Darwin, and After Darwin Volume Ii Part 15

So that, upon the whole, I do not see how on grounds of general reasoning it is logically possible to maintain Mr. Wallace's distinction between specific and generic characters in respect of necessary utility.

[132] _Origin of Species_, p. 122.

But now, and lastly, we shall reach the same conclusion if, discarding all consideration of general principles and formal reasoning, we fasten attention upon certain particular cases, or concrete facts. Thus, to select only two ill.u.s.trations within the limits of genera, it is a diagnostic feature of the genus _Equus_ that small warty callosities occur on the legs. It is impossible to suggest any useful function that is now discharged by these callosities in any of the existing species of the genus. If it be a.s.sumed that they must have been of some use to the species from which the genus originally sprang, the a.s.sumption, it seems to me, can only be saved by further a.s.suming that in existing species of the genus these callosities are in a vestigial condition--i. e. that in the original or parent species they performed some function which is now obsolete. But against these a.s.sumptions there lies the following fact. The callosities in question are not similarly distributed through all existing species of the genus. The horse has them upon all his four legs, while other species have them only upon two. Therefore, if all specific characters are necessarily due to natural selection, it is manifest that these callosities are _not_ now vestigial: on the contrary, they _must_ still be--or, at best, have recently been--of so much importance to all existing species of the genus, that not only is it a matter of selection-value to all these species that they should possess these callosities; but it is even a matter of selection-value to a horse that he should possess four of them, while it is equally a matter of selection-value to the a.s.s that he should possess only two.

Here, it seems to me, we have once more the doctrine of the necessary utility of specific characters reduced to an absurdity; while at the same time we display the incoherency of the distinction between specific characters and generic characters in respect of this doctrine. For the distinction in such a case amounts to saying that a generic character, if evenly distributed among all the species, need not be an adaptive character; whereas, if any one of the species presents it in a slightly different form, the character must be, on this account, necessarily adaptive. In other words, the uniformity with which a generic character occurs among the species of the genus is taken to remove that character from the necessarily useful cla.s.s, while the absence of such uniformity is taken as proof that the character must be placed within the necessarily useful cla.s.s. Which is surely no less a _reductio ad absurdum_ with regard to the generic character than the one just presented with regard to its variants as specific characters. And, of course, this twofold absurdity is presented in all cases where a generic character is unequally distributed among the const.i.tuent species of a genus.

[Ill.u.s.tration: Fig. 4.--Lower Teeth of Orang (after Tomes).]

But here is an ill.u.s.tration of another cla.s.s of cases. Mr. Tomes has shown that the molar teeth of the Orang present an extraordinary and altogether superfluous amount of attachment in their sockets--the fangs being not only exceedingly long, and therefore deeply buried in the jaw-bone, but also curving round one another, so as still further to strengthen the whole[133]. In the allied genera of anthropoid apes there is no such abnormal amount of attachment. Now, the question is, of what conceivable use can it _ever_ have been, either to the existing genus, or to its parent species, that such an abnormal amount of attachment should obtain? It certainly is not required to prevent dislocation of the teeth, seeing that in all allied genera, and even in man himself, the amount of attachment is already so great that teeth will break before they can be drawn by anything short of a dentist's forceps.

Therefore I conclude that this peculiarity in the dent.i.tion of the genus must have arisen in its parent species by way of what Darwin calls a "fluctuating variation," without utilitarian significance. And I adduce it in the present connexion because the peculiarity is one which is equally unamenable to a utilitarian explanation, whether it happens to occur as a generic or a specific character.

[133] _A Manual of Dental Anatomy_, p. 455.

Numberless similar cases might be quoted; but probably enough has now been said to prove the inconsistency of the distinction which our opponents draw between specific and all higher characters in respect of utility. In point of fact, a very little thought is enough to show that no such distinction admits of being drawn; and, therefore, that any one who maintains the doctrine of utility as universal in the case of specific characters, must in consistency hold to the same doctrine in the case of generic and all higher characters. And the fact that our opponents are unable to do this becomes a virtual confession on their part of the futility of the generalization which they have propounded[134].

