Popular Science Monthly/Volume 75/December 1909/The Argument for Organic Evolution Before the Origin of Species II
|THE ARGUMENT FOR ORGANIC EVOLUTION BEFORE THE ORIGIN OF SPECIES|
THE UNIVERSITY OF MISSOURI
IN the former part of this historical inquiry, it was shown that four of the arguments which rapidly made converts to the theory of evolution after 1859 rested upon principles of scientific method and facts of anatomy and physiology which were entirely familiar much more than fifteen years before that date. A similar examination must now be made of four more of the most important "evidences of evolution." Here again it will appear that the facts were known at least as early as 1844, and that their evolutionary implications were pointed out by Robert Chambers, Herbert Spencer or other pre-Darwinian writers. It will also appear that the flaws and gaps in the evidence which could be plausibly exhibited by the opponents of the theory during those fifteen years were, for the most part, not removed by the "Origin of Species," nor for a number of years subsequent to its publication. Substantially, whatever force the arguments for the transformist conception of the origin of the specific characters of organisms had after 1859, they had before; and whatever weaknesses they had before that memorable year, they still had after it. In presenting proof of this I shall, as before, indicate by direct citations the manner in which the arguments were used by the early Darwinians, and then point out the parallel reasonings in the evolutionists of the earlier period.
5. The Argument from the Sequence of Types in Paleontology.—The nature of this argument is, of course, too familiar to need exposition. The value which Huxley attached to it in 1863 is shown by a passage in his "Lectures on the Phenomena of Organic Nature ":
Just so did Chambers argue in his "Explanations," 1846:
Thus the general fact of the gradual appearance of higher types in the course of geological time, and the existence of a broad parallelism between antiquity of strata and relative simplicity of the contained organic forms, was by this time thoroughly established and universally familiar. True it is, however, that the evidence from paleontology, when more minutely scrutinized, proved to be by no means so favorable to the development hypothesis. This was so far the case that the orthodox geologists were able, with some real plausibility, to turn this weapon against the evolutionists. One of the only two really serious reasons that could be advanced after 1840 for rejecting the hypothesis lay in the observation that the facts of stratigraphic geology, as then known, failed to exhibit, with any consistency,or precision, the sequences that the hypothesis required. The principal fighting, between the time of the "Vestiges" and that of the "Origin," took place around this issue; and the battle-ground was well chosen for the conservatives. For the weakest side of the theory of development then was its paleontological side. But this continued to be its weakest side in the 1860's; and it is a side not wholly without weak points even at the present day, especially when to the theory of development is added the theory of natural selection.
The chief objections raised by the paleontologists were five in number. There was, first, the general difficulty about the "missing links" in the chain of past organisms. Secondly, there was the fact of the apparently sudden appearance of groups of allied, and by no means absolutely primordial, species in the lowest fossiliferous strata then known. Thirdly, there was the sudden disappearance of whole groups of species at the end of certain geological periods, and their sudden replacement in the next period by species different in type from the former, and closely allied to one another. These two points—the second and third—were the especial contribution of the Cuvierian school to the controversy. Out of Cuvier's doctrine of the abrupt extinction of faunas at the successive "revolutions of the globe," his disciples had elaborated the theory of the radical and world-wide discontinuity of the faunas and floras of the successive great periods, and had hence inferred the actual necessity of assuming a definite number of special creations of fresh organic worlds en bloc. D'Orbigny knew exactly how many such creations there had been:
Fourthly—to continue the enumeration of the paleontological difficulties—it was objected that, especially within the limits of single great geological formations, the arrangement of fossils in the strata did not exhibit the required order of progression from lower to higher types, but sometimes even reversed that order. This was Sedgwick's principal point in his Edinburgh Review article, as it was that of Hugh Miller in his "Footprints of the Creator," 1849, the most widely circulated of the replies to the "Vestiges." Miller's argument may be summarized in his own words. The latest discoveries in the Silurian and Cambrian series, he declared, do not show the
The reason why, according to Miller, it does not, constitutes the fifth objection urged against evolutionism from the side of paleontology; "superposition," as Miller put it, "does not mean parental relation," any more than the presence of gradually accumulated vegetable and animal refuse in a farmer's ditch means that the creatures whose remains lie at the bottom of the ditch begot those whose remains are found higher up.
