CHAPTER IX.

CRITICISMS OF THE THEORY OF NATURAL SELECTION.

I will now proceed to consider the various objections and difficulties which have hitherto been advanced against the theory of natural selection.

Very early in the day Owen hurled the weight of his authority against the new theory, and this with a strength of onslaught which was only equalled by its want of judgment. Indeed, it is painfully apparent that he failed to apprehend the fundamental principles of the Darwinian theory. For he says:--

Natural Selection is an explanation of the process [of transmutation] of the same kind and value as that which has been proffered of the mystery of "secretion." For example, a particular mass of matter in a living animal takes certain elements out of the blood, and rejects them as "bile." Attributes were given to the liver which can only be predicated of the whole animal; the "appetency" of the liver, it was said, was for the elements of bile, and "biliosity," or the "hepatic sensation," guided the gland to their secretion. Such figurative language, I need not say, explains absolutely nothing of the nature of bilification[41].

[41] _Anatomy of Vertebrates_, vol. iii. p. 794.

Assuredly, it was needless for Owen to say that figurative language of this kind explains nothing; but it was little less than puerile in him to see no more in the theory of natural selection than such a mere figure of speech. To say that the liver selects the elements of bile, or that nature selects specific types, may both be equally unmeaning re-statements of facts; but when it is explained that the term natural selection, unlike that of "hepatic sensation," is used as a shorthand expression for a whole group of well-known natural causes--struggle, variation, survival, heredity,--then it becomes evidence of an almost childish want of thought to affirm that the expression is figurative and nothing more. The doctrine of natural selection may be a huge mistake; but, if so, this is not because it consists of any unmeaning metaphor: it can only be because the combination of natural causes which it suggests is not of the same adequacy in fact as it is taken to be in theory.

Owen further objected that the struggle for existence could only act as a cause of the extinction of species, not of their origination--a view of the case which again shows on his part a complete failure to grasp the conception of Darwinism. Acting alone, the struggle for existence could only cause extermination; but acting together with variation, survival, and heredity, it may very well--for anything that Owen, or others who followed in this line of criticism, show to the contrary--have produced every species of plant and animal that has ever appeared upon the face of the earth.

Another and closely allied objection is, that the theory of natural selection "personifies an abstraction." Or, as the Duke of Argyll states it, the theory is "essentially the image of mechanical necessity concealed under the clothes, and parading in the mask, of mental purpose. The word 'natural' suggests Matter, and the physical forces. The word 'selection' suggests Mind, and the powers of choice." This, however, is a mere quarrelling about words. Darwin called the principle which he had discovered by the name natural selection in order to mark the analogy between it and artificial selection. No doubt in this analogy there is not necessarily supposed to be in nature any counterpart to the mind of the breeder, nor, therefore, to his powers of intelligent choice. But there is no need to limit the term _selection_ (_se_ and _lego_, Gr. [Greek: legô]) to powers of intelligent choice. As previously remarked, a bank of sea-weed on the sea-shore may be said to have been selected by the waves from all the surrounding sand and stones. Similarly, we may say that grain is selected from chaff by the wind in the process of winnowing corn. Or, if it be thought that there is any ambiguity involved in such a use of the term in the case of "Natural Selection," there is no objection to employing the phrase which has been coined by Mr. Spencer as its equivalent--namely, "Survival of the Fittest." The point of the theory is, that those organisms which are best suited to their surroundings are allowed to live and to propagate, while those which are less suited are eliminated; and whether we call this process a process of selection, or call it by any other name, is clearly immaterial.

A material question is raised only when it is asked whether the process is one that can be ascribed to causation strictly natural. It is often denied that such is the case, on the ground that natural selection does not originate the variations which it favours, but depends upon the variations being supplied by some other means. For, it is said, all that natural selection does is to preserve the suitable variations _after they have arisen_. Natural selection does not _cause_ these suitable variations; and therefore, it is argued, Darwin and his followers are profoundly mistaken in representing the principle as one which _produces_ adaptations. Now, although this objection has been put forward by some of the most intelligent minds in our generation, it appears to me to betoken some extraordinary failure to appreciate the very essence of Darwinian doctrine. No doubt it is perfectly true that natural selection does not produce variations of any kind, whether beneficial or otherwise. But if it be granted that variations of many kinds are occurring in every generation, and that natural selection is competent to preserve the more favourable among them, then it appears to me unquestionable that this principle of selection deserves to be regarded as, in the full sense of the word, a natural cause. The variations being expressly regarded by the theory as more or less promiscuous[42], survival of the fittest becomes the winnowing fan, whose function it is to eliminate all the less fit in each generation, in order to preserve the good grain, out of which to constitute the next generation. And as this process is supposed to be continuous through successive generations, its action is supposed to be cumulative, till from the eye of a worm there is gradually developed the eye of an eagle. Therefore it follows from these suppositions (which are not disputed by the present objection), that if it had not been for the process of selection, such development would never have been begun; and that in the exact measure of its efficiency will the development proceed. But any agency without the operation of which a result cannot take place may properly be designated the cause of that result: it is the agency which, in co-operation with all the other agencies in the cosmos, produces that result.

[42] The degree in which variability is indefinite, or, on the contrary, determinate, is a question which is not yet ripe for decision--nor even, in my opinion, for discussion. But I may here state the following general principles with regard to it.

(1) It is evident that up to some point or another variations _must_ be pre-determined in definite lines. Men do not gather grapes from thorns, figs from thistles, nor even moss-roses from sweet-briars. In other words, "the nature of the organism" in all cases necessitates the limiting of variations within certain bounds.

