychological

574 pressures within the profession. In general genes do not mutate more rapidly merely because the organisms carrying them come under increased selective pressure. Second, scientists usually introduce innovations that are purposely designed to overcome or avoid criticisms or experimental set-backs: the innovations are neither blind nor random. It is clear that this point introduces the formidable problems of determining the exact role of intentionality and teleological factors in the scientific enterprise, and hence understanding the purported rationality and progress of science. What matters here is that if innovations in science are not blind, then this appears to be a radical departure from the Darwinian model. Evolutionary epistemologists have reacted to this dilemma in various ways. Some, such as Popper in his later writing (1975, 1984), have recognised this disanalogy but argued that it does not invalidate the generally Darwinian approach to the evolution of science. Toulmin (1972) accepts that cultural evolution is not strictly neo-Darwinian, but persists in the view that both are related species of the same genus of populational explanations. However, Donald Campbell has offered the most radical response. In a series of papers (Campbell 1960, 1974, 1977) he has argued that the psychological process by which new ideas are produced corresponds closely to that which produces novelty in genetical inheritance. Once they emerge into the public arena of science, ideas may appear to be directed at solving particular problems, but the psychological process by which they were developed involves the generation of ‘blind’ novelties, which are then selected by the individuals involved. What is more, the selection processes themselves are the result of a prior Darwinian process of phylogenetic evolution. The latter point is, of course, irrelevant if the ‘selection processes’ referred to are genetically determined: as stressed earlier, the fact that our psychological capacities, and the neurological apparatus underlying them, have arisen by a process of Darwinian evolution does not mean that they must also function in that way. Similarly, even if it transpires that the ontogenetic development of our brain is a Darwinian process, as has been claimed (Edelman 1987; Plotkin 1994), this does not establish that our patterns of reasoning must themselves be Darwinian. However, the main part of Campbell’s thesis is less easily dismissed. The most obvious objections are, first, that it does not correspond to the process of discovery as experienced by practising scientists and, second, in any case, the number of possible novel ideas or conjectures is enormous, if not infinite; hence the chances of any problem being solved by selection from them, is negligible (Skagestad 1978). To counter the second objection, Richards (1987) has argued that the pool of possible conjectures is circumscribed by such things as psychological dispositions, the prevailing social milieu and

575 educational tradition and so forth. A similar line forms part of the attempt to preserve an essentially Darwinian model by Stein and Lipton (1989). They argue that there are two sources of new variations. One is ‘hidden chaos’: the random generation of innovations, a la Campbell, of which we see only those that survive. The other involves epistemic preadaptations, analogous to the biological preadaptations which help to account for the evolution of complex organs. These restrict the variety of likely innovations, a la Richards but, more importantly, include heuristics which guide the production of epistemic variations. Just as, for example, the ossicles of the mammalian middle ear arose by modifications of some of the hinge bones of the reptilian jaw, so new scientific theories arise by adapting those that already exist; the changes being guided by a host of readily available ‘discovery heuristics’. The latter include abstract rules, such as those concerning the simplicity and coherence of hypotheses, Kuhnian exemplars which offer models for new solutions, and field-specific concrete rules which ‘. . . tell scientists to favour conjectures that bear certain relationships to other theoretical claims in the discipline’ (ibid., p. 41). Not only do these arguments fail to defend the Darwinian analogy against the accusation that epistemic variations are not blind, they actually support an alternative ‘Lamarckian’ analogy. We have already seen the implausibility of the thesis that epistemic variations are generated randomly: the very selection that hides the chaos is what is implausible. The appeal to preadaptations to support this thesis is no less mistaken. It is true that, in the biological world, mutations and recombinations can only occur within, or elaborate on, existing genetic material, and that even then there are additional constraints since, for example, some genes mutate less often than others. But the crucial point is that the new variations are blind: they are not directed towards the needs of the organism. Furthermore, the organism cannot choose what genetic material or preadaptations it has available, nor deliberately borrow genes or organs from other species (including those long extinct) because they suit its needs. It is quite different with ideas: narrowing the field involves pre-selection by the scientists involved – often from theories, ideas or disciplines quite unconnected with the theory under challenge or long abandoned by the scientific community – according to criteria derived from the nature of the problem faced. The claim being made here is not just an empirical one: that if we examine the activity of scientists we find purposeful innovation. It is also a point of logic: problems presuppose a goal and something can only count as a tentative solution to a problem if it aims towards that goal. The invocation of heuristics to guide or direct the generation of innovations destroys the Darwinian analogy. Biological preadaptations may circum-