The last argument does not call, and never did call, for serious consideration; it is a begging of the precise question at issue, concealed by a specious but lame analogy. The other four arguments depended, with respect to their logical weight, upon the way in which they were applied. If it were assumed that the burden of offering specific proofs rested upon the transformationist, and that the paleontological evidence was put forward by him as a proof, the objections of the orthodox geologists were perfectly sound: the paleontological evidence was not clear nor complete—though it assuredly pointed toward the probability of the hypothesis. If, again, transformism were regarded as an hypothesis which implied the existence of certain geologic facts, then, also, the objections enumerated were pertinent—with one all-important and extremely obvious qualification: the implied facts in stratigraphic geology had not been verified—so far as inquiry into a record that will always and necessarily remain fragmentary had then extended. If, lastly, the objections were advanced as a positive disproof of the transformation of species, they were entirely incompetent, by reason of the necessity of adding the qualification last mentioned. The record being notoriously incomplete, it was impossible to infer from mere breaches of continuity, and from an occasional failure in the general parallelism of geological antiquity with simplicity of organic type, that the order of appearance of species had not in fact been progressive, and the result of gradual modification through natural descent. The difficulties raised by the conservative paleontologists logically justified, at the utmost, only a Scotch verdict of "not proven"—so far as this part of the testimony is concerned.
This continued to be the logical situation in 1859 and for a number of years thereafter. Darwin wrote to Quatrefages:
That the objection from the general absence of intermediate links between species was a pertinent one he acknowledged with characteristic candor.
He recognized that, so far as geological knowledge then went, whole groups of species sometimes seemed to make their appearance abruptly; though he argued that the increase of such knowledge had steadily tended to diminish this semblance of abruptness. Wholly eliminated these sharp transitions have never been, to this day; the latest authoritative expositor of the general results of paleontology says of d'Orbigny that, though "his ideas" were "too absolute, his observations remain none the less exact in their broad lines, and the sudden replacing of marine faunas, when passing from one stage to another, or even from zone to zone, must be considered almost a general rule." The same writer, who is, of course, a convinced evolutionist, observes:
The second argument of the paleontological opponents of the theory Darwin regarded as still more deserving of serious consideration.
To all these objections, as to that drawn from the absence of a uniformly progressive sequence in the superposition of species of certain classes, Darwin opposed a single reply: "the imperfection of the geological record"—an imperfection due not only to the inadequacy of geological exploration but to the inevitable absence of many chapters from the rock-history itself. Paleontology thus offered to neither side materials for a decisive proof of its case. Darwin's ninth chapter presented these considerations in a masterly manner. But there was no time in the history of paleontology when they were not extremely obvious and familiar considerations. Chambers, in replying to his critics, had fallen back upon the argument from the inconclusiveness of negative evidence. Even Hugh Miller, without greatly profiting by his own precept, had pointed out "how unsafe it is for the geologist to base positive conclusions on merely negative data." And Spencer, in a brilliant article written in 1858, and published in the Universal Review in July, 1859, had urged that "along with continuity of life on the earth's surface, there not only may be, but must be, great gaps in the series of fossils;" and that "hence these gaps are no evidence against the doctrine of evolution." He concluded:
It must be admitted that the facts of Palaeontology can never suffice either to prove or disprove the Development Hypothesis; but that the most they can do is, to show whether the last few pages of the Earth's biologic history are or are not in harmony with this hypothesis.
In its later development, it is true, paleontology has been able to produce some striking supplementary evidences of evolution. In a limited number of cases, approximately complete and closely graduated series of forms of single orders or families can be exhibited in due stratigraphic superposition. But all the elaborate and impressive "form-series" have been worked out since 1859. Darwin himself made no original discoveries in this field; and as late as the sixth edition of the "Origin" the best evidence of the sort he presented from other writers is, I believe, summed up in these two sentences:
Several cases are on record of the same species presenting varieties in the upper and lower parts of the same formation. Thus Trautschold gives a number of instances with Ammonites, and Hilgendorf has described a most curious case of ten graduated forms of Planorbis multiformis in the successive beds of a fresh-water formation in Switzerland.
Of the two instances cited the first is vague—the great studies of Waagen (1869) and of Neumayr (1871-5) in the Ammonites were still to come; and the observations of Hilgendorf seem already, by the time the sixth edition of the "Origin" was prepared for the press, to have been shown to be erroneous. The best known example, to English readers, of a form-series is that of the Equidæ. But Rütimeyer's "Beiträge zur Kenntnis der fossilen Pferde" appeared only in 1863; and Huxley's researches in this field, which were the consequence, not the cause, of his acceptance of the theory of descent, were first presented to the public in his presidential address before the Geological Society in 1870.
