Chapter 2: Can Evolution be Accounted for Solely in Terms of Mechanical Causation? by L. Charles Birch
L. Charles Birch is Challis Professor of Biology at the University of Sydney.
What happened to evolution? The happenings we know a lot about, thanks to evolutionary biology, particularly of the last four decades, are the roles of mutation, recombination of genes in sexual reproduction resulting in a great diversity of gene arrangements, and natural selection. These are the main mechanisms of the so-called Neo-Darwinian theory of evolution. There are of course many mechanisms that are involved in these concepts, such for example as genetic assimilation established by Waddington (1957), but they may all be regarded as aspects, albeit subtle ones, of the three main mechanisms mentioned. The sum total of them presents a mechanistic world picture of the evolutionary process. It has been eminently successful in explaining transformation phenomena, although less successful in prediction. A brief but cogent account of the modern view is given by Waddington (1969).
What these mechanisms help us to understand is the way in which organisms are transformed in time, genetically, anatomically, physiologically and behaviorally in adaptation to environment. At that level the theory seems to be remarkably successful. One of the great achievements of modern evolutionary theory has been the quantification of many of these processes. The theoretical model of Neo-Darwinism is a quantitative model. It rests on well-attested concepts and has great explanatory value.
The terms ‘mechanism’ and ‘Mechanistic world picture’ may be regarded as the conception according to which the universe is seen as a machine or contrivance and all that is in it as smaller machines or contrivances which, once set in motion, perform as they do, by virtue of their construction (Dijksterhuis 1961, p. 495). Having originated in the physical sciences, the mechanical analogy was taken over by the biological sciences as they became established as sciences in their own right. As a result it is true to say now, as Whitehead (1926, p. 128) said decades ago, that "It is orthodox to hold that there is nothing in biology but what is physical mechanism under somewhat complex circumstances . . . the appeal to mechanism on behalf of biology was in its origin an appeal to the well-attested self-consistent physical concepts as expressing the basis of all natural phenomena. But at present there is no such system of concepts." To this latter claim I shall return later. The main point of Whitehead’s remark is that biology has an orthodoxy; it is mechanism based on physics.
There are, however, outstanding problems in evolution that remain unaccounted for when we come to look at evolution in a comprehensive way. In particular, there is a qualitative side to evolution which escapes interpretation that is solely concerned with mechanical causes. Evolutionary biologists, with some notable exceptions, such as Dobzhansky (1967), Wright (1969), Waddington (1961) Rensch (1961), and Thorpe (1965), scarcely seem to recognize that this is a problem requiring interpretation. Where the problem is recognized it is usually in relation to two ‘events’ in evolutionary history: the emergence of life and the emergence of mind. ‘Livingness’ and mentality I take to have qualitative as well as quantitative aspects.
The Concept of Emergence
Dobzhansky (1967, p. 32) has said that "the origin of life and the origin of man were evolutionary crises, turning points, actualizations of novel forms of being. These radical innovations can be described as emergences, or transcendences, in the evolutionary process." In the sentence that immediately follows this quotation, which is about the human mind, Dobzhansky says that evolution is a source of novelty, of forms becoming what did not occur at all in the ancestral state. It is this new aspect which leads him to use the words ‘emergence’ or ‘transcendence.’ C. Lloyd Morgan, in his book Emergent Evolution (1923), wrote of the emergence of life and mind as ‘miracles’ in the sense of something that is not understood. He with other ‘emergent evolutionists’ such as J. C. Smuts believed that these emergent properties could not be understood in terms of the laws of physics and chemistry, but that some new laws come into existence with the new qualities. Morgan considered there to be different laws at the level of the inorganic, the organic, and the human (Lloyd Morgan 1923, p. 43). By contrast, Dobzhansky clearly considers that the emergence of life and mind are to be understood according to the same evolutionary principles as are applied to anatomical or physiological characters.
The term ‘emergence,’ however, does not explain any problems. It is not a solution to a problem. As Leclerc (this book) says, "rather the term emergence signifies a problem requiring solution."
