The Definition of Evolution

I have very little interest in debating evolution. If I found the subject deeply interesting, I would have become a biologist. I do not, so I did not. I am largely agnostic on most matters pertaining to evolutionary biology, because it is very evident that from the first “evolution” was never merely a scientific theory, but was always used as a mythological basis in support of a naturalistic worldview.  The long and short of the matter is, too many scientists are dishonest about the matter for me to trust what they say, and absent years of study on my own, of a subject I care little about, I cannot  reasonably judge for myself.  Thus, for the most part, I suspend judgment.

I do maintain, as I have elsewhere, that to the extent that evolution is a legitimate scientific account of nature, that it does not and cannot, even in principle, conflict with Christianity.  Truth cannot conflict with truth—and a scientific model of a naturalistic mechanism is not even, properly understood, a competitor with truth.

But since atheists never seem to tire of discussing evolution, I am going to present what I have found most helpful as a philosopher, which is, of course, DISTINCTIONS.  Specifically, distinctions in how the concept of “evolution” may be used.

This is an excerpt from John Lennox’ God’s Undertaker: Has Science Buried God?, which I highly recommend.

The nature and scope of evolution

‘Nothing makes sense in biology except in light of evolution.’

– Theodosius Dobzhansky

‘Large evolutionary innovations are not well understood. None has ever been observed, and we have no idea whether any may be in progress. There is no good fossil record of any.’

– Robert Wesson

‘Well, as common sense would suggest, the Darwinian theory is correct in the small, but not in the large. Rabbits come from other slightly different rabbits, not from either [primeval] soup or potatoes. Where they come from in the first place is a problem yet to be solved, like much else of a cosmic scale.’

– Sir Fred Hoyle

The definition of evolution

Thus far we have been using this term as if it had a single, agreed meaning. But this is manifestly not the case. Discussion of evolution is frequently confused by failure to recognize that the term is used in several different ways, some of which are so completely non-controversial that rejection of them might indeed evidence some kind of ignorance or stupidity (but, even then, scarcely wickedness).

What, then, is evolution? Here are some of the ideas for which the term ‘evolution’ is used:

1. Change, Development, Variation. Here the word is used to describe change, without any implication for the kind of mechanism or intelligent input (or lack of it) involved in bringing about the change. In this sense we speak of the ‘evolution of the motor car’, where, of course, a great deal of intelligent input is necessary. We speak of the ‘evolution of a coastline’, where the natural processes of sea and wind, flora and fauna shape the coastline over time, plus possibly steps taken by engineers to prevent erosion. When people speak of the ‘evolution of life’ in this sense, all they mean is that life arose and has developed (by whatever means). Used in this way, the term ‘evolution’ is neutral, innocuous and uncontroversial.

2. Microevolution: variation within prescribed limits of complexity, quantitative variation of already existing organs or structures Such processes were observed by Darwin in connection with the Galapagos finch species (see also Jonathan Weiner’s detailed study1). This aspect of the theory is scarcely controversial as such effects of natural selection, mutation, genetic drift etc. are constantly being recorded.2 One classic example with which we are, sadly, all too familiar right round the world is the way in which bacteria develop resistance to antibiotics.

It is worth recording that the changes in average finch beak lengths, which had been observed during the drought period of 1977, were reversed by the rains of 1983; so that this research is more an illustration of cyclical change due to natural selection than it is of permanent improvement (or even change). This reversal is, however, not always mentioned in textbooks.3 However, one of the main studies that has been copied from textbook to textbook and heralded as one of the main proofs of evolution has come in for very serious criticism in recent years. It concerns the occurrence of industrial melanism in the peppered moth (Biston betularia). The claim is that natural selection produced a variation of the relative numbers of light moths to dark moths in a population. Light moths were more easily seen by predators than dark ones, against the dark, polluted surfaces of tree trunks, and so eventually the population would become dominated by dark moths. Of course, if this account were true, it would at best only be an example of microevolution and that only in the sense of cyclical change (no new moths were created in the process since both kinds existed to start with). Therefore it would not be controversial except insofar as examples of microevolution are frequently cited as sufficient evidence for macroevolution.

