THE SCIENTIFIC EVIDENCE OF ORGANIC EVOLUTION. By GEORGE J. ROMANES, M.A., LL.D., F.R.S. Zoological Secretary of the Linnean Society, London. PREFACE. INTRODUCTION. Several months ago I published in Although it is generally recognized the Fortnightly Review a lecture, that the Origin of Species has prowhich I had previously delivered at duced an effect both on the science the Philosophical Institutions of Edin- and the philosophy of our age which burgh and Birmingham, and which is without a parallel in the history of bore the above title. The late Mr. thought, admirers of Mr. Darwin's DARWIN thought well of the epitome genius are frequently surprised at the of his doctrine which the lecture pre- ignorance of his work which is dissented, and urged me so strongly to played by many persons who can republish it in a form which might scarcely be said to belong to the unculadmit of its being "spread broadcast tured classes. The reason of this ignoover the land," that I promised him to rance is no doubt partly due to the busy do so. In fulfillment of this promise, life which many of our bread-winners therefore which I now regard as are constrained to live; but it is also, more binding than ever-I reproduce I think, partly due to mere indolence. the essay in the "Nature Series" with There are thousands of educated persuch additions and alterations as ap-sons who, on coming home from their pear to me, on second thoughts, to be daily work, prefer reading literature desirable. The only object of the es- of a less scientific character than that say is that which is expressed in the which is supplied by Mr. Darwin's opening paragraph. LONDON, June 1, 1882. works; and therefore it is that such persons feel these works to belong to a category of books which is to them the whole process will be gained by a very large one-the books, namely, comparing it with the closely analowhich never are, but always to be read. gous process whereby gardeners and Under these circumstances I have cattle-breeders create their wonderful thought it desirable to supply a short productions; for just as these men, digest of the Origin of Species, which by always selecting their best indiany man, of however busy a life, or of viduals to breed from, slowly but however indolent a disposition, may continuously improve their stock, so find both time and energy to follow. Nature, by a similar process of selecWith the general aim of the present tion, slowly but continuously makes abstract being thus understood, I shall the various species of plants and anistart at the beginning of my subject mals better and better suited to the by very briefly describing the theory external conditions of their life. of natural selection. It is a matter of Now, if this process of continuousobservable fact that all plants and ani- ly adapting organisms to their enmals are perpetually engaged in what vironment takes place in nature at Mr. Darwin calls a "struggle for exist-all, there is no reason why we should ence." That is to say, in every gen- set any limits on the extent to which eration of every species a great many it is able to go, up to the point at more individuals are born than can which a complete and perfect adappossibly survive; so that there is in tation is achieved. Therefore we consequence a perpetual battle for life might suppose that all species would going on among all the constituent attain to this condition of perfect adindividuals of any given generation. justment to their environment, and Now, in this struggle for existence, there remain fixed. And so undoubtwhich individuals will be victorious edly they would, if the environment and live? Assuredly those which are were itself unchanging. But forasbest fitted to live; the weakest and the much as the environment-or the sum least fitted to live will succumb and total of the external conditions of life die, while the strongest and the best of almost every organic type alters fitted to live will be triumphant and more or less from century to century survive. Now it is this "survival of the (whether from astronomical, geologifittest" that Mr. Darwin calls "natural cal and geographical changes, or from selection." Nature, so to speak, selects the immigrations and emigrations of the best individuals out of each gen- other species living on contiguous eration to live. And not only so, but geographical areas), it follows that as these favored individuals transmit the process of natural selection need their favorable qualities to their off- never reach a terminal phase. And spring, according to the fixed laws of forasmuch as natural selection may heredity, it follows that the individu- thus continue ad infinitum, slowly als composing each successive gener- to alter a specific type in adaptation ation have a general tendency to be to a gradually changing environment, better suited to their surroundings if in any case the alteration thus afthan were their forefathers. And fected is sufficient in amount to lead this follows, not merely because in naturalists to denote the specific type every generation it is only the flow- by some different name, it follows er of the race that is allowed to breed, that natural selection has transmuted but also because if in any generation one specific type into another. And some new and beneficial qualities so the process is supposed to go on. happen to appear as slight variations over all the countless species of plants from the ancestral type, these will and animals simultaneously-the be seized upon by natural selection world of organic types being thus reand added, by transmission in subse-garded as in a state of perpetual, quent generations, to the previously though gradual, flux. existing type. Thus the best idea of Such, then, is the theory of natural selection, or survival of the fittest; sume the operation of higher causes and the first thing we have to notice where the operation of lower ones with regard to it is, that it offers to is sufficient to explain the observed our acceptance a scientific explanation phenomena, and all our science and of the numberless cases of apparent all our philosophy are scattered to the design which we everywhere meet winds. For the law of logic which with in organic nature For all such Sir William Hamilton called the law cases of apparent design consist only of parsimony-or the law which forin the adaptation which is shown by bids us to assume the operation of organisms to their environment, and higher causes when lower ones are it is obvious that the facts are covered found sufficient to explain the obby the theory of natural selection no served effects-this law constitutes less completely than they are covered the only logical barrier between sciby the theory of intelligent design ence and superstition. For it is Perhaps it may be answered, "The m nifest that