I may perhaps be here permitted to say that, after having carefully weighed, to the best of my ability, the various arguments which have been advanced against the principle of sexual selection, I remain firmly convinced of its truth[49].
I may perhaps be here permitted to say that, after having carefully weighed, to the best of my ability, the various arguments which have been advanced against the principle of sexual selection, I remain firmly convinced of its truth[49].
I will now conclude this chapter, and with it the present volume, by offering a few general remarks on what may be termed the philosophical relations of Darwinian doctrine to the facts of adaptation on the one hand, and to those of beauty on the other. Of course we are all aware that before the days of this doctrine the facts of adaptation in organic nature were taken to constitute the clearest possible evidence of special design, on account of the wonderful mechanisms which they everywhere displayed; while the facts of beauty were taken as constituting no less conclusive evidence of the quality of such special design as beneficent, not to say artistic. But now that the Darwinian doctrine appears to have explained scientifically the former class of facts by its theory of natural selection, and the latter class of facts by its theory of sexual selection, we may fitly conclude this brief exposition of the doctrine as a whole by considering what influence such naturalistic explanations may fairly be taken to exercise upon the older, or super-naturalistic, interpretations.
To begin with the facts of adaptation, we must first of all observe that the Darwinian doctrine is immediately concerned with these facts only in so faras they occur in organic nature. With the adaptations—if they can properly be so called—which occur in all the rest of nature, and which go to constitute the Cosmos as a whole so wondrous a spectacle of universal law and perfect order, this doctrine is but indirectly concerned. Nevertheless, it is of course fundamentally concerned with them to the extent that it seeks to bring the phenomena of organic nature into line with those of inorganic; and therefore to show that whatever view we may severally take as to the kind of causation which is energizing in the latter we must now extend to the former. This is usually expressed by saying that the theory of evolution by natural selection is a mechanical theory. It endeavours to comprise all the facts of adaptation in organic nature under the same category of explanation as those which occur in inorganic nature—that is to say, under the category of physical, or ascertainable, causation. Indeed, unless the theory has succeeded in doing this, it has not succeeded in doing anything—beyond making a great noise in the world. If Mr. Darwin has not discovered a new mechanical cause in the selection principle, his labour has been worse than in vain.
Now, without unduly repeating what has already been said in Chapter VIII, I may remark that, whatever we may each think of the measure of success which has thus far attended the theory of natural selection in explaining the facts of adaptation, we ought all to agree that, considered as a matter of general reasoning, the theory does certainly refer to avera causaof a strictly physical kind; and, therefore, that no exception can be taken to the theory in this respecton grounds oflogic. If the theory in this respect is to be attacked at all, it can only be on grounds offact—namely, by arguing that the cause does not occur in nature, or that, if it does, its importance has been exaggerated by the theory. Even, however, if the latter proposition should ever be proved, we may now be virtually certain that the only result would be the relegation of all the residual phenomena of adaptation to other causes of the physical order—whether known or unknown. Hence, as far as the matter ofprincipleis concerned, we may definitely conclude that the great naturalistic movement of our century has already brought all the phenomena of adaptation in organic nature under precisely the same category of mechanical causation, as similar movements in previous centuries have brought all the known phenomena of inorganic nature: the only question that remains for solution is the strictlyscientificquestion touching the particular causes of the mechanical order which have been at work.
So much, then, for the phenomena of adaptation. Turning next to those of beauty, we have already seen that the theory of sexual selection stands to these in precisely the same relation as the theory of natural selection does to those of adaptation. In other words, it supplies a physical explanation of them; because, as far as our present purposes are concerned, it may be taken for granted, or for the sake of argument, that inasmuch as psychological elements enter into the question the cerebral basis which they demand involves a physical side.