[134] It may be observed that this distinction was not propounded by Mr. Wallace--nor, so far as I am aware, by anybody else--until he joined issue with me on the subject of specific characters.

Whether he has always held this important distinction between specific and generic characters, I know not; but, as originally enunciated, his doctrine of utility as universal was subject to no such limitation: it was stated unconditionally, as applying to all taxonomic divisions indifferently. The words have already been quoted on page 180; and, if the reader will turn to them, he may further observe that, prior to our discussion, Mr. Wallace made no allowance for the principle of correlation, which, as we have seen, furnishes so convenient a loop-hole of escape in cases where even the argument from our ignorance of possible utility appears absurd. In his latest work, however, he is much less sweeping in his statements. He limits his doctrine to the case of "specific characters" alone, and even with regard to them makes unlimited drafts upon the principle of correlation.

On what then do Mr. Wallace and his followers rely for their great distinction between specific and all other characters in respect of utility? This is the final and fundamental question which I must leave these naturalists themselves to answer; for my whole contention is, that it is unanswerable. But although I am satisfied that they have nothing on which to base their generalization, it seems worth while to conclude by showing yet one further point. And this is, that these naturalists themselves, as soon as they quit merely abstract a.s.sertions and come to deal with actual facts, contradict their own generalization. It is worth while to show this by means of a few quotations, that we may perceive how impossible it is for them to sustain their generalization in the domain of fact.

As it is desirable to be brief, I will confine myself to quoting from Mr. Wallace.

"Colour may be looked upon as a necessary result of the highly complex chemical const.i.tution of animal tissues and fluids. The blood, the bile, the bones, the fat, and other tissues have characteristic, and often brilliant colours, which we cannot suppose to have been determined for any special purpose as colours, since they are usually concealed. The external organs and integuments, would, by the same general laws, naturally give rise to a greater variety of colour[135]."

[135] _Darwinism_, p. 297.

Surely comment is needless. Have the colour of external organs and integuments nothing to do with the determining of specific distinctions by systematists? Or, may we not rather ask, are there any other "characters" which have had more to do with their delineation of animal species? Therefore, if "the external organs and integuments naturally give rise to a greater variety of colours," for non-utilitarian reasons, than is the case with internal organs and tissues; while even the latter present, for similarly non-utilitarian reasons, such variety and intensity of colours as they do; must it not follow that, on the ground of the "Laws of Growth" alone, Mr. Wallace has conceded the entire case as regards "a large proportional number of specific characters" being non-adaptive--"spontaneous" in their occurrence, and "meaningless" in their persistence?

Once more:--

"The enormously lengthened plumes of the bird of paradise and of the peac.o.c.k, can, however, have no such use [i.e. for purposes of defence], but must be rather injurious than beneficial in the birds' ordinary life. The fact that they have been developed to so great an extent in a few species is an indication of such perfect adaptation to the conditions of existence, such complete success in the battle for life, that there is, in the adult male at all events, a surplus of strength, vitality, and growth-power, which is able to expend itself in this way without injury. That such is the case is shown by the great abundance of most of the species which possess these wonderful superfluities of plumage.... Why, in allied species, the development of accessory plumes has taken different forms, we are unable to say, except that it may be due to that individual variability which has served as a starting-point for so much of what seems to us strange in form, or fantastic in colour, both in the animal and vegetable world[136]."

[136] _Darwinism_, pp. 292-3.

Here, again, one need only ask, How can such statements be reconciled with the great dogma, "which is indeed a necessary deduction from the theory of Natural Selection, namely, that none of the definite facts of organic nature, no special organ, no characteristic form or marking can exist, but which must now be, or once have been, _useful_"? Can it be said that the plumes of a bird of paradise present "no characteristic form," or the tail of a peac.o.c.k "no characteristic marking"? Can it be held that all the "fantastic colours," which Darwin attributes to s.e.xual selection, and all the "strange forms" in the vegetable world which present no conceivable reference to adaptation, are to be ascribed to "individual variability" without reference to utility, while at the same time it is held, "as a necessary deduction from the theory of Natural Selection," that _all_ specific characters must be "_useful_"? Or must we not conclude that we have here a contradiction as direct as a contradiction can well be[137]?