However, according to Michael Majerus, a Cambridge expert on moths, ‘the basic peppered moth story is wrong, inaccurate or incomplete, with respect to most of the story’s component parts’.4 In addition, there appears to be no evidence that peppered moths rest on tree trunks in the wild. Many photographs in textbooks, showing them doing so, have apparently been staged. In the Times Higher Educational Supplement,5 biologist Lynn Margulis is puzzled by the fact that Steve Jones still used the peppered moth in his book update of Darwin, entitled Almost like a whale,6 even though, according to her, he must know of the dubious nature of the research. When University of Chicago biologist Jerry Coyne learned of the difficulties with the peppered moth story, he wrote: ‘My own reaction resembles the dismay attending my discovery, at the age of six, that it was my father and not Santa who brought the presents on Christmas Eve.’7,8

3. Macroevolution This refers to large-scale innovation, the coming into existence of new organs, structures, body-plans, of qualitatively new genetic material; for example, the evolution of multicellular from single-celled structures. Macroevolution thus involves a marked increase in complexity. This distinction between micro and macroevolution is the subject of considerable dispute since the gradualist thesis is that macroevolution is to be accounted for simply by extrapolating the processes that drive microevolution over time, as we shall see below.

4. Artificial selection, for example, in plant and animal breeding Breeders have produced many different kinds of roses and sheep from basic stocks, by very careful selective breeding methods. This process involves a high degree of intelligent input; and so, although often cited, in particular by Darwin himself, who argued that what humans can do in a relatively short time nature could do in a long time, provides in itself no real evidence for evolution by unguided processes.

5. Molecular evolution Some scientists argue that, strictly speaking, evolution presupposes the existence of self-replicating genetic material. For instance, Dobzhansky’s view was that, since natural selection needed mutating replicators, it followed clearly that ‘prebiological natural selection is a contradiction in terms’.9 However, the term ‘molecular evolution’ is now commonly used to describe the emergence of the living cell from non-living materials.10 This language usage can easily obscure the fact that the word ‘evolution’ here cannot mean a Darwinian process in the strict sense.

Of course, the term ‘evolution’ also covers the theories about how these things happened; the most widespread being the neo-Darwinian synthesis, according to which natural selection operates on the basis of variations that arise through mutation, genetic drift, and so on.

In light of these ambiguities in the meaning of evolution, Lewontin’s and Dawkins’ accusations become more understandable. If ‘questioning evolution’ means questioning it in senses 1, 2 or 4, then an accusation of stupidity or ignorance might be understandable. As we have already said, no one seriously doubts the validity of microevolution and cyclic change as examples of the operation of natural selection.

Confusion can easily arise, therefore, particularly when evolution is defined as microevolution. Take, for instance, the following statement about evolution by E.O. Wilson: ‘Evolution by natural selection is perhaps the only one true law unique to biological systems, as opposed to non-living physical systems, and in recent decades it has taken on the solidity of a mathematical theorem. It states simply that if a population of organisms contains multiple hereditary variants in some trait (say, red versus blue eyes in a bird population), and if one of those variants succeeds in contributing more offspring to the next generation than the other variants, the overall composition of the population changes, and evolution has occurred. Further, if new genetic variants appear regularly in the population (by mutation or immigration), evolution never ends. Think of red-eyed and blue-eyed birds in a breeding population, and let the red-eyed birds be better adapted to the environment. The population will in time come to consist mostly or entirely of red-eyed birds. Now let green-eyed mutants appear that are even better adapted to the environment than the red-eyed form. As a consequence the species eventually becomes green-eyed. Evolution has thus taken two more small steps’ [italics original].11

Quite so. But this seems to be no more than a description of microevolution – indeed, since we have red-eyed birds and blue-eyed birds in the initial population, Wilson is only describing the kind of uncontroversial cyclic change mentioned above in connection with Darwin’s finches. Thus Wilson completely bypasses the question as to whether the mechanism described can bear all the extra weight that is put upon it in any full-blown understanding of evolution – for example, answering the question, ‘Where did the birds come from in the first place?’ Yet he claims elsewhere in his article that natural selection does bear that weight. For instance he says, ‘all biological processes arose through evolution of these12 physicochemical systems through natural selection’ or again, humans are ‘descended from animals by the same blind force that created those animals’.

Furthermore, it has been repeatedly noted that, at the level discussed in Wilson’s definition, natural selection itself is essentially self-evident. Colin Patterson, FRS, in his standard text on evolution,13 presents it in the form of the following deductive argument:

• all organisms must reproduce
• all organisms exhibit hereditary variations
• hereditary variations differ in their effect on reproduction
• therefore variations with favourable effects on reproduction will succeed, those with unfavourable effects will fail, and organisms will change.