There is, moreover, this further point of resemblance between the two theories: neither of them has anyreference to inorganic nature. Therefore, with the charm or the loveliness of landscapes, of earth and sea and sky, of pebbles, crystals, and so forth, we have at present nothing to do. How it is that so many inanimate objects are invested with beauty—why it is that beauty attaches to architecture, music, poetry, and many other things—these are questions which do not specially concern the biologist. If they are ever to receive any satisfactory explanation in terms of natural causation, this must be furnished at the hands of the psychologist. It may be possible for him to show, more satisfactorily than hitherto, that all beauty, whenever and wherever it occurs, is literally “in the eyes of the beholder"; or that objectively considered, there is no such thing as beauty. It may be—and in my opinion it probably is—purely an affair of the percipient mind itself, depending on the association of ideas with pleasure-giving objects. This association may well lead to a liking for such objects, and so to the formation of what is known as æsthetic feeling with regard to them. Moreover, beauty of inanimate nature must be an affair of the percipient mind itself, unless there be a creating intelligence with organs of sense and ideals of beauty similar to our own. And, apart from any deeper considerations, this latter possibility is scarcely entitled to be regarded as a probability, looking to the immense diversities in those ideals among different races of mankind. But, be this as it may, the scientific problem which is presented by the fact of æsthetic feeling, even if it is ever to be satisfactorily solved, is a problem which, as already remarked, must be dealt with by psychologists. As biologists we have simply to accept this feeling as a fact, and to considerhow, out of such a feeling as a cause, the beauty of organic nature may have followed as an effect.
Now we have already seen how the theory of sexual selection supposes this to have happened. But against this theory a formidable objection arises, and one which I have thought it best to reserve for treatment in this place, because it serves to show the principal difference between Mr. Darwin’s two great generalizations, considered as generalizations in the way of mechanical theory. For while the theory of natural selection extends equally throughout the whole range of organic nature, the theory of sexual selection has but a comparatively restricted scope, which, moreover, is but vaguely defined. For it is obvious that the theory can only apply to living organisms which are sufficiently intelligent to admit of our reasonably accrediting them with æsthetic taste—namely, in effect, the higher animals. And just as this consideration greatly restricts the possible scope of the theory, as compared with that of natural selection, so does it render undefined the zoological limits within which it can be reasonably employed. Lastly, this necessarily undefined, and yet most important limitation exposes the theory to the objection just alluded to, and which I shall now mention.
The theory, as we have just seen, is necessarily restricted in its application to the higher animals. Yet the facts which it is designed to explain are not thus restricted. For beauty is by no means restricted to the higher animals. The whole of the vegetable world, and the whole of the animal world at least as high up in the scale as the insects, must be taken as incapable of æsthetic feeling. Therefore, the extremebeauty of flowers, sea-anemones, corals, and so forth, cannot possibly be ascribed to sexual selection.
Now, with regard to this difficulty, we must begin by excluding the case of the vegetable kingdom as irrelevant. For it has been rendered highly probable—if not actually proved—by Darwin and others, that the beauty of flowers and of fruits is in large part due to natural selection. It is to the advantage of flowering plants that their organs of fructification should be rendered conspicuous—and in many cases also odoriferous,—in order to attract the insects on which the process of fertilization depends. Similarly, it is to the advantage of all plants which have brightly coloured fruits that these should be conspicuous for the purpose of attracting birds, which eat the fruits and so disseminate the seed. Hence all the gay colours and varied forms, both of flowers and fruits, have been thus adequately explained as due to natural causes, working for the welfare, as distinguished from the beauty, of the plants. For even the distribution of colours on flowers, or the beautiful patterns which so many of them present, are found to be useful in guiding insects to the organs of fructification.
Again, the green colouring of leaves, which lends so much beauty to the vegetable world, has likewise been shown to be of vital importance to the physiology of plant-life; and, therefore, may also be ascribed to natural selection. Thus, there remains only the forms of plants other than the flowers. But the forms of leaves have also in many cases been shown to be governed by principles of utility; and the same is to be said of the branching structure which is so characteristic of trees and shrubs, since this is theform most effectual for spreading out the leaves to the light and air. Here, then, we likewise find that the cause determining plant beauty is natural selection; and so we may conclude that the only reason why the forms of trees which are thus determined by utility appeal to us as beautiful, is because we are accustomed to these the most ordinary forms. Our ideas having been always, as it were, moulded upon these forms, æsthetic feeling becomes attached to them by the principle of association. At any rate, it is certain that when we contemplate almost any forms of plant-structure which, for special reasons of utility, differ widely from these (to us) more habitual forms, the result is not suggestive of beauty. Many of the tropical and un-tree-like plants—such as the cactus tribe—strike us as odd and quaint, not as beautiful. Be this however as it may, I trust I have said enough to prove that in the vegetable world, at all events, the attainment of beauty cannot be held to have been an object aimed at, so to speak, for its own sake. Even if, for the purposes of argument, we were to suppose that all the forms and colours in the vegetable world are due to special design, there could be no doubt that the purpose of this design has been in chief part a utilitarian purpose; it has not aimed at beauty exclusively for its own sake. For most of such beauty as we here perceive is plainly due to the means adopted for the attainment of life-preserving ends, which, of course, is a metaphorical way of saying that it is probably due to natural selection[50].