[137] Since the above was written both Mr. Gulick and Professor Lloyd Morgan have independently noticed the contradiction.

Nor is it any more possible to reconcile these contradictory statements by an indefinite extension of the term "correlation," than we found it to be in the cases previously quoted. It might indeed be logically possible, howsoever biologically absurd, to attribute the tail of a peac.o.c.k--with all its elaboration of structure and pattern of colour, with all the drain that its large size and weight makes upon the vital resources of the bird, with all the increased danger to which it exposes the bird by rendering it more conspicuous, more easy of capture, &c.--to correlation with some useful character peculiar to peac.o.c.ks. But to say that it is due to correlation with general "vitality," is merely to discharge the doctrine of correlation of any a.s.signable meaning.

Vitality, or "perfect adaptation to the conditions of existence," is obviously a prime condition to the occurrence of a peac.o.c.k's tail, as it is to the occurrence of a peac.o.c.k itself; but this is quite a different thing from saying that the specific characters which are presented by a peac.o.c.k's tail, although useless in themselves, are correlated with some other and useful specific characters of the same bird--as we saw in a previous chapter with reference to secondary s.e.xual characters in general. Therefore, when Mr. Wallace comes to the obvious question why it is that even in "allied species," which must be in equally "perfect adaptation to the conditions of existence," there are no such "wonderful superfluities of plumage," he falls back--as he previously fell back--on whatever unknown _causes_ it may have been which produced the peac.o.c.k's tail, when the primary _condition_ to their operation has been furnished by "complete success in the battle for life."

I have quoted the above pa.s.sages, not so much for the sake of exposing fundamental inconsistencies on the part of an adversary, as for the sake of observing that they const.i.tute a much truer exposition of "Darwinism"

than do the contradictory views expressed in some other parts of the work bearing that t.i.tle. For even if characters of so much size and elaboration as the tail of a peac.o.c.k, the plumes of a bird of paradise &c., are admitted to be due to non-utilitarian causes, much more must innumerable other characters of incomparably less size and elaboration be mere "superfluities." Without being actually deleterious, "a large proportional number of specific characters," whose utility is not apparent, must _a fortiori_ have been due to "individual variation," to "general laws which determine the production" of such characters--or, in short, to some causes other than natural selection. And this, I say, is a doctrine much more in harmony with "Darwinism" than is the contradictory doctrine which I am endeavouring to resist.

But once again, and still more generally, after saying of "the delicate tints of spring foliage, and the intense hues of autumn," that "as colours they are unadaptive, and appear to have no more relation to the well-being of plants themselves than do the colours of gems and minerals," Mr. Wallace proceeds thus:--

"We may also include in the same category those algae and fungi which have bright colours--the red snow of the Arctic regions, the red, green, or purple seaweeds, the brilliant scarlet, yellow, white or black agarics, and other fungi. All these colours are probably the direct results of chemical composition or molecular structure, and being thus normal products of the vegetable organism, need no special explanation from our present point of view; and the same remark will apply to the varied tints of the bark of trunks, branches and twigs, which are often of various shades of brown and green, or even vivid reds and yellows[138]."

[138] _Darwinism_, p. 302.

Here, as Mr. Gulick has already observed, "Mr. Wallace seems to admit that instead of useless specific characters being unknown, they are so common and so easily explained by 'the chemical const.i.tution of the organism' that they claim no special attention[139]." And whatever answer Mr. Wallace may make to this criticism, I do not see how he is to meet the point at present before us--namely, that, upon his own showing, there are in nature numberless instances of "characters which are useless without being hurtful," and which nevertheless present absolute "constancy." If, in order to explain the contradiction, he should fall back upon the principle of correlation, the case would not be in any way improved. For, here again, if the term correlation were extended so as to include "the chemical const.i.tution or the molecular structure of the organism," it would thereby be extended so as to discharge all Darwinian significance from the term.