it is always possible to fact that these innumerable cases of give a hypothetical explanation of adaptation may be accounted for by any phenomenon whatever, by refernatural selection is no proof that they ring it immediately to the intelligence are not really due to intelligent de- of some supernatural agent; so that sign." And in truth, this is an objec- the only difference between the logic tion which is often urged by minds of science and the logic of superstieven highly cultured minds-which tion consists in science recognizing a have not been accustomed to scientific validity in the law of parsimony modes of thought. I have heard an which superstition disregards. Thereeminent professor tell his class that fore I have no hesitation in saying the many instances of adaptation that this way of looking at the eviwhich Mr. Darwin discovered and de- dence in favor of natural selection is scribed as occurring in orchids, seemed not a scientific or a reasonable way to him to tell more in favor of con- of looking at it, but a purely supertrivance than in favor of natural stitious way. Let us take, for incauses; and another eminent professor stance, as an illustration, a perfectly once wrote to me that although he parallel case. When Kepler was unhad read the Origin of Species with able to explain by any known causes care, he could see in it no evidence of the paths described by the planets, he natural selection which might not resorted to a supernatural explanaequally well be adduced in favor of tion, and supposed that every planet intelligent design. But here we meet was guided in its movements by some with a radical misconception of the presiding angel. But when Newton whole logical attitude of science. supplied a beautifully simple physical For, be it observed, the exception in explanation, all persons with a scienlimine to the evidence which we are tific habit of mind at once abandoned about to consider, does not ques- the metaphysical explanation. Now, tion that natural selections may be to be consistent, the above-mentioned able to do all that Mr. Darwin professors, and all who think with ascribes to it: it merely objects to them, ought still to adhere to Kephis interpretation of the facts, be- ler's hypothesis in preference to Newcause it maintains that these facts ton's explanation; for, excepting the might equally well be ascribed to in- law of parsimony, there is certainly telligent design. And so undoubtedly no other logical objection to the statethey might, if we were all childish ment that the movements of the enough to rush into a supernatural planets afford as good evidence of explanation whenever a natural ex- the influence of guiding angels as planation is found sufficient to account they do of the influence of gravitafor the facts. Once admit the glaring- tion. ly illogical principle that we may as So much, then, for the absurdly il logical position that, granting the evi- tion as between natural selection and dence in favor of natural selection supernatural design resolves itself inand supernatural design to be equal to this: Were all the species of plants and parallel, we should hesitate for and animals separately created, or one moment in our choice. But, of were they slowly evolved? For if course, if the evidence is supposed they were specially created, the evinot to be equal and parallel-i. e., dence of supernatural design remains if it is supposed that the theory of unrefuted and irrefutable; whereas natural relation is not so competent if they were slowly evolved, that evia theory to explain the facts of adap- dence has been utterly and forever tation as is that of intelligent design destroyed. The doctrine of natural -then the objection is no longer the selection therefore depends for its one that we are considering. It is validity on the doctrine of organic quite another objection, and one evolution; for if once the fact of orwhich is not prima facie absurd; it ganic evolution were established, no requires to be met by examining how one would dispute that much of the far the theory of natural selection is adaptation was probably effected by able to explain the facts. Let us state natural selection. How much we the problem clearly. cannot say probably never shall be able to say; for even Mr. Darwin himself does not doubt that other tion have assisted in the modifying of specific types. For the sake of simplicity, however, I shall not go into this subject; but shall always speak of natural selection as the only cause of organic evolution. Let us, then, weigh the evidence in favor of organic evolution. If we find it wanting, we need have no complaints Innumerable cases of adaptation of organisms to their environment are the observed facts for which an ex- causes besides that of natural selecplanation is required. To supply this explanation two, and only two, hypotheses are in the field. Of these two hypotheses is one, intelligent design manifested in creation; and the other is natural selection manifested during the countless ages of the past. Now it would be proof positive of intelligent design if it could be shown that all species of plants and animals to make of natural theologians of towere created that is, suddenly in- day; but if we find it to be full troduced into the complex conditions measure, shaken together and running of their life; for it is quite incon- over, we ought to maintain that natuceivable that any cause other than ral theologians can no longer adhere intelligence could be competent to to the arguments of such writers as adapt an organism to its environment Paley, Bell and Chalmers without desuddenly. On the other hand, it liberately violating the only logical would be proof presumptive of natu- principle which separates science from ral selection if it could be shown that fetichism. one species becomes slowly trans- To avoid misapprehension, however, muted into another-i. e., that one set I may here add that while Mr. Darwin's of adaptations may be gradually theory is thus in plain and direct contransformed into another set of adap- tradiction to the theory of design, or tations according as changing circum- system of teleology, as presented by stances require. This would be proof the school of writers which I have presumptive of natural selection, be- named, I hold that Mr. Darwin's cause it would then become amply theory has no point of logical contact probable that natural selection might with the theory of design in the larger have brought about many, or most, sense, that behind all secondary causes of the cases of adaptation which we of a physical kind there is a primary cause of a mental kind. Therefore throughout this essay I refer to design in the sense understood by the see; and if so, the law of parsimony excludes the rival hypothesis of intelligent design. Thus the whole ques |