Turning, then, to the animal kingdom below the level of insects, here we are bound to confess that the beauty which so often meets us cannot reasonably be ascribed either to natural or to sexual selection. Not to sexual selection for the reasons already given; the animals in question are neither sufficiently intelligent to possess any æsthetic taste, nor, as a matter of fact, do we observe that they exercise any choice in pairing. Not to natural selection, because we cannot here, as in the case of vegetables, point to any benefit as generally arising from bright colours and beautiful forms. On the principles of naturalism, therefore, we are driven to conclude that the beauty here is purely adventitious, or accidental. Nor need we be afraid to make this admission, if only we take a sufficiently wide view of the facts. For, when we do take such a view, we find that beauty here is by no means of invariable, or even of general, occurrence. There is no loveliness about an oyster or a lob-worm; parasites, as a rule, are positively ugly, and they constitute a good half of all animal species. The truth seems to be, when we look attentively at the matter, that in all cases where beauty does occur in these lower forms of animal life, its presence is owing to one of two things—either to the radiate form, or to the bright tints. Now, seeing that the radiate form is of such general occurrence among these lower animals—appearing over and over again, with the utmost insistence, even among groups widely separated from one another bythe latest results of scientific classification—seeing this, it becomes impossible to doubt that the radiate form is due to some morphological reasons of wide generality. Whether these reasons be connected with the internal laws of growth, or to the external conditions of environment, I do not pretend to suggest. But I feel safe in saying that it cannot possibly be due to any design to secure beauty for its own sake. The very generality of the radiate form is in itself enough to suggest that it must have some physical, as distinguished from an æsthetic, explanation; for, if the attainment of beauty had here been the object, surely it might have been even more effectually accomplished by adopting a greater variety of typical forms—as, for instance, in the case of flowers.
Coming then, lastly, to the case of brilliant tints in the lower animals, Mr. Darwin has soundly argued that there is nothing forced or improbable in the supposition that organic compounds, presenting as they do such highly complex and such varied chemical constitutions, should often present brilliant colouringincidentally. Considered merely as colouring, there is nothing in the world more magnificent than arterial blood; yet here the colouring is of purely utilitarian significance. It is of the first importance in the chemistry of respiration; but is surely without any meaning from an æsthetic point of view. For the colour of the cheeks, and of the flesh generally, in thewhiteraces of mankind, could have been produced quite as effectually by the use of pigment—as in the case of certain monkeys. Now the fact that in the case of blood, as in that of many other highly coloured fluids and solids throughout the animalkingdom, the colour isconcealed, is surely sufficient proof that the colour, if regarded from an æsthetic point of view, is accidental. Therefore, when, as in other cases, such colouring occurs upon the surface, and thus becomes apparent, are we not irresistibly led to conclude that itsexhibitionin such cases is likewise accidental, so far as any question of æsthetic design is concerned?
I have now briefly glanced at all the main facts of organic nature with reference to beauty; and, as a result, I think it is impossible to resist the general conclusion, that in organic nature beauty does not exist as an endper se. All cases where beauty can be pointed to in organic nature are seemingly due—either to natural selection, acting without reference to beauty, but to utility; to sexual selection, acting with reference to the taste of animals; or else to sheer accident. And if this general conclusion should be held to need any special verification, is it not to be found in the numberless cases where organic nature not only fails to be beautiful, but reveals itself as the reverse. Not again to refer to the case of parasites, what can be more unshapely than a hippopotamus, or more generally repulsive than a crocodile? If it be said that these are exceptions, and that the forms of animals as a rule are graceful, the answer—even apart from parasites—is obvious. In all cases where the habits of life are such as to render rapid locomotion a matter of utilitarian necessity, the outlines of an animalmustbe graceful—else, whether the locomotion be terrestrial, aerial, or aquatic, it must fail to be swift. Hence it is only in such cases as that of the hippopotamus,rhinoceros, elephant, crocodile, and so forth, where natural selection has had no concern in developing speed, that the accompanying accident of gracefulness can be allowed to disappear. But if beauty in organic nature had been in itself what may be termed an artistic object on the part of a divine Creator, it is absurd to suggest that his design in this matter should only have been allowed to appear where we are able to detect other and very good reasons for its appearance.