[139] _American Journal of Science_, Vol. XL. art. I. on _The Inconsistencies of Utilitarianism as the Exclusive Theory of Organic Evolution_.

_Summary._

I will conclude this discussion of the Utility question by recapitulating the main points in an order somewhat different from that in which they have been presented in the foregoing chapters. Such a variation may render their mutual connexions more apparent. But it is only to the main points that allusion will here be made, and, in order the better to show their independent character, I will separately number them.

1. The doctrine of utility as universal, whether with respect to species only or likewise with respect to specific characters, is confessedly an _a priori_ doctrine, deduced by way of general reasoning from the theory of natural selection.

2. Being thus founded exclusively on grounds of deduction, the doctrine cannot be combated by any appeal to facts. For this question is not one of fact: it is a question of reasoning. The treatment of our subject matter is logical: not biological.

3. The doctrine is both universal and absolute. According to one form of it _all_ species, and according to another form of it _all_ specific characters, must _necessarily_ be due to the principle of utility.

4. The doctrine in both its forms is deduced from a definition of the theory of natural selection as a theory, and the sole theory, of the origin of _species_; but, as Professor Huxley has already shown, it does not really follow, even from this definition, that all specific _characters_ must be "necessarily useful." Hence the two forms of the doctrine, although coincident with regard to species, are at variance with one another in respect of specific characters. Thus far, of course, I agree with Professor Huxley; but if I have been successful in showing that the above definition of the theory of natural selection is logically fallacious, it follows that the doctrine in both its forms is radically erroneous. The theory of natural selection is not, accurately speaking, a theory of the origin of species: it is a theory of the origin and c.u.mulative development of adaptations, to whatever order of taxonomic division these may happen to belong. Thus the premisses of the deduction which we are considering collapse: the principle of utility is shown not to have any other or further reference to species, or to specific characters, than it has to fixed varieties, genera, families, &c., or to the characters severally distinctive of each.

5. But, quitting all such antecedent considerations, we next proceeded to examine the doctrine _a posteriori_, taking the arguments which have been advanced in favour of the doctrine, other than those which rest upon the fallacious definition. These arguments, as presented by Mr.

Wallace, are two in number.

First, it is represented that natural selection must occupy the whole field, because no other principle of change can be allowed to operate in the presence of natural selection. Now I fully agree that this statement holds as regards any principle of change which is deleterious, but I cannot agree that it does so as regards any such principle which is merely neutral. No reason has ever been shown why natural selection should interfere with "indifferent" characters--to adopt Professor Huxley's term--supposing such to have been produced by any of the agencies which we shall presently have to name. Therefore this argument--or rather a.s.sertion--goes for nothing.

Mr. Wallace's second argument is, that utility is the only principle which can endow specific characters with their characteristic stability.

But this again is mere a.s.sertion. Moreover, it is a.s.sertion opposed alike to common sense and to observable fact. It is opposed to common sense, because it is obvious that any other principle would equally confer stability on characters due to it, provided that its action is constant, as Darwin expressly held. Again, this argument is opposed to fact, because we know of thousands of cases where peculiar characters are stable, which, nevertheless, cannot possibly be due to natural selection. Of such are the Porto Santo rabbits, the niata cattle, the ducks in St. James' Park, turkeys, dogs, horses, &c., and, in the case of plants, wheat, cabbage, maize, &c., as well as all the hosts of climatic varieties, both of animals and plants, in a state of nature.

Indeed, on taking a wide survey of the facts, we do not find that the principle of utility is any better able to confer stability of character than are many other principles, both known and unknown. Nay, it is positively less able to do so than are some of these other principles.

Darwin gives two very probable reasons for this fact; but I need not quote them a second time. It is enough to have seen that this argument from stability or constancy is no less worthless than the previous one.