The qualities that ‘emerge’ in evolution are not, of course, just livingness and mentality. To discuss the issue as if they were is to discuss evolution as though it were punctuated with discontinuities. Modern biology has demonstrated the continuity of the evolutionary process in the sense that what has evolved constitutes a continuum without any sharp dividing lines, even between non-living and living. While the words ‘life’ and ‘mind’ refer to aspects of such great significance in the whole process that we might wish to attach special terms such as transcendence or emergence to them, we must recognize that the qualitative side of evolution, like the material side, is a continuum. The manifestation of life in an amoeba is different from that in a bacterium, and so on. I am not implying that the word ‘life’ refers simply to the qualitative, but it does include the qualitative when we recognize responsiveness and perception as evidence that living organisms are subjects for themselves and in themselves as well as objects that we observe. The problem that calls for explanation is the qualitative so far as it is evident in the whole gamut of evolutionary history.
The tradition of science since Descartes has been to start with the physicist’s atoms and molecules and attempt to account for the whole complexity of the universe, including life and mind, this way. That is the aim of molecular biology. It is the faith of mechanical determinism. The trouble is that it does not work, because there is nothing ultimate about the physicist’s atoms and molecules. It incorporates two attitudes which are radically inconsistent. As Whitehead (1926, p. 94) remarked, "A scientific realism, based on mechanism, is conjoined with an unwavering belief in the world of men and of higher animals as being composed of self-determining organisms." How you get one from another is the problem (Overman 1967, p. 166). I think it is because of this problem that Whitehead (1926, p. 157) further remarked, "a thoroughgoing evolutionary philosophy is inconsistent with materialism. The aboriginal stuff, or material, from which a materialistic philosophy starts is incapable of evolution." If we are to understand why Whitehead thought this way we need first to examine the alternative he proposed.
Whitehead reversed the situation of the mechanists (Waddington 1961, p. 19). We do not start with knowing all about atoms and molecules and then seem to understand the phenomena of biology. It is from observed phenomena in biology that we have to start, with "occasions of experience" (Whitehead 1933, p. 196). It is from these we work back to construct models of similar entities. But these models take account of the phenomena observed at the more complex levels. To use an example of Waddington (1961, p. 20), sodium chloride molecules exhibit properties which we cannot observe by studying sodium and chlorine atoms in isolation. When the compound sodium chloride is formed, it is not that something entirely new is added to sodium and chlorine atoms, but rather we now know something more about the nature of sodium and chlorine atoms then we did before. Similarly with phenomena of life. When certain arrangements of atoms of carbon, nitrogen, hydrogen, oxygen and so on exhibit properties which we recognize by the name enzymes, or other combinations are able to conduct electrical impulses as in nerve cells, it is not that something new has been added to these atoms. We have discovered something about the nature of these atoms that we did not know before. We discover that when atoms are organized in particular ways they reveal aspects of their nature not revealed in isolation. Atoms and molecules organized in brains reveal the potentiality of atoms organized in particular ways to give rise to entities with subjective experience to which we give the name mind or consciousness. Atoms that can give rise to brains that think must be different from hypothetical atoms that could under no circumstances have done this.
Evolution of the Subjective
This is the crux of our problem. Evolution has given rise to ourselves who know the existence of a subjective aspect of life in our own lives. The subjective aspect of life for us is a central fact of our existence. The conduct of human affairs is entirely determined by our recognition of foresight determining purposes which we pursue consciously. This conscious pursuit of purpose issues in conduct determined by the purpose. There is of course a whole set of mechanisms, physiological and biochemical, associated with these subjective experiences, but these are not that experience per se. A feeling is a feeling, period. Consciousness is sui generis an aspect of existence. What then is the origin of the subjective we know in our own lives?
Where in evolution did the subjective start if it started anywhere? We cannot of course be sure that anyone besides ourselves has a subjective side to life. We cannot have another’s experience. But most of us do not deny that other human beings must be like ourselves in this respect. Many of us too will be inclined to attribute feelings of pleasure and pain to the animals we know well, such as our domestic cats and dogs. We may be less willing to attribute a subjective side to organisms lower down the evolutionary scale. But that is an arbitrary decision based perhaps on their lack of a complex nervous system. It seems to me less arbitrary and more logical to go along with Jennings (quoted by Agar 1943, p. 153), who wrote after years of study on the behavior of amoebae: "I am thoroughly convinced, after long study of the behavior of this organism, that if Amoeba were a large animal, so as to come within the every day experience of human beings, its behavior would at once call forth the attribution to it of states of pleasure and pain, of hunger, desire, and the like, on precisely the same basis as we attribute these things to the dog."