Thus, whether we look to the facts of adaptation or to those of beauty, everywhere throughout organic nature we meet with abundant evidence of natural causation, while nowhere do we meet with any independent evidence of supernatural design. But, having led up to this conclusion, and having thus stated it as honestly as I can, I should like to finish by further stating what, in my opinion is its logical bearing upon the more fundamental tenets of religious thought.
As I have already observed at the commencement of this brief exposition, prior to the Darwinian theory of organic evolution, the theologian was prone to point to the realm of organic nature as furnishing a peculiarly rich and virtually endless store of facts, all combining in their testimony to the wisdom and the beneficence of the Deity. Innumerable adaptations of structures to functions appeared to yield convincing evidence in favour of design; the beauty so profusely shed by living forms appeared to yield evidence, no less convincing, of that design as beneficent. But both these sources of evidence have now, as it were, beentapped at their fountain-head: the adaptation and the beauty are alike receiving their explanation at the hands of a purely mechanical philosophy. Nay, even the personality of man himself is assailed; and this not only in the features which he shares with the lower animals, but also in his god-like attributes of reason, thought, and conscience. All nature has thus been transformed before the view of the present generation in a manner and to an extent that has never before been possible: and inasmuch as the change which has taken place has taken place in the direction of naturalism, and this to the extent of rendering the mechanical interpretation of nature universal, it is no wonder if the religious mind has suddenly awakened to a new and a terrible force in the words of its traditional enemy—Where is now thy God?
This is not the place to discuss the bearings of science on religion[51]; but I think it is a place where one may properly point out the limits within which no such bearings obtain. Now, from what has just been said, it will be apparent that I am not going to minimise the change which has been wrought. On the contrary, I believe it is only stupidity or affectation which can deny that the change in question is more deep and broad than any single previous change in the whole history of human thought. It is a fundamental, a cosmical, a world-transforming change. Nevertheless, in my opinion, it is a change of a non-theistic, as distinguished from an a-theistic, kind. It has rendered impossible the appearance in literature of any future Paley, Bell, or Chalmers; but it hasdone nothing in the way of negativing that belief in a Supreme Being which it was the object of these authors to substantiate. If it has demonstrated the futility of their proof, it has furnished nothing in the way of disproof. It has shown, indeed, that their line of argument was misjudged when they thus sought to separate organic nature from inorganic as a theatre for the special or peculiar display of supernatural design; but further than this it has not shown anything. The change in question therefore, although greater in degree, is the same in kind as all its predecessors: like all previous advances in cosmological theory which have been wrought by the advance of science, this latest and greatest advance has been that of revealing the constitution of nature, or the method of causation, as everywhere the same. But it is evident that this change, vast and to all appearance final though it be, must end within the limits of natural causation itself. The whole world of life and mind may now have been annexed to that of matter and energy as together constituting one magnificent dominion, which is everywhere subject to the same rule, or method of government. But the ulterior and ultimate question touching the nature of this government as mental or non-mental, personal or impersonal, remains exactly where it was. Indeed, this is a question which cannot be affected byanyadvance of science, further than science has proved herself able to dispose of erroneous arguments based upon ignorance of nature. For while the sphere of science is necessarily restricted to that of natural causation which it is her office to explore, the question touching thenature of this natural causationis one which as necessarily lies without thewhole sphere of such causation itself: therefore it lies beyond any possible intrusion by science. And not only so. But if the nature of natural causation be that of the highest order of known existence, then, although we must evidently be incapable of conceiving what such a Mind is, at least we seem capable of judging what in many respects it is not. It cannot be more than one; it cannot be limited either in space or time; it cannot be other than at least as self-consistent as its manifestations in nature are invariable. Now, from the latter deduction there arises a point of first-rate importance in the present connexion. For if the so-called First Cause be intelligent, and therefore all secondary causes but the expression of a supreme Will, in as far as such a Will is self-consistent, the operation of all natural causes must be uniform,—with the result that, as seen by us, this operation must needs appear to be what we call mechanical. The more unvarying the Will, the more unvarying must be this expression thereof; so that, if the former be absolutely self-consistent, the latter cannot fail to be as reasonably interpreted by the theory of mindless necessity, as by that of ubiquitous intention. Such being, as it appears to me, the pure logic of the matter, the proof of organic evolution amounts to nothing more than the proof of a natural process. What mode of being is ultimately concerned in this process—or in what it is that this process ultimately consists—is a question upon which science is as voiceless as speculation is vociferous.
