CHAPTER TWENTY: NATURAL SELECTION CONSIDERED AS W THIS EXPRESSION OCCASIONS HEN MR. DARWIN SAYS THAT natural selection is the most important means " of modification, I am not sure that I understand what he wishes to imply by the word" means." I do not see how the fact that those animals which are best fitted for the conditions of their existence commonly survive in the struggle for life, can be called in any special sense a "means" of modification. "Means is a dangerous word; it slips too easily into "cause." We have seen Mr. Darwin himself say that Buffon did not enter on "the causes or means of modification, as though these two words were synonymous, or nearly so. Nevertheless, the use of the word " means " here enables Mr. Darwin to speak of Natural Selection as if it were an active cause (which he conStantly does), and yet to avoid expressly maintaining that it is a cause of modification. This, indeed, he has not done in express terms, but he does it by implication when he writes, "Natural Selection might be most effective in giving the proper colour to each kind of grouse, and in keeping that colour when once acquired." Such language, says the late Mr. G. H. Lewes, "is misleading"; it makes "selection an agent.' It is plain that natural selection cannot be considered a cause of variation; and if not of variation, which is as the raindrop, then not of specific and generic modification, which are as the river; for the variations must make their appearance before they can be selected. Suppose that it is an advantage to a horse to have an especially hard and broad hoof, then a horse born with such a hoof will indeed probably survive in the struggle Origin of Species, Hist. Sketch, p. xiii. Physical Basis of Mind, p. 108. 1 2 for existence, but he was not born with the larger and harder hoof because of his subsequently surviving. He survived because he was born fit-not, he was born fit because he survived. The variation must arise first and be preserved afterwards. Mr. Darwin therefore is in the following dilemma. If he does not treat natural selection as a cause of variation, the Origin of Species will turn out to have no raison d'être. It will have professed to have explained to us the manner in which species has originated, but it will have left us in the dark concerning the origin of those variations which, when added together, amount to specific and generic differences. Thus, as I said in Life and Habit, Mr. Darwin will have made us think we know the whole road, in spite of his having almost ostentatiously blindfolded us at every step in the journey. The Origin of Species would thus prove to be no less a piece of intellectual sleight-of-hand than Paley's Natural Theology. If, on the other hand, Mr. Darwin maintains natural selection to be a cause of variation, this comes to saying that when an animal has varied in an advantageous direction, the fact of its subsequently surviving in the Struggle for existence is the cause of its having varied in the advantageous direction-or more simply stillthat the fact of its having varied is the cause of its having varied. And this is what we have already seen Mr. Darwin actually to say, in a passage quoted near the beginning of this present book. When writing of the eye he says, "Variation will cause the slight alterations"; 1 but the slight alterations" are the variations; so that Mr. Darwin's words come to this-that "variation will cause the variations.” 66 There does not seem any better way out of this dilemma than that which Mr. Darwin has adoptednamely, to hold out natural selection as a means of modification, and thenceforward to treat it as an efficient cause; but at the same time to protest again and again that it is not a cause. Accordingly he writes that "Natural Selection acts only by the preservation and accumulation of small inherited modifications,"1-that is to say, it has had no share in inducing or causing these modifications. Again, "What applies to one animal will apply throughout all time to all animals-that is, if they vary, for otherwise natural selection can effect nothing and again, "for natural selection only takes advantage of such variations as arise "3-the variations themselves arising, as we have just seen, from variation. 2 Nothing, then, can be clearer from these passages than that natural selection is not a cause of modification; while, on the other hand, nothing can be clearer, from a large number of such passages, as, for instance, "natural selection may be effective in giving and keeping colour," 4 than that natural selection is an efficient cause; and in spite of its being expressly declared to be only a means " of modification, it will be accepted as cause by the great majority of readers. * Mr. Darwin explains this apparent inconsistency thus: He maintains that though the advantageous modification itself is fortuitous, or without known cause or principle underlying it, yet its becoming the predominant form of the species in which it appears is due to the fact that those animals which have been advantageously modified commonly survive in times of difficulty, while the unmodified individuals perish: offspring therefore is more frequently left by the 2 Ibid., p. 88. Ibid., p. 66. favourably modified animal, and thus little by little the whole species will come to inherit the modification. Hence the survival of the fittest becomes a means of modification, though it is no cause of variation. It will appear more clearly later on how much this amounts to. I will for the present content myself with the following quotation from the late Mr. G. H. Lewes in reference to it. Mr. Lewes writes: "Mr. Darwin seems to imply that the external conditions which cause a variation are to be distinguished from the conditions which accumulate and perfect such variation, that is to say, he implies a radical difference between the process of variation and the process of selection. This I have already said does not seem to me acceptable; the selection I conceive to be simply the variation which has survived." 1 Certainly those animals and plants which are best fitted for their environment, or, as Lamarck calls it, "circonstances "-those animals, in fact, which are best fitted to comply with the conditions of their existenceare most likely to survive and transmit their especial fitness. No one would admit this more readily than Lamarck. This is no theory; it is a commonly observed fact in nature which no one will dispute, but it is not more "a means of modification" than many other commonly observed facts concerning animals. Why is "the survival of the fittest more a means of modification than, we will say, the fact that animals live at all, or that they live in successive generations, being born, continuing their species, and dying, instead of living on for ever as one single animal in the common acceptation of the term; or than that they eat and drink? The heat whereby the water is heated, the water Physical Basis of Mind, p. 109, 1878. 1 which is turned into steam, the piston on which the Steam acts, the driving wheel, etc., etc., are all one as much as another a means whereby a train is made to go from one place to another; it is impossible to say that any one of them is the main means. So (mutatis mutandis) with modification. There is no reason therefore why "the survival of the fittest" should claim to be an especial " means of modification" rather than any other necessary adjunct of animal or vegetable life. I find that the late Mr. G. H. Lewes has insisted on this objection in his Physical Basis of Mind. I observe, also, that in the very passage in which he does so, Mr. Lewes appears to have been misled by Mr. Darwin's use of that dangerous word " means," and, at the same time, by his frequent treatment of natural selection as though it were an active cause; so that Mr. Lewes supposes Mr. Darwin to have fallen into the very error of which, as I have above shown, he is evidently Struggling to keep clear-namely, that of maintaining natural selection to be a cause " of variation. Mr. Lewes then continues: "He [Mr. Darwin] separates Natural Selection from all the primary causes of variation either internal or external-either as results of the laws of growth, of the correlations of variation, of use and disuse, etc., and limits it to the slow accumulation of such variations as are profitable in the struggle with competitors. And for his purpose this separation is necessary. But biological philosophy must, I think, regard the distinction as artificial, referring only to one of the great factors in the production of species."1 The fact that one in a brood or litter is born fitter for the conditions of its existence than its brothers and sisters, and, again, the causes that have led to this one's Physical Basis of Mind, p. 107. |