It is of course commonplace that perception does not reveal to us the intrinsic nature of things, but only the way in which they act, and are acted upon by other things. The object as constructed by us in perception differs from the real object in the same way as another person’s sensory perception of myself differs from the real me. I am an experiencing subject and no one else can experience my experiencing. The position is the same in our perception of living organisms other than man and in our perception of non-living objects.
Although we cannot know another organism’s subjective experience, it is reasonable to posit that variations will depend upon the sort of nervous system and sensory system the organism has. A person deprived of eyes or of the region of the brain where vision is involved must have a subjective experience that differs from the person equipped with these organs. Animals that are color blind have a different subjective experience than those that respond to color. Furthermore, there is no logical reason to restrict the subjective to organisms with a nervous system. Plenty of organisms without nervous systems have sense organs. Even an individual cell in our bodies is a responsive entity whose behavior can be studied in tissue culture. It has no nervous system though it has other means of communication within the cell. It ‘takes account of’ other entities in its environment, including other cells. It may move toward some things and move away from others. These are the sort of criteria we use to infer subjectivity in organisms like ourselves. But why limit subjectivity to just those complex organisms? If we do that, then we imply that subjectivity ‘emerged’ out of objectivity, that there was a stage in the evolutionary sequence when from zero subjectivity there came subjectivity, or that a combination of non-mental things could produce mind. This is to imply a discontinuity in the evolution of subjectivity; from no subjectivity came subjectivity.
This argument is applied to evolution even by those who do not apply it to their own existence, which is a contradiction. We have an insider’s view of our own ‘taking account of,’ and even then only of its conscious aspects. If we admit the existence of this aspect of our existence, then we admit that our lives cannot be reduced to the status of objective entities alone. Is it not then inconsistent to suppose that, in the evolutionary process, from objectivity alone there evolved subjectivity? Since in the rest of the world besides ourselves processes of ‘taking account of’ are going on, be it in electrons or atoms or cells, then it is logical to suppose that this subject-object relationship involves subjectivity for these other entities. This is Whitehead’s proposition that you have either got to have subjectivity everywhere or nowhere. Since it is obviously in us, then it must be everywhere. Just as the discovery that sodium chloride has properties not exhibited by sodium and chlorine in isolation tells us something about the nature of sodium and chlorine which we could not otherwise know, so too the existence of subjectivity in combinations of atoms that make human brains tells us something about the nature of those atoms that make those brains. To say that is not to imply some sort of preformation theory in which the experience of brains is wrapped up in atoms before there were any brains. It is to say that in those atoms there is the germ of subjectivity and not just zero subjectivity. The germ provides the possibility or potentiality of what can exist at more complex levels of organization. The evolving architecture of matter provides the necessary processes for the evolution of subjectivity, which is an aspect of the qualitative side of the process.
If we accept this argument so far, then does it not follow that there is an activity in evolving entities (their subjective aspect) which is not described in terms of mutation and selection and all other mechanical causes of the evolutionary process? Speculation on the nature of this activity is the subject of much of process thought. It is the point at which the concept of final causation becomes relevant.
A Role for Final Causation
Final causation is a potent causal agent in our conscious lives. What we do and are is very much dependent upon our imagined future or goals. Anticipation of the future influences our present existence and activity. It is the causal agent in so-called ‘cultural evolution’ which made the difference between cave man and modern man, and will make the difference between modem men and men of the future. Is there anything at all analogous to this in pre-human evolution? That is the critical question. It is a question that raises unwelcome spectres in the minds of most biologists. It resurrects for them concepts now discarded by science as a result above all of the work of Charles Darwin -- concepts of design according to a preordained plan of a designer, or primitive transformist concepts of fishes willing to become Amphibia, or Bernard Shaw’s man willing to become superman. But none of these concepts correspond to the sense in which Whitehead and other process thinkers see the role of final causation in the world.