(2) But when the question is as to what these bounds may be, we can only answer in a general way that, according to the general theory of evolution, they must be such as are imposed by heredity, coupled with the degree to which external conditions of life (and possibly also use-inheritance) are capable, in given cases, of modifying congenital characters. These are the only causes which the theory of descent can consistently recognise as producing variations in determinate directions.

(3) Inasmuch as variation presupposes the existence of parts that vary, and inasmuch as the variation of parts can only be in the alternative directions of increase or decrease around an average, it follows that, in the first instance at all events, every variation, if determinate, must be so only in one or other of these two opposite directions.

(4) In as far as variations are summated in successive generations, so as eventually to give rise to new structures, organs, mechanisms, &c., natural selection is theoretically competent to explain the facts, without our having to postulate the operation of unknown causes producing variations in determinate lines,--or not further than is stated in paragraphs 1 and 2.

(5) Nevertheless, it does not follow that there are not such other unknown causes; and, if there are, of course the importance of natural selection as a cause of adaptive modification would be limited in proportion to their number and the extent of their operation. But it is for those who, like the late Professors Asa Gray and Nägeli, maintain the existence of such causes, to substantiate their belief by indicating them.

Take any analogous case. The selective agency of specific gravity which is utilised in gold-washing does not create the original differences between gold-dust and dust of all other kinds. But these differences being presented by as many different bodies in nature, the gold-washer takes advantage of the selective agency in question, and, by using it as a cause of segregation, is enabled to separate the gold from all the earths with which it may happen to be mixed. So far as the objects of the gold-washer are concerned, it is immaterial with what other earths the gold-dust may happen to be mixed. For although gold-dust may occur in intimate association with earths of various kinds in various proportions, and although in each case the particular admixture which occurs must have been due to definite causes, these things, in relation to the selective process of the washer, are what is called accidental: that is to say, they have nothing to do with the causative action of the selective process. Now, in precisely the same sense Darwin calls the multitudinous variations of plants and animals accidental. By so calling them he expressly says he does not suppose them to be accidental in the sense of not all being due to definite causes. But they are accidental in relation to the sifting process of natural selection: all that they have to do is to furnish the promiscuous material on which this sifting process acts.

Or let us take an even closer analogy. The power of selective breeding by man is so wonderful, that in the course of successive generations all kinds of peculiarities as to size, shape, colour, special appendages or abortions, &c., can be produced at pleasure, as we saw in the last chapter. Now all the promiscuous variations which are supplied to the breeder, and out of which, by selecting only those that are suited to his purpose, he is able to produce the required result--all those promiscuous variations, in relation to that purpose, are accidental. Therefore the selective agency of the breeder deserves to be regarded as the cause of that which it produces, or of that which could not have been produced but for the operation of such agency. But where is the difference between artificial and natural selection in this respect? And, if there is no difference, is not natural selection as much entitled to be regarded as a true cause of the origin of natural species, as artificial selection is to be regarded as a true cause of our domesticated races? Here, as in the case of the previous illustration, if there be any ambiguity in speaking of variations as accidental, it arises from the incorrect or undefined manner in which the term "accidental" is used by Darwin's critics. In its original and philosophically-correct usage, the term "accident" signifies a property or quality not essential to our conception of a substance: hence, it has come to mean anything that happens as a result of unforeseen causes--or, lastly, that which is causeless. But, as we know that nothing can happen without causes of some kind, the term "accident" is divested of real meaning when it is used in the last of these senses. Yet this is the sense that is sought to be placed upon it by the objection which we are considering. If the objectors will but understand the term in its correct philosophical sense--or in the only sense in which it presents any meaning at all,--they will see that Darwinians are both logically and historically justified in employing the word "accidental" as the word which serves most properly to convey the meaning that they intend--namely, variations due to causes accidental to the struggle for existence. Similarly, when it is said that variations are "spontaneous," or even "fortuitous," nothing further is meant than that we do not know the causes which lead to them, and that, so far as the principle of selection is concerned, it is immaterial what these causes may be. Or, to revert to our former illustration, the various weights of different kinds of earths are no doubt all due to definite causes; but, in relation to the selective action of the gold-washer, all the different weights of whatever kinds of earth he may happen to include in his washing-apparatus are, _strictly speaking_, accidental. And as at different washings he meets with different proportions of heavy earths with light ones, and as these "variations" are immaterial to him, he may colloquially speak of them as "fortuitous," or due to "chance," even though he knows that at each washing they must have been determined by definite causes.

More adequately to deal with this merely formal objection, however, would involve more logic-chopping than is desirable on the present occasion. But I have already dealt with it fully elsewhere,--viz. in _The Contemporary Review_ for June, 1888, to which therefore I may refer any one who is interested in dialectics of this kind[43].

[43] Within the last few months this objection has been presented anew by Mr. D. Syme, whose book _On the Modification of Organisms_ exhibits a curious combination of shrewd criticisms with almost ludicrous misunderstandings. One of the latter it is necessary to state, because it pervades the quotation which I am about to supply. He everywhere compares "natural selection" with "the struggle for existence," uses them as convertible terms, and while absurdly stating that "Darwin defines natural selection as the struggle for existence," complains of "the liability of error, both on his own part and on the part of his readers," which arises from his not having everywhere adhered to this definition! (p. 8).

"Darwin has put forth two distinct and contradictory theories of the functions of natural selection. According to the one theory natural selection is selective or preservative, and nothing more. According to the other theory natural selection creates the variations(!) ... It certainly seems absurd to speak of natural selection, or the struggle for existence, as selective or preservative, for the struggle for existence does not preserve at all, not even the fit variations, as both the fit and the unfit struggle for existence, the unfit naturally more than the fit, and the fit are preserved, not in consequence of the struggle, but in consequence of their fitness. Suppose two varieties of the same species are driven, by an increase of their numbers, to seek for subsistence