576 scribe the range of possible variations but they do not guide them. Guiding presupposes a ‘goal’ or ‘target’ and a ‘problem’ of reaching it, and such notions have no place in the mechanisms of organic evolution by natural selection. They may be involved in artificial selection by animal and plant breeders, but then only in the selection, not in the generation, of novel variations. It is true that since the advent of genetic engineering it has been possible for breeders to introduce new genetic variants deliberately, but this introduces a direct process along side what had been an entirely indirect one. While existing theories and ideas may be analogous to organic preadaptations, heuristics are not: heuristics do more than merely restrict variations, they direct them. Of course, pre-existing theories, ideas about scientific method, heuristics, the prevailing educational practices, individual psychology, the social milieu and so on, are amongst the factors involved in the production of scientific innovations: they help to determine the response a scientist makes to a problem. But this is to say that they are precisely what is required to constitute the direct mechanism involved in a Lamarckian process of evolutionary change. What, in Section 4, I called the second component of Lamarck’s theory, proposes a mechanism by which the demands of the environment modify the constitution of an organism, the change being passed on to future generations. While clearly unacceptable in organic evolution, such a mechanism is not only plausible in evolutionary epistemology, the arguments of Richards, Stein and Lipton show – albeit unintentionally – that it exists. The demands of the scientific environment are a major factor in bringing about evolutionary changes in lineages of scientific theories, concepts, organisations, social groupings, experimental techniques, and so on. The process involved is what I have called a direct one, and the beliefs, attitudes and general world view of those engaged in science are an important part of that process. Obviously, this is one of the points at which intentionality enters the picture. There is no thaumaturgical method which guarantees to solve problems or any logical formula for discovery, but scientists are rarely reduced to making random guesses. As Hull says (1982, p. 306) ‘Science is as goal-directed a process as exists, but it must be carried on in the absence of fore-knowledge of the goal.’ Scientists employ their theories, their understanding of scientific method, their hunches about the truth and so forth, to enable them to choose goals and devise ways of achieving them. In so doing they cause the lineages of science to evolve or even to terminate. There is another group of arguments amongst evolutionary epistemologists, about the heredity involved in the different spheres. The lineages which constitute the subjects of evolution – that which can be said to change – involve the transmission of information from evolutionary product to evolu-

577 tionary product. This flow of information contributes to the preservation of the identity of the lineage and enables us to pick it out as the subject of the change. In organic evolution information is transmitted and conserved through time by genetic inheritance, while in sociocultural evolution this is achieved by such processes as teaching and learning, reading, imitation and so forth. These latter processes, it is claimed, take the form of inheritance of acquired characteristics, and it is not surprising that numerous authors have seen this as an important difference; one which distinguishes cultural evolution as Lamarckian (e.g. Popper 1975, 1979; Toulmin 1972; Cohen 1973; Campbell 1979; Losee 1977; Thagard 1980; Sterelny 1994; Gould 1996). In the organic world a mutation takes many generations before it spreads through the population, during which time it is subject to selection. By contrast, in science ideas, concepts, theories and practices can be passed from one individual or community to another immediately they appear, and they do not have to be subject to a selective process. Those who favour the Darwinian model have reacted either by accepting this Lamarckian element in the process, but counting it as relatively unimportant (e.g. Popper 1975; Toulmin 1972) or by denying that transmission in the sociocultural realm is Lamarckian. For example, Hull (1982, 1988) has argued that this thesis rests on the acceptance of a mere caricature of Lamarck’s ideas: that organisms evolve because of their desires and intentions. Hull argues that, if this calumny is avoided, the thesis collapses: ‘On a literal reading, it is not an instance of inheritance: on a metaphorical interpretation, the things being transmitted are not characteristics but the analogues to genes’ (Hull 1982, pp. 278–279). At this point the debate becomes yet more complex, because we have to decide whether distinctions that have been fundamental in genetics since Weismann, can be applied in the sociocultural sphere: whether we can identify plausible analogues of the phenotype/genotype and the soma/germline distinctions. This leads naturally to a parallel debate about whether the replicator/interactor distinction can be applied outside organic evolution. For example, Rosenberg (1992) and Sterelny (1994) have argued, in response to Hull (1988), that such distinctions cannot be found in science in any straightforward or useful form. They claim that while Hull was justified in rejecting the claim that sociocultural inheritance is Lamarckian, he did so for the wrong reason. It cannot be Lamarckian because the soma/germline distinction does not apply in that sphere, and this distinction is necessary if we are to distinguish between Lamarckian and Weismannian inheritance (Sterelny 1994). Once again it is possible to cut through these debates by attending to the nature of the mechanisms involved. What is important about the inheritance