6. The Argument from Persistent Types.—If good cases of graduated form-series were not available at the time of the "Origin" or before, the evolutionist of the period could still find in paleontology one sort of evidence decidedly unfavorable to the chief hypothesis then opposed to his own—that of extensive "revolutions of the globe," wholesale obliterations of faunas, and thorough-going new creations of the entire organic world. This evidence lay in the persistence of many orders and certain species through more than one geological epoch. The classic of the special creation doctrine was the introduction to the third edition of Cuvier's "Récherches sur les ossements fossiles"; and the principal argument of that work was, in the words of one of Cuvier's disciples, to the effect that "no fossil species, at least among the two classes of mammalia and reptilia, has any analogue among living species, or, in other words, that every fossil species is extinct," If this could be shown by positive evidence not to be the case, one of the principal supports of the special creation hypothesis was taken away from it. Huxley made much of this line of attack in a paper of 1859 and in his address before the Geological Society in 1862. He pointed out, for example, that lingula and certain mollusca "have persisted from the Silurian epoch to the present day, with so little change that competent malacologists are sometimes puzzled to distinguish the ancient from the modern species." He noted that the "group of crocodilia was represented at the beginning of the Mesozoic age, if not earlier, by species identical in the character of their organization with those now living"; and that, probably, even certain types of the ancient mammalian fauna, such as that of the marsupialia, have persisted with no greater change throughout as vast a lapse of time."
But the argument Huxley here used had not newly become available. Cuvier's generalization had gone far beyond any evidence which he had offered, or which could, in the nature of the case, be offered. The proposition was, indeed, insusceptible of proof, save by a sort of reasoning in a circle. For when the special creationists denied the survival of species from one epoch to another, they were using the word "species" in a sense different from that in which they, at least, usually employed it. In their zoology, the final test of specific difference between two forms was the sterility of the hybrid. But extinct forms can not be subjected to this test. In paleontology, therefore, differences of species had to be determined solely on grounds of morphological dissimilarity; while it was, at the same time, recognized that in living animals an immense range of such dissimilarity might be consistent with identity of physiological species. If the pug dog and the greyhound had been extinct, it is at least questionable whether paleontologists would have assigned them to the same species—especially if their remains had been found at different geological horizons. Under such circumstances, it was open to the paleontologist to multiply species almost ad libitum; if he had adopted a theory which required that no species found in one stratum should be found in another, it was easy to make the most of slight variations of form. Differentiations of species thus made, however, were essentially subjective; all that could conceivably have been proven objectively was that no form remained the same through successive geological periods. Yet even of this no proof was forthcoming; the geologic record was not the sort of document that could furnish proof for a universal negative. It furnished, in fact, evidence on the other side. Even Cuvier's eulogist had been obliged (1841) to limit the generalization by adding "at least among mammals and reptiles"—and then to make further exception of two orders of mammals. And Hitchcock in his "The Religion of Geology" (1852), while exaggerating the discontinuity of then known types, could say no more than that, "of the thirty thousand species of animals and plants found in the rocks, very few living species can be detected." But a few were as good as a multitude as witnesses to the fact that there had been no such complete, simultaneous extinctions of faunas, and radical alterations of terrestrial conditions, as the Cuvierian theory supposed. And we find Chambers, in 1844, citing specific examples of persistency, as Huxley was to do fifteen years later.
There is a badger of the Miocene which can not be distinguished from the badger of the present day. Our existing Meles taxus is therefore acknowledged by Mr. Owen to be "the oldest known species of mammal on the face of the earth." It is in like manner impossible to discover any difference between the existing wild cat and that which lived in the bone caves with the hyæna, rhinoceros and tiger of the ante-drift era, all of which are said to be extinct species. . . . There is a persistency of certain shells since the beginning of the tertiaries. . . . Several shells of the secondary formation straggling into the tertiaries are not less conclusive, in rigid reasoning, that all the tertiary species were descended from the secondary, though the wide unrepresented interval at that point allowed a greater transition of forms. In short, the whole of the divisions constructed by geologists upon the supposition of extensive introductions of totally new vehicles of life must give way before the application of this rule, and it must be seen that what they call new species are but variations of the old.
7. The Argument from the Recapitulation Theory.—In charging Chambers with prematurity in his acceptance of evolutionism, Professor Le Conte urged that "the foundation, the only solid foundation, of a true theory of evolution" is to be had solely in "the method of comparison of the phylogenic and the embryonic succession" and in the resultant principle that "the laws of embryonic development (ontogeny) are also the laws of geologic succession." This method and this principle Le Conte represented as "added" to biology by Agassiz. Holding such views of the importance and the date of origin of the recapitulation theory, Le Conte concluded that no one was reasonably entitled to believe in the transformation of species prior to the publication of the work of Agassiz; and hence that Chambers's evolutionism was a "baseless speculation." Le Conte's popular book has done much to form current ideas on this subject. But its author was misled by piety towards the memory of his greatest teacher into a serious neglect of chronology, in a matter where chronology is of the essence of the question at issue. Even if Agassiz be regarded as the originator of the doctrine of recapitulation, it must be remembered that he announced his evidences for that doctrine in his "Poissons du vieux grès rouge," 1842-44, and repeated them in popular form in his Lowell Lectures of 1848. And in point of fact, the doctrine and an important mass of evidence for it had then long been familiar; so that one finds Lyell, before 1835, arguing against the use of it as a proof of evolution. In the "Principles of Geology," he wrote:
Lyell's reply to this argument was brief and dogmatic: he fully admitted the facts, but denied the inference.