But, it may still be urged, surely the principle of natural selection (with its terrible basis in the struggle for existence) and the principle of sexual selection(with its consequence in denying beauty to be an end in itself) demonstrate that,ifthere be design in nature, such design at all events cannot be beneficent. To this, however, I should again reply that, just as touching the major question of design itself, so as touching this minor question of the quality of such design as beneficent, I do not see how the matter has been much affected by a discovery of the principles before us. For we did not need a Darwin to tell us that the whole creation groaneth and travaileth together in pain. The most that in this connexion Darwin can fairly be said to have done is to have estimated in a more careful and precise manner than any of his predecessors, the range and the severity of this travail. And if it be true that the result of what may be called his scientific analysis of nature in respect of suffering is to have shown the law of suffering even more severe, more ubiquitous, and more necessary than it had ever been shown before, we must remember at the same time how he has proved, more rigidly than was ever proved before, that suffering is a condition to improvement—struggle for life being theraison d’êtreof higher life, and this not only in the physical sphere, but also in the mental and moral.
Lastly, if it be said that thechoiceof such a method, whereby improvement is only secured at the cost of suffering, indicates a kind of callousness on the part of an intelligent Being supposed to be omnipotent, I confess that such does appear to me a legitimate conclusion—subject, however, to the reservation that higher knowledge might displace it. For, as far as matters are now actually presented to the unbiased contemplation of a human mind, this provisionalinference appears to me unavoidable—namely, that if the world of sentient life be due to an Omnipotent Designer, the aim or motive of the design must have been that of securing a continuous advance of animal improvement, without any regard at all to animal suffering. For I own it does not seem to me compatible with a fair and honest exercise of our reason to set the sum of animal happiness over against the sum of animal misery, and then to allege that, in so far as the former tends to balance—or to over-balance—the latter, thus far is the moral character of the design as a whole vindicated. Even if it could be shown that the sum of happiness in the brute creation considerably preponderates over that of unhappiness—which is the customary argument of theistic apologists,—we should still remain without evidence as to this state of matters having formed any essential part of the design. On the other hand, we should still be in possession of seemingly good evidence to the contrary. For it is clearly a condition to progress by survival of the fittest, that as soon as organisms become sentient selection must be exercised with reference to sentiency; and this means that, if further progress is to take place, states of sentiencymustbecome so organized with reference to habitual experience of the race, that pleasures and pains shall answer respectively to states of agreement and disagreement with the sentient creature’s environment. Those animals which found pleasure in what was deleterious to life would not survive, while those which found pleasure in what was beneficial to life would survive; and so eventually, in every species of animal, states of sentiency as agreeable or disagreeable must approximately correspond with what is good forthe species or bad for the species. Indeed, we may legitimately surmise that the reason why sentiency (and,a fortiori, conscious volition) has ever appeared upon the scene at all, has been because it furnishes—through this continuously selected adjustment of states of sentiency to states of the sentient organism—so admirable a means of securing rapid, and often refined, adjustments by the organism to the habitual conditions of its life[52]. But, if so, not only is this state of matters aconditionto progress in the future; it is further, and equally, aconsequenceof progress in the past.
However, be this as it may, from all that has gone before does it not become apparent that pleasure or happiness on the one hand, and pain or misery on the other, must be present in sentient nature? And so long as they are both seen to be equally necessary under the process of evolution by natural selection, we have clearly no more reason to regard the pleasure than the pain as an object of the supposed design. Rather must we see in both one and the same condition to progress under the method of natural causation which is before us; and therefore I cannot perceive that it makes much difference—so far as the argument for beneficence is concerned—whether the pleasures of animals outweigh their pains, orvice versâ.