578 of acquired characters is the nature of the characters. If they are determined by environmental factors in such away that they cause the evolving subject to evolve so as to suit the demands of the environment, then selection plays no significant role and the process is a direct one, not Darwinian. To illustrate this let us suppose that inheritance is by a process akin to, but not identical with, Darwin’s pangenesis. In this case the environment would impinge on the somatic material of the organism and modify it; information about these modifications would be transmitted to the sex cells and thence to the next generation. This is clearly a form of inheritance of acquired characters. Now suppose that all modifications caused by the impact of the environment are passed on in this way, irrespective of their nature or usefulness: every bruise and injury as well as strengthened muscles or skilled movement. The result would be an accumulation of almost random variations rather than any form of adaptation. Lamarck overcame this problem by supposing that mechanisms are in place to ensure that when the environment impacts on the organism, it responds in an appropriate and beneficial way. These are direct mechanisms. To the extent that Darwin proposed that the ‘gemmules’ reaching the sex cells reflect the effects of use and disuse on the organs from which they come, he too was proposing a direct mechanism. But, of course, Darwinians have a better solution: they can argue that those organisms which have been modified by their environment in ways which assist their survival would be more likely to survive and transmit their acquired characters. This is an indirect mechanism: the characteristics arise blindly but are then selected before they can be passed on. The important difference is not the means of inheritance but the nature of the mechanism producing the evolutionary change. In Weismannian inheritance, mutagens in the environment may frequently be the cause of the new variations without this making it ‘Lamarckian’. Hull (1988, p. 403) characterises Weismannian inheritance as that in which ‘. . . there is no correlation between the needs of an individual and the variations that occur.’ But the essential point is that there is no direct causal mechanism in place to generate such a correlation. To illustrate this, consider a case of what Toulmin (1972) called ‘coupled’ evolution in which the same factors which do the selecting also induce the novel variations.3 Suppose that organisms of a certain species are living in an environment containing very high levels of radiation. The radiation might select those individuals most tolerant of it, and also induce mutations of a random nature. Some of these mutations might, by chance, bestow greater radiation tolerance on the recipients, thus producing an evolutionary change. What makes this an indirect or Darwinian process is that there is no mechanism in place to ensure the appearance of the mutations required by the environment: the novel variations