Final causation is concerned with one aspect of the subjective side of entities, be they humans or electrons. It is that aspect which Whitehead (1934, p. 134) called ‘subjective aim.’ Subjective aim is analogous to purpose at the human level. It is the anticipation of the future and in this sense the influence of the future on the present. It is the nisus towards completion of an event. It is the element of creativity in every event, for it involves the selection of possibilities. Each occasion of experience is in touch with possibilities from which it selects a goal regarding its ‘self-fulfillment.’ Unless there were some selection of possibilities there would be no reason for including the conception of subjective aim. It would be enough to describe an event as an effect of preceding events which automatically become the cause of other events. The selection of possibilities is the element of freedom which may, indeed, be infinitesimally small in the electronic event but substantial in a conscious mental event in human experience.
What we call ‘things’ are really not things but events. Reality is process. An entity as it is to itself is a subject, but then as it appears to another subject it is an object.
We may hardly quibble at the existence of subjective aim at the human level, but why postulate its existence in non-human entities? There seem to me to be two reasons. Firstly, it is postulated in response to the question of how it is possible to get freedom, responsiveness and purpose at the human level out of a determined, non-responsive and feelingless world of physical particles. No one has shown how that is possible. If science or the process of knowing cannot deal with purpose, then so much the worse for science and knowing. If final causation is to have a place anywhere, we must be sympathetic to a philosophy which finds it in principle everywhere, as we find mechanical causation everywhere. Secondly -- and here we enter upon a difficult argument -- subjective aim is postulated because, without it, no entity could exist. All entities are processes. "There is no thing in the universe" (Bohm 1969, p.42). When you come to analyze the nature of these processes, it is seen that they include this sort of relation to an immediate future state. As Whitehead has said somewhere, "the present is the fringe of memory tinged with anticipation." It is not within my competence to elaborate this argument in the way in which Whitehead has pursued it. Suffice it to say that the attempt to penetrate this difficult area of thought on the fuzzy boundaries of knowledge is more commendable than either erecting impenetrable walls around knowledge or supposing that knowledge has clear-cut boundaries.
Whereas subjective aim has no semblance to the role given to final causation in much pre-scientific thinking, and whereas it was science itself which eliminated the role given to final causation in the pre-scientific world, we nevertheless need to be circumspect lest we throw the baby out with the bath water. Indeed, modern physics seems to indicate a much greater awareness of this danger than modern biology. It has moved away from the mechanistic view of its fundamental particles and is finding the need for concepts that go beyond mechanism. The nature of the order of the physical world is not as simply mechanistic as biologists tend to believe. Bohm (1969, p. 18) has said that our physical theories are at present in a state of flux, that may lead to radical changes in them, such that current fundamental ideas, based on measure and metric, may also have to be replaced by new ideas, based on order." These new ideas, he suggests, will have to involve the notion of order in a way that is more fundamental than that in which order now exists in the theories of physics.
The conclusions of a reductionist mechanistic biology are dependent upon the assumption that the ultimate particles are exclusively mechanical in their properties. "Therefore," says Bohm (1969, p. 29), "the question of whether the basic laws of physics are in fact mechanical or not is of the utmost potential significance in biology." I have argued that a comprehensive evaluation of the phenomena of life leads to notions of the physical particles that are not exclusively mechanical. Now we find the physicist arguing on his own grounds that if physics comes to such a view of its subject matter this will be of the utmost significance for biology. "It does seem odd therefore," says Bohm (1969, p. 34), "that just when physics is thus moving away from mechanism, biology and psychology are moving closer to it. If this trend continues, it may well be that scientists will be regarding living and intelligent beings as mechanical, while they suppose that inanimate matter is too complex and subtle to fit into the limited categories of mechanism." But, as Bohm points out, such a position cannot stand up to critical analysis, for the molecules studied by biologists in living organisms are constituted of electrons, protons and other such particles, from which it must follow that they too are capable of behaving in ways that cannot be described in terms of mechanical concepts. There is in this view a thoroughgoing unification of nature from electronic-type events to events in the mind of man.
There are then arguments both from biology and from physics that lend credence to a view of the ultimate particles as having a subjective aspect as well as a mechanical aspect. It is within this subjective aspect that we have looked for final causation.
So far I have referred to the role of subjective aim as necessary to the constitution of the entity as it is in itself and, secondly, as being an aspect of the subjective side of existence, be it of an electron or a man. But the universe and organisms that are in it are more than a multitude of entities with subjective aims. In what way, if any, does the concept of subjective aim help us to understand the organization of organisms as we find them today and their evolution in time? Two questions call for comment.