Yet these are the only two arguments of a corroborative kind which Mr.

Wallace adduces whereby to sustain his "necessary deduction."

6. At this point, therefore, it may well seem that we need not have troubled ourselves any further with a generalization which does not appear to have anything to support it. And to this view of the case I should myself agree, were it not that many naturalists now entertain the doctrine as an essential article of their Darwinian creed. Hence, I proceeded to adduce considerations _per contra_.

Seeing that the doctrine in question can only rest on the a.s.sumption that there is no cause other than natural selection which is capable of originating any single species--if not even so much as any single specific character--I began by examining this a.s.sumption. It was shown first that, on merely antecedent grounds, the a.s.sumption is "infinitely precarious." There is absolutely no justification for the statement that in all the varied and complex processes of organic nature natural selection is the only possible cause of specific change. But, apart altogether from this _a priori_ refutation of the dogma, our a.n.a.lysis went on to show that, in point of actual fact, there are not a few well-known causes of high generality, which, while having no connexion with the principle of utility, are demonstrably capable of originating species and specific characters--if by "species" and "specific characters" we are to understand organic types which are ranked as species, and characters which are described as diagnostic of species.

Such causes I grouped under five different headings, viz. Climate, Food, s.e.xual Selection, Isolation, and Laws of Growth. s.e.xual Selection and Isolation are, indeed, repudiated by Mr. Wallace; but, in common I believe with all biologists, he accepts the other three groups of causes as fully adequate to produce such kinds and degrees of modification as are taken to const.i.tute specific distinction. And this is amply sufficient for our present purposes. Besides, under the head of s.e.xual Selection, it does not signify in the present connexion whether or not we accept Darwin's theory on this subject. For, in any case, the facts of secondary s.e.xual characters are indisputable: these characters are, for the most part, specific characters: and they cannot be explained by the principle of utility. Even Mr. Wallace does not attempt to do so; and the explanation which he does give is clearly incompatible with his doctrine touching the necessarily life-serving value of all specific characters. Lastly, the same has to be said of the Laws of Growth. For we have just seen that on the grounds of this principle likewise Mr.

Wallace abandons the doctrine in question. As regards Isolation, much more remains to be said in the ensuing portion of this work, while, as regards Climatic Variation, there are literally innumerable cases where changes of specific type are known to have been caused by this means.

7. To the latter cla.s.s of cases, however, it will be objected that these changes of specific type, although no doubt sufficiently "stable" so long as the changed conditions remain constant, are found by experiment not to be hereditary; and this clearly makes all the difference between a true specific change and a merely fict.i.tious appearance of it.

Well, in the first place, this objection can have reference only to the first two of the five principles above stated. It can have no reference to the last three, because of these heredity const.i.tutes the very foundation. This consideration ought to be borne in mind throughout. But now, in the second place, even as regards changes produced by climate and food, the reply is nugatory. And this for three reasons, as follows.

(_a_) No one is thus far ent.i.tled to conclude against the possible transmission of acquired characters; and, so long as there is even so much as a possibility of climatic (or any other admittedly non-utilitarian) variations becoming in this way hereditary, the reply before us merely begs the question.

(_b_) Even supposing, for the sake of argument, that acquired characters can never in any case become congenital, there remains the strong probability--sanctioned as such even by Weismann--that changed conditions of life may not unfrequently act upon the material of heredity itself, thus giving rise to specific changes which are from the first congenital, though not utilitarian. Indeed, there are not a few facts (Hoffmann's plants, Weismann's b.u.t.terflies, &c.), which can only be explained either in this way, or as above (_a_). And in the present connexion it is immaterial which of these alternative explanations we choose to adopt, seeing that they equally refute our opponents' objection. And not only do these considerations--(_a_) and (_b_)--refute this particular objection; they overturn on new and independent grounds the whole of our opponents' generalization. For the generalization is, that the principle of utility, acting through natural selection, is "necessarily" the sole principle which can be concerned in hereditary changes of specific type. But here we perceive both a possibility (_a_) and a probability (_b_), if not indeed a certainty, that quite other principles have been largely concerned in the production of such changes.