Thus natural selection is a description of the process by which the strain in a population that produces the weaker progeny eventually gets weeded out, leaving the stronger to thrive.

Patterson argues that, formulated this way, natural selection is, strictly speaking, not a scientific theory, but a truism. That is, if we grant the first three points, then the fourth follows as a matter of logic, an argument similar to that advanced by Darwin himself in the last chapter of The Origin of Species. Patterson observes that ‘this shows that natural selection must occur but it does not say that natural selection is the only cause of evolution,14 and when natural selection is generalized to be the explanation of all evolutionary change or of every feature of every organism, it becomes so all-embracing that it is in much the same class as Freudian psychology and astrology’.15 By this Patterson seems to be suggesting that it fails to satisfy Popper’s criterion of falsifiability, just as the Freudian statement that adult behaviour is due to trauma in childhood is not falsifiable. Patterson is warning us of the danger of simply slapping the label ‘natural selection’ in this generalized sense on some process, and thinking that we have thereby explained the process.

Patterson’s description highlights something very easily overlooked – the fact that natural selection is not creative. As he says, it is a ‘weeding out process’ that leaves the stronger progeny. The stronger progeny must be already there: it is not produced by natural selection. Indeed the very word ‘selection’ ought to alert our attention to this: selection is made from already existing entities. This is an exceedingly important point because the words ‘natural selection’ are often used as if they were describing a creative process, for instance, by capitalizing their initial letters. This is highly misleading as we see from the following illuminating statement by Gerd Müller, an expert on EvoDevo, an increasingly influential theory integrating evolutionary theory and developmental biology that aims to fill some of the gaps in standard neo-Darwinism. Müller writes: ‘Only a few of the processes listed above are addressed by the canonical neo-Darwinian theory, which is chiefly concerned with gene frequencies in populations and with the factors responsible for their variation and fixation. Although, at the phenotypic level, it deals with the modification of existing parts, the theory is intended to explain neither the origin of parts, nor morphological organization, nor innovation. In the neo-Darwinian world the motive factor of morphological change is natural selection, which can account for the modification and loss of parts. But selection has no innovative capacity: it eliminates or maintains what exists. The generative and ordering aspects of morphological evolution are thus absent from evolutionary theory’ [italics mine].17

Müller thus confirms what logic and even language would tell us: natural selection, by its very nature, does not create novelty. This flatly contradicts Richard Dawkins’ bold assertion cited earlier that natural selection accounts for the form and existence of all living things. Such polar opposition of views on the central thesis of neo-Darwinism raises disturbing questions as to the solidity of its scientific basis and prompts us to explore a bit further.

We now turn to the fact that the hereditable variations on which natural selection acts are random mutations in the genetic material of organisms. However, Dawkins and others are careful to inform us that evolution itself is not a purely random process. He is sufficiently impressed by calculations of mathematical probabilities to reject any notion that, say, the human eye evolved by pure chance in the time available. In his inimitable way he writes: ‘It is grindingly, creakingly, crashingly obvious that, if Darwinism were really a theory of chance, it couldn’t work. You don’t need to be a mathematician or a physicist to calculate that an eye or a haemoglobin molecule would take from here to infinity to self-assemble by sheer higgledy-piggledy luck.’18 What then is the answer? That natural selection is a law-like process that sifts the random mutations so that evolution is a combination of necessity and chance. Natural selection, we are told, will find a faster pathway through the space of possibilities. The idea here is, therefore, that the law-like process of natural selection increases the probabilities to acceptable levels over geological time.

Putting it simply, the essence of the argument is this. Natural selection favours the strong progeny over the weak in a situation where resources are limited. It helps preserve any beneficial mutation. Organisms with that mutation survive and others do not. But natural selection does not cause the mutation. That occurs by chance. The quantity of resources (food) available is one of the variable parameters in the situation. It occurred to me as a mathematician that it would be interesting to see what happens if this parameter is allowed to increase. I invite you to do a thought experiment. Imagine a situation in which resources increase so that, in the limiting case, there is food for all, the strong and the weak. As resources increase, there would seem to be less and less for natural selection to do, since most progeny would survive. What would neo-Darwinists say to this? Would they say on the basis of their chance arguments that evolution would now be less and less likely? For it would now seem that chance is doing all the work: and the neo-Darwinists have ruled that possibility out of court.