1. How is it that subjective aims of a multitude of cells in a living organism relate to the subjective aim of the whole organism? The same question can of course be asked concerning the organization of fundamental particles into atoms and of atoms into molecules. It is by virtue of their physical properties that electrons and other particles combine in different ways to produce atoms, and so it is with atoms that find themselves in juxtaposition and then combine to produce molecules. The atom does not have a subjective aim to become anything that it is not. But when it combines with another atom by virtue of its physical properties, a new entity is formed and this new entity has its appropriate subjective aim. There is no sense in which atoms aim to become molecules or molecules to become cells. By their physical nature there is a great variety of possible architecture of arrangement of the fundamental building blocks. Of the many possible sorts of arrangements, no doubt some are too unstable to survive. Survival depends upon suitable environment. The concept of natural selection is appropriate both at the inorganic and organic levels.
At the cellular level, cells are subjects and the multicellular organism to which they belong is also a subject. The cell and the multi-cellular organism act causally as units and so as subjects have subjective aim. Tissues are nexus of cells; i.e., a tissue is a nexus of subjects but hardly a subject as such. What makes a nexus of cells into a subject in the higher multicellular organism is the centrally coordinating activity of the central nervous system or other centrally coordinating systems. It is such physiological mechanisms which turn nexus of cells into subjects as a whole. Natural selection determines that only those collections of animal cells that are organized into subjects survive. The plant is less coordinated as a subject than an animal and is more like a democracy of cells in which no particular group of cells has a central control. Nevertheless, there is coordination of function in plants despite the absence of a coordinating center.
2. Is there any sense in which the subjective aims of entities that exist at one stage of evolutionary history are directed toward some later stage of evolutionary history? For example, we might ask the question in this form: Once the cell had come into existence, was it destined to evolve men? Or, even more boldly, one could ask if there is any sense in which the universe and all that is in it have some movement toward "that far off divine event to which the whole creation moves," to use Tennyson’s phrase. The implication of these questions is that there is a terminus and that it is determined. There is, however, nothing to suggest that either concept applies to this universe (Whitehead 1934, p. 169). There is no single stream in evolution leading to Homo sapiens. There are two factors which give the question some metaphorical meaning. First, the possibilities of the future, though no doubt infinitely great, are yet limited. Second, these possibilities or potentialities exist within the foundation of the universe. That something is possible for this universe says something about the nature of this universe. But there is no implication that what is possible is inevitable. A third factor relevant to these questions might be that subjective aim applied to distant events. However, the concept of subjective aim in subjects below the human level is that of an anticipatory relationship to the immediate future, not to the distant future. It is possible that a wasp may have subjective aim to stock the nest with food before it lays its eggs. A consequence of this behavior is the survival of the species. But it would be ridiculous to postulate that the subjective aim of the wasp was the survival of the species. Natural selection sees to it that those wasps with appropriate subjective aims survive to reproduce.
What then is the role of subjective aim in evolution? Is it to be regarded as another force in addition to mutation and selection? The answer must surely be no. Mutation and selection are mechanical causes that tell us something of the way in which new organisms come into existence. The theory of subjective aim tells us that, unless subjective aim existed in entities, no organisms could come into existence. Organisms are entities that have subjective aim. The theory is saying that the only sort of universe in which evolution of organisms can occur is one in which the entities have subjective aim, and that there is an evolution of subjective aim alongside physical evolution. That is, it becomes more complex. It becomes conscious in man and, in so far as man can have long-range plans which he can execute, his conscious subjective aims or purposes can control the future direction of evolution. A second point the theory of subjective aim is making in relation to evolution is that the potentialities of the future are an aspect of existence that should be acknowledged as such, though a potential entity is a different sort of entity than one that is concretely realized. The potentialities of this universe are a property of this universe and make this a different sort of universe from some hypothetical universe without these potentialities. It seems to me, therefore, that the metaphysical background of process thought is far more germane to the evolutionary picture provided by biology than is the mechanistic philosophy, implicit or explicit, that so often accompanies evolutionary theory. I leave it as an open question whether this perspective is suggestive of new hypotheses that might be tested and whether such a view implies any change in the way in which biologists do biology and formulate theories.
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