(_c_) Altogether apart from these considerations, there remains a much more important one. For the objection that fixed--or "stable"--climatic varieties differ from true species in not being subject to heredity, raises the question--What are we to understand by a "species"? This question, which was thus far purposely left in abeyance, had now to be dealt with seriously. For it would clearly be irrational in our opponents to make this highly important generalization with regard to species and specific characters, unless they are prepared to tell us what they mean by species, and therefore by characters as specific. In as far as there is any ambiguity on this point it makes entirely for our side in the debate, because even any small degree of uncertainty with regard to it would render the generalization in question proportionally unsound. Yet it is notorious that no word in existence is more vague, or more impossible to define, than the word "species." The very same men who at one time p.r.o.nounce their great generalization with regard to species, at another time a.s.severate that "a species is not a definite ent.i.ty," but a merely abstract term, serving to denote this that and the other organic type, which this that and the other systematist regards as deserving such a t.i.tle. Moreover it is acknowledged that systematists differ among themselves to a wide extent as to the kinds and degrees of peculiarity which ent.i.tle a given form to a specific rank. Even in the same department of systematic work much depends on merely individual taste, while in different departments widely different standards of delimination are in vogue. Hence, our _reductio ad absurdum_ consists in this--that whether a given form is to be regarded as necessarily due to natural selection, and whether all its distinctive characters are to be regarded as necessarily utilitarian characters, will often depend on whether it has been described by naturalist A or by naturalist B. There is no one criterion--there is not even any one set of criteria--agreed upon by naturalists for the construction of specific types. In particular, as regards the principle of heredity, it is not known of one named species in twenty--probably not in a hundred--whether its diagnostic characters are hereditary characters; while, on the other hand, even in cases where experiment has proved "constant varieties" to be hereditary--and even also cross-sterile with allied varieties--it is only some three or four living botanists who for these reasons advocate the elevation of such varieties to the rank of species. In short, as we are not engaged on any abstract question touching the principles on which species ought to have been const.i.tuted by their makers, but upon the actual manner in which they have been, the criterion of heredity must needs be disregarded in the present discussion, as it has been in the work of systematists. And the result of this is, that any objection to our introducing the facts of climatic variation in the present discussion is excluded. In particular, so far as any question of heredity is concerned, all these facts are as a.s.suredly as they are cogently relevant. It is perfectly certain that there is "a large proportional number" of named species--particularly of plants--which further investigation would resolve into climatic varieties. With the advance of knowledge, "bad species" are always increasing at the expense of "good species," so that we are now justified in concluding with Kerner, Hackel, and other naturalists best qualified to speak on this subject, that if we could know as much about the past history and present relations of the remaining good species as we do about the bad, all the former, without exception, would become resolved into the latter. In point of fact, and apart altogether from the inductive experience on which this conclusion is based, the conclusion follows "as a necessary deduction" from the general theory of descent. For this theory essentially consists in supposing either the past or the present existence of intermediate varietal forms in all cases, with the consequence that "good species"

serve merely to mark _lacunae_ in our knowledge of what is everywhere a finely graduated process of trans.m.u.tation. Hence, if we place this unquestionably "necessary deduction" from the general theory of descent side by side with the alleged "necessary deduction" from the theory of natural selection, we cannot avoid the following absurdity--Whether or not a given form is to be regarded as necessarily due to natural selection, and all its characters necessarily utilitarian, is to be determined, and determined solely, by the mere accident of our having found, or not having found, either in a living or in a fossil state, its varietal ancestry.

8. But this leads us to consider the final and crowning incongruities which have been dealt with in the present chapter. For here we have seen, not only that our opponents thus draw a hard and fast line between "varieties" and "species" in regard to "necessary origin" and "necessary utility," but that they further draw a similar line between "species"