Upon the whole, then, it seems to me that such evidence as we have is against rather than in favour of the inference, that if design be operative in animate nature it has reference to animal enjoyment or well-being, as distinguished from animal improvement or evolution. And if this result should be found distastefulto the religious mind—if it be felt that there is no desire to save the evidences of design unless they serve at the same time to testify to the nature of that design as beneficent,—I must once more observe that the difficulty thus presented to theism is not a difficulty of modern creation. On the contrary, it has always constituted the fundamental difficulty with which natural theologians have had to contend. The external world appears, in this respect, to be at variance with our moral sense; and when the antagonism is brought home to the religious mind, it must ever be with a shock of terrified surprise. It has been newly brought home to us by the generalizations of Darwin; and therefore, as I said at the beginning, the religious thought of our generation has been more than ever staggered by the question—Where is now thy God? But I have endeavoured to show that the logical standing of the case has not been materially changed; and when this cry of Reason pierces the heart of Faith, it remains for Faith to answer now, as she has always answered before—and answered with that trust which is at once her beauty and her life—Verily thou art a God that hidest thyself.
While stating in the text, and in a necessarily general way, the evidence which is yielded by palæontology to the theory of organic evolution, I have been desirous of not overstating it. Therefore, in the earlier paragraphs of the chapter, which deal with the most general heads of such evidence, I introduced certain qualifying phrases; and I will now give the reasons which led me to do so.
Of all the five biological sciences which have been called into evidence—viz. those of Classification, Morphology, Embryology, Palæontology, and Geographical Distribution—it is in the case of palæontology alone that any important or professional opinions still continue to be unsatisfied. Therefore, in order that justice may be done to this line of dissent, I have thought it better to deal with the matter in a separate Appendix, rather than to hurry it over in the text. And, as all the difficulties or objections which have been advanced against the theory of evolution on grounds of palæontology must vary, as to their strength, with the estimate which is taken touching the degree of imperfection of the geological record, I will begin by adding a few paragraphs to what has already been said in the text upon this subject.
First, then, as to the difficulties in the way of fossils beingformed at all. We have already noticed in the text that it is only the more or less hard parts of organisms which under any circumstances can be fossilized; and even the hardest parts quickly disintegrate if not protected from the weather on land, or from the water on the sea-bottom. Moreover, as Darwin says, “we probably take a quite erroneous view when we assume that sediment is being deposited over nearly the whole bed of the sea, at a rate sufficiently quick to embed and preserve fossil remains. Throughout an enormously large proportion of the ocean, the bright blue tint of the water bespeaks its purity. The many cases on record of a formation conformably covered, after an immense interval of time, by another and a later formation, without the underlying bed having suffered in the interval any wear and tear, seem explicable only on the view of the bottom of the sea not rarely lying for ages in an unaltered condition.” Next, as regards littoral animals, he shows the difficulty which they must have in becoming fossils, and gives a striking example in several of the existing species of a sub-family of cirripedes (Chthamalinæ), “which coat the rocks all over the world in infinite numbers,” yet, with the exception of one species which inhabits deep water, no vestige of any of them has been found in any tertiary formation, although it is known that the genusChthamalusexisted through the Chalk period. Lastly, “with respect to the terrestrial productions which lived through the secondary and palæozoic periods, it is superfluous to state our evidence is fragmentary in an extreme degree. For instance, until recently not a land shell was known belonging to either of these vast periods,” with one exception; while, “in regard to mammiferous remains, a glance at the historical table in Lyell’s Manual will bring home the truth, how accidental and rare has been their preservation, far better than pages of detail. Nor is their rarity surprising, when we remember how large a proportion of the bones of tertiary mammals have been discovered eitherin caves or in lacustrine deposits; and that not a cave or true lacustrine bed is known belonging to the age of our secondary or palæozoic formations.”
But perhaps of even more importance than all these known causes which prevent the formation of fossils, is the existence of unknown causes which make for the same result. For example, the Flysch-formation is a formation of several thousand feet in thickness (as much as 6000 in some places), and it extends for at least 300 miles from Vienna to Switzerland; moreover, it consists of shale and sandstone. Therefore, alike in respect of time, space, and character, it is just such a formation as we should expect to find highly rich in fossils; yet, “although this great mass has been most carefully searched, no fossils, except a few vegetable remains, have been found.”