579 appear blindly and are then selected. In the case of science, on the contrary, the mechanisms are in place to try to ensure that decisions about innovations and the abandonment of lines of research, are made according to the needs of the situation. These changes may then be transmitted directly to the scientific community. It can be seen from these arguments that there are aspects of the evolution of science which are clearly non-Darwinian. However, nothing that has been said so far rules out the possibility that a Darwinian mechanism may sometimes operate in the evolution of science. Some innovations may be more or less blind and it seems intuitively obvious that there is a selection process, of considerable severity, operating so as to terminate lineages of ideas, theories, experimental procedures and so on. The existence and nature of this selection process will not be discussed at length here but there are some observations that need to be made. If we visualise science as a skein of lineages – lineages of concepts, theories, experimental procedures, social groups and so on – then many of those lineages will show evolutionary change and, given time, many well terminate in what appears to be a process of selection. However, we need to look carefully at what mechanism is operating. A line of research, a theory or experimental method may be abandoned by decision of those involved because it is believed that they cannot overcome anomalies or be made to work. In such cases the termination of the lineage is, in fact, a kind of novel innovation produced by a direct process involving judgements about the demands of the scientific environment. The agents who are promoting the theories or undertaking the research may, or may not, be the same as those criticising and performing damning experiments; the criteria of ‘selection’ may be exactly the factors producing the abandonment. Thus the actual mechanism at work is not one of selection in the sense required by a Darwinian; it uses the same rational processes as those that introduce innovations. Notice that this undermines Popper’s distinction between selectivist or Darwinian approach to science which ‘. . . only allows instruction from within – from within the structure itself’, and the inductivist or Lamarckian approach which ‘. . . operates with the idea of instruction from without, or from the environment.’ (Popper 1975, p. 88. Emphasis in the original.) Even in biology the within/without distinction is not straightforward, especially if we accept Dawkins’ idea of the extended phenotype (Dawkins 1982). But at least there is a kind of intuitive obviousness about the claim that ‘new instructions’ in the form of gene mutations occur within the organism, while the selection mechanism is outside in the environment. However, in the evolution of science the distinction is elusive. Popper never specifies what is the scientific equivalent of an organism, and he shifts the boundary between the ‘within’

580 and ‘without’ to suit his argument. When he wants the new instructions or tentative theories to come from within the structure, the scientists are on the inside doing the creating; but when he is discussing the hostile environment in which the theories have to survive, the scientists are on the outside doing the criticising and conducting the potentially disconfirmatory experiments. However, there may be a sting in the tail for those who oppose the Darwinian model of the development of science. If we assume a realist position and see the scientific enterprise as one of discovering the nature of an independent reality; and if we accept that scientists are neither clairvoyant nor prescient, then there may be a crucial Darwinian process at work. On these assumptions, reality places constraints on the outcomes of our experiments but it remains the scientist’s job to interpret what they mean. The response made to the experimental findings must arise, not from ‘reality’, but from within the system of beliefs, theories and goals which constitute the social practice of science. The innovations so produced must inevitably be blind as far as reality is concerned, but reality acts as the final arbiter. GatensRobinson (1993) criticises Hull (1988) for employing ‘reality’ to provide the goal and direction of science, while clinging to a Darwinian model of scientific change which, if it is truly Darwinian, is strictly non-teleological. But the Darwinian process identified here avoids this criticism, because it operates so as to make science evolve in what appears to be a goal directed way, when in fact it is not: this, after all, is one of the most remarkable characteristics of Darwin’s great discovery. Of course, the work of scientists is goal directed, but the goals are of their own making and they may or may not correspond to the world. The under-determination of theories by data ensures that the direct mechanisms operating within science predominate, but there is a Darwinian selective process beyond them.

6. Conclusion Science changes over time and it is not unreasonable to see some of these changes as evolutionary. Although, as we saw, the criteria for the application of that epithet are very broad, all evolution stands in need of explanation, both as to why it happened and why it took the form that it did. In looking for an explanatory mechanism it is not surprising that philosophers turned to biology for the best understood and most successful theory, and took the Darwinian theory as a paradigm. However, there have been numerous criticisms made of this choice and a veritable thicket of argument has been generated. Many protagonists have favoured what they saw as a Lamarckian model, while others have favoured a hybrid.