When I thought of this I was sure that it must have occurred to someone earlier, and not surprisingly it has. Indeed, in 1966, British chemist R.E.D. Clark drew attention to the fact that Darwin had been disturbed by a letter from the eminent botanist Joseph Hooker in 1862 in which Hooker argued that natural selection was in no sense a creative process.19 However, Clark had to reconstruct Hooker’s argument from Darwin’s reply as he thought Hooker’s original letter had been lost. Hooker’s letter has not been lost, however. It reads: ‘I am still very strong in holding to impotence of crossing with respect to [the] origin of species. I regard Variation as so illimitable in {animals}. You must remember that it is neither crossing nor natural selection that has made so many divergent human individuals, but simply Variation [Hooker’s emphasis]. Natural selection, no doubt has hastened the process, intensified it (so to speak), has regulated the lines, places etc., etc., etc., in which, and to which, the races have run and led, and the number of each and so forth; but, given a pair of individuals with power to propagate, and [an] infinite [time] span to procreate in, so that not one be lost, or that, in short, Natural Selection is not called upon to play a part at all, and I maintain that after n generations you will have extreme individuals as totally unlike one another as if Natural Selection had extinguished half.

‘If once you hold that natural selection can make a difference, i.e. create a character, your whole doctrine tumbles to the ground. Natural Selection is as powerless as physical causes to make a variation; the law that “like shall not produce like” is at the bottom of [it] all, and is as inscrutable as life itself. This it is that Lyell and I feel you have failed to convey with force enough to us and the public: and this is the bottom of half the infidelity of the scientific world to your doctrine. You have not, as you ought, begun by attacking old false doctrines, that “like does produce like”. The first chapter of your book should have been devoted to this and nothing else. But there is some truth I now see in the objection to you, that you make natural selection the Deus ex machina for you do somehow seem to do it by neglecting to dwell on the facts of infinite incessant variation. Your eight children are really all totally unlike one another: they agree exactly in no one property. How is this? You answer that they display the inherited differences of different progenitors – well – but go back, and back and back in time and you are driven at last to your original pair for origin of differences, and logically you must grant, that the differences between the original [MALE] & [FEMALE] of your species were equal to the sum of the extreme differences between the most dissimilar existing individuals of your species, or that the latter varied from some inherent law that had them. Now am not I a cool fish to lecture you so glibly?’20

It is interesting to note the force with which Hooker writes in ascribing ‘half the infidelity of the scientific world’ against Darwin to his failure to deal with this argument. Darwin’s reaction came in a letter (after 26 November but actually dated 20 November 1862). ‘But the part of your letter which fairly pitched me head over heels with astonishment; is that where you state that every single difference which we see might have occurred without any selection. I do and have always fully agreed; but you have got right round the subject and viewed it from an entirely opposite and new side, and when you took me there, I was astounded. When I say I agree, I must make proviso, that under your view, as now, each form long remains adapted to certain fixed conditions and that the conditions of life are in [the] long run changeable; and second, which is more important that each individual form is a self-fertilizing hermaphrodite, so that each hairbreadth variation is not lost by intercrossing. Your manner of putting [the] case would be even more striking than it is, if the mind could grapple with such numbers – it is grappling with eternity – think of each of a thousand seeds bringing forth its plant, and then each a thousand. A globe stretching to furthest fixed star would very soon be covered. I cannot even grapple with the idea even with races of dogs, cattle, pigeons or fowls; and here all must admit and see the accurate strictness of your illustration. Such men, as you and Lyell thinking that I make too much of a Deus of natural selection is conclusive against me. Yet I hardly know how I could have put in, in all parts of my Book, stronger sentences. The title, as you once pointed out, might have been better. No one ever objects to agriculturalists using the strongest language about their selection; yet every breeder knows that he does not produce the modification which he selects. My enormous difficulty for years was to understand adaptation, and this made me, I cannot but think rightly, insist so much on natural selection. God forgive me for writing at such length; but you cannot tell how much your letter has interested me, and how important it is for me with my present Book in hand to try and get clear ideas.’21

Darwin clearly feels the force of Hooker’s argument to the extent of agreeing with it though astonished at the way in which it was put. The argument seems rather important because it raises very serious questions about the kind of argument that purports to render probabilities of macro (or molecular) evolution acceptable within the timescale constraints supplied by contemporary cosmology.

Lennox, John. God’s Undertaker: Has Science Buried God? Lion Hudson. Kindle Edition.