So much then for the difficulty, so to speak, which nature experiences in the manufacture of fossils. Probably not one per cent. of the species of animals which have inhabited the earth has left a single individual as a fossil, whereby to record its past existence.
But of even more importance than this difficulty of making fossils in the first instance, is the difficulty of preserving them when they are made. The vast majority of fossils have been formed under water, and a large proportional number of these—whether the animals were marine, terrestrial, or inhabitants of fresh water—have been formed in sedimentary deposits either of sand, gravel, or other porous material. Now, where such deposits have been afterwards raised into the air for any considerable time—and this has been more or less the case with all deposits which are available for exploration—their fossiliferous contents will have been, as a general rule, dissolved by the percolation of rain-water charged with carbonic acid. Similarly, sea-water has recently been found to be a surprisingly strong solvent of calcareous material: hence, Saturn-like, the ocean devours her own progenyas far as shells and bones of all kinds are concerned—and this to an extent of which we have probably no adequate conception.
Of still greater destructive influence, however, than these solvent agencies in earth and sea, are the erosive agencies of both. Any one who watches the pounding of the waves upon the shore; who then observes the effect of it upon the rocks broken into shingle, and on the shingle reduced to sand; who, looking behind him at the cliffs, sees there the evidence of the gradual advance of this all-pulverising power—an advance so gradual that no yard of it is accomplished until within that yard the “white teeth” have eaten well into the “bowels of the earth"; who then reflects that this process is going on simultaneously over hundreds of thousands of miles of coast-lines throughout the world; and who finally extends his mental vision from space to time, by trying dimly to imagine what this ever-roaring monster must have consumed during the hundreds of millions of years that slowly rising and slowly sinking continents have exposed their whole areas to her jaws; whoever thus observes and thus reflects must be a dull man, if he does not begin to feel that in the presence of such a destroyer as this we have no reason to wonder at a frequent silence in the testimony of the rocks.
But although the erosive agency of the sea is thus so inconceivably great, it is positively small if compared with erosive agencies on land. The constant action of rain, wind, and running water, in wearing down the surfaces of all lands into “the dust of continents to be"; the disintegrating effects on all but the very hardest rocks of winter frosts alternating with summer heats; the grinding power of ice in periods of glaciation; and last, but not least, the wholesale melting up of sedimentary formations whenever these have sunk for any considerable distance beneath the earth’s surface:—all these agencies taken together constitute so prodigious a sum of energies combined through immeasureableages in their common work of destruction, that when we try to realise what it must amount to, we can scarcely fail to wonder, not that the geological record is highly imperfect, but that so much of the record has survived as we find to have been the case. And, if we add to these erosive and solvent agencies on land the erosive and solvent agencies of the sea, we may almost begin to wonder that anything deserving the name of a geological record is in existence at all.
That such estimates of the destructive powers of nature are not mere matters of speculative reasoning may be amply shown by stating one single fact, which, like so many others where the present subject is concerned, we owe to the generalizations of Darwin. Plutonic rocks, being those which have emerged from subterranean heat of melting intensity, must clearly at some time or another have lain beneath the whole thickness of sedimentary deposits, which at that time occupied any part of the earth’s surface where we now find the Plutonic rocks exposed to view. Or, in other words, wherever we now find Plutonic rocks at the surface of the earth, we must conclude that all the sedimentary rocks by which they were covered when in a molten state have since been entirely destroyed; several vertical miles of the only kinds of rocks in which fossils can possibly occur must in all such cases have been abolishedin toto. Now, in many parts of the world metamorphic rocks—which have thus gradually risen from Plutonic depths, while miles of various other rock-formations have been removed from their now exposed surfaces—cover immense areas, and therefore testify by their present horizontal range, no less than by their previously vertical depth, to the enormous scale on which a total destruction has taken place of everything that once lay above them. For instance, the granitic region of Parime is at least nineteen times the size of Switzerland; a similar region south of the Amazon is probably larger than France,Spain, Italy, and Great Britain all put together; and, more remarkable still, over the area of the United States and Canada, granitic rocks exceed in the proportion of 19 to 12½ the whole of the newer Palæozoic formations. Lastly, after giving these examples, Darwin adds the important consideration, that “in many regions the metamorphic and granitic rocks would be found much more widely extended than they appear to be, if all the sedimentary beds were removed which rest unconformably on them, and which could not have formed part of the original mantle under which they were crystallized.”