581 In this paper I have tried to cut through the debates concerning the nature of the mechanisms at work in sociocultural evolution by beginning from an analysis of the principal notions involved. The discussion has shown that there are two kinds of process capable of producing evolutionary change: dubbed ‘direct’ and ‘indirect’. It is not always easy to identify which is operating in any particular case, but once identified it can be seen that, although these mechanisms may work side by side, hybrids are not possible. These ideas were then applied in an examination of a selection of the arguments within evolutionary epistemology. Those arguments purporting to show that the evolution of science could not be Darwinian because of the pattern and the rate of change, were shown to be inconclusive. However, it was possible to reach firm conclusions concerning the more crucial debates about the origin of the variations and the mechanism of inheritance. It was shown that the principal mechanisms at work in the development of science are of the direct kind. Since much has been said about the use and misuse of the term ‘Lamarckian’ it may be thought wise to say only that this means the main processes are non-Darwinian. However, I suggest that they can be counted as Lamarckian, because they belong to the same family and are analogous to the second of the two components of his theory identified in Section 4. What of the criticisms levelled at Lamarck’s theory? The first was that he explains the process of evolution in terms of wants and conscious strivings on the part of organisms. This criticism is almost certainly unjustified but, in any case, it looses its force when moved from biology to evolutionary epistemology where purposeful agents are at work. The second criticism was aimed at the inheritance of acquired characteristics and we have seen that this feature of his theory becomes a virtue when applied to the evolution of science. The third was by far the most damning: the theory is empty since it purports to explain evolution but, in fact, offers no explanation at all. It tells us, in the case of organic evolution, that animals respond to the needs imposed on them by the environment by modifying their behaviour and ultimately their structure, but the theory does not tell us why animals makes these adaptations or, indeed, why they respond at all. This, it was said, can only be given a Darwinian explanation. But, once again, the situation is transformed when we move to evolutionary epistemology. The innovations are produced because of, and in accordance with, the understanding, knowledge and beliefs current amongst the people involved, in response to emerging difficulties. Of course, the reason why we respond in this way in the face of constraints and problems, and don’t just change the subject, hibernate, or take up golf, may ultimately be explained by Darwinian evolution but, once again, the origin of the process does not determine its nature. The criticism that was damning

582 when applied to the evolution of our cognitive faculties, loses its power when directed at the products of those faculties. Indirect or Darwinian-like mechanisms may play a minor role within the social practice of science. Some innovations may occur blindly and some lineages may be terminated by a selective process unrelated to the origin of those innovations, but it is hoped that the preceding arguments have shown that this is generally not the case. It may be that at the beginnings of science it was much more Darwinian than now, but this element would inevitably decline and be replaced by the process described here, as reflection on science and its methods increased. However, if the realist thesis is correct, then there may be a non-teleological, Darwinian process working around science to adapt its theories to the real world. The conclusions reached here shed some light on the issues of intentionality, rationality and progress, concerning science. Some philosophers (e.g. Toulmin 1972; Popper 1975) have seen, as one of the attractions of an evolutionary approach to epistemology, that it shifts the locus of the rationality of science away from the individual scientist and places it in the impersonal mechanism of scientific progress. These issues have always been a problem within evolutionary epistemology because Darwinian theory – the favoured model – is a non-teleological theory of change, not of progress. It is neither rational nor irrational, it is non-rational, and the brilliant success of Darwinian theory within science (in biology), cannot justify its use to explain the success of science as a whole. The direct or Lamarckian model described here returns the locus of intentionality and rationality to the scientists, either as individuals or as members of a group.

Notes 1 This point may seem almost too obvious to make because we are used to thinking of changes in physical objects, the properties of which are familiar to us; but when we are dealing with more exotic areas – such as organic evolution or evolutionary epistemology – the subjects and their properties become contentious. 2 This distinction is similar to, but more general than, those made by Popper (1975) who makes a not altogether satisfactory distinction between ‘instruction’ and ‘selection’; Plotkin (1987, 1991, 1994) by which he classifies all evolutionary theories into two categories, ‘instructionalist’ and ‘selectionist’; Sober (1984) who distinguishes between ‘developmental’ and ‘variational’ explanations; and the two processes of social change employed by Harré (1979). 3 Toulmin thought that organic evolution was decoupled while the evolution of science was coupled, so he would not have liked this example. Nonetheless it meets his definition.

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