The above is a brief condensation of the already condensed statement which Darwin has given of the imperfection of the geological record; but I think it is enough to show, in a general way, how precarious must be the nature of any objections to the theory of evolution which are founded merely upon the silence of palæontology in cases where, if the record were anything like complete, we should be entitled to expect from it some positive information. But, as we have seen in the text, imperfect though the record be, in as far as it furnishes positive information at all, this is well-nigh uniformly in favour of the theory; and therefore, even on grounds of palæontology alone, it appears to me that Darwin is much too liberal where he concludes his discussion by saying,—"Those who believe that the geological record is in any degree perfect, will undoubtedly at once reject the theory.” If in any measure reasonable, such persons ought rather to examine their title to such a belief; and even if they disregard the consensus of testimony which is yielded by all the biological sciences to the theory of evolution, they ought at least to hold their judgment in suspense until they shall have not only set against the apparently negative testimony which is yielded by geology its unquestionably positive testimony, but also well considered the causes which may—or rather must—have so gravely impaired the geological record.
However, be this as it may, I will now pass on to consider the difficulties and objections which have been brought against the theory on grounds of palæontology.
These may be classified under four heads. First, the absence of varietal links between allied species; second, the sudden appearance of whole groups of species—not only as genera and families, but even sometimes as orders and classes—without any forms leading up to them; third, the occurrence of highly organized types at much lower levels of geological strata than an evolutionist would antecedently expect; and, fourth, the absence of fossils of any kind lower down than the Cambrian strata.
Now all these objections depend on estimates of the imperfection of the geological record much lower than that which is formed by Darwin. Therefore I have arranged the objections in their order of difficulty in this respect, or in the order that requires successively increasing estimates of the imperfection of the record, if they are to be successively answered.
I think that the first of them has been already answered in the text, by showing that even a very moderate estimate of the imperfection of the record is enough to explain why intermediatevarieties, connecting alliedspecies, are but comparatively seldom met with. Moreover it was shown that in some cases, where shells are concerned, remarkably well-connected series of such varieties have been met with. And the same applies to species and genera in certain other cases, as in the equine family.
But no doubt a greater difficulty arises where whole groups of species and genera, or even families and orders, appear to arise suddenly, without anything leading up to them. Even this the second difficulty, however, admits of being fully met, when we remember that in very many cases it has been proved, quite apart from the theory of descent, that superjacent formations have been separated from one another bywide intervals of time. And even although it often happens that intermediate deposits which are absent in one part of the world are present in another, we have no right to assume that such is always the case. Besides, even if it were, we should have no right further to assume that the faunas of widely separated geographical areas were identical during the time represented by the intermediate formation. Yet, unless they were identical, we should not expect the fossils of the intermediate formation, where extant, to yield evidence of what the fossils would have been in this same formation elsewhere, had it not been there destroyed. Now, as a matter of fact, “geological formations of each region are almost invariably intermittent"; and although in many cases a more or less continuous record of past forms of life can be obtained by comparing the fossils of one region and formation with those of another region and adjacent formations, it is evident (from what we know of the present geographical distribution of plants and animals) that not a few cases there must have been where the interruption of the record in one region cannot be made good by thus interpolating the fossils of another region. And we must remember it is by selecting the cases where this cannot be done that the objection before us is made to appear formidable. In other words,unlesswhole groups of new species which are unknown in formation A appear suddenly in formation C of one region (X), where the intermediate formation B is absent; andunlessin some other region (Y), where B is present, the fossiliferous contents of B fail to supply the fossil ancestry of the new species in A (X);unlesssuch a state of matters is found to obtain, the objection before us has nothing to say. But at best this is negative evidence; and, in order to consider it fairly, we ought to set against it the cases where an interposition of fossils found in B (Y)doesfurnish the fossil ancestry of what wouldotherwisehave been an abrupt appearance of whole groups of new species in A (X). Now suchcases are neither few nor unimportant, and therefore they deprive the objection of the force it would have had if the selected cases to the contrary were the general rule.
In addition to these considerations, the following, some of which are of a more special kind, appear to me so important that I will quote them almostin extenso.