To the mind of Darwin the same sort of data presented a very different import.
Yet poor Chambers is reproached for "baseless speculation" because, looking upon facts accepted by all the competent embryologists of his time, he saw in them the meaning that Darwin afterwards saw, and that so great a mind as LyelPs had been unable to see. In the third edition of the "Vestiges," 1845, he wrote:
And in this Chambers found one of his chief evidences of transformation of species. Elsewhere in this edition he devotes several pages to the elaboration of the argument from recapitulation in the case of the brain. "Taking as a basis the scale of animated nature as presented in Dr. Fletcher's 'Rudiments of Physiology,'" he points out "the wonderful parity observed in the progress of creation, as presented to our observation in the succession of fossils, and also in the fœtal progress of one of the principal human organs."
8. The Argument from Rudimentary Organs.—In his "Lectures on the Phenomena of Organic Nature," 1863, Huxley mentions as illustrations of this type of evidence the fœtal teeth of the whalebone whale, the rudimentary toes in the horse's leg, the rudimentary teeth in the upper jaw of the calf. He concludes:
But from the same facts Chambers had argued to the same conclusion nearly a score of years earlier.
It is worth while, perhaps, before concluding, to bring the last six arguments together, in a single general view of their logical bearings. No one of them, nor all of them collectively, ever amounted to more than "circumstantial evidence" of the transformation of species; none of them actually exhibits any species in flagrante delicto of transmutation. These arguments got their force from the fact that, when taken together, they fitted with striking nicety into the requirements of one of the two possible hypotheses about the origin of species—a hypothesis already recommended on general grounds of scientific method; while they reduced the rival hypothesis to a grotesque absurdity. "Conceivable" that other hypothesis still remained, as Huxley contended. It was, and is, possible, by making a sufficient number of supplementary suppositions, to give to the special creation doctrine a form in which it is neither explicitly self-contradictory nor explicitly in conflict with any fact established by pure induction. But when thus fitted out with the epicycles required by the facts already known to the science of 1840, the doctrine certainly presented a singularly odd and whimsical appearance. It implied that the Creator had produced the different types of organisms by fits and starts, strewing them at irregular intervals along the vast reaches of geologic time. Precisely what happened on one of these interesting occasions, the hypothesis left in a baffling obscurity; after a somewhat extensive reading in the literature of the period, I can not recall that any special creationist replied to Spencer's request for particulars on this point. Spencer wrote in 1852:
On these matters the theory remained judiciously non-committal. But it maintained, at all events, that the vast majority of species, however created, were destined to be in turn destroyed—and destroyed by the operation of natural forces. The Great Artificer could fashion, but he was either unable or unwilling to protect, the creatures his imagination had devised. When ordinary physical processes were too much for them, sweeping them off by groups, or even, according to the favorite variant of the theory, obliterating them altogether, he was obliged to start afresh; whether this happened four or twelve or twenty-seven or thirty thousand times was a detail about which the partisans of the doctrine could not agree. The forms thus later produced did not always differ markedly for the better from their unfortunate precursors; many primitive and rather unsuccessful models continued to be repeated. But in general, as time went on, the Creator brought both more diverse and more complicated beings into existence. In doing so, he behaved after the manner of a lazy and incompetent architect, who, instead of "studying" each problem afresh, with reference to the special uses and situation of the edifice to be erected, is content to make a few minor alterations in a single conventionalized plan. The "unity of type" of organisms destined to the most dissimilar modes of existence was generally dilated upon with devout enthusiasm by the special creationists. They seem to have regarded it as an agreeable mannerism of the Creator's personal style. But it is the kind of mannerism which, in a human designer, is commonly ascribed to indolence or limited intelligence. Indeed, the parallel of the lazy architect was inadequate to represent the whole singularity of the Creator's mode of construction. He not only used as few general models as possible, but he also—when, with a cleared field, he created a fresh group of organisms—reproduced in them organs and members which had been functional and useful in their predecessors, but were with the new species useless, meaningless, and even disadvantageous—like the proverbial Chinese tailor, who laboriously imitates all the rents and stains in the discarded European garment given him as a model. Finally, the Creator was supposed to have implanted in all organisms the senseless habit of mimicking, in the embryonic stages of the individual's development, the forms of other and extinct organisms to which that individual bore no relation of kinship.
Such—with the details absolutely required by the accepted scientific knowledge of the time—was the hypothesis tenaciously held by most men of science for at least twenty years before 1859. With the greater number of them the motives for holding it were primarily theological; yet the thing that now impresses us in the theory is its extraordinarily irreligious, not to say blasphemous, character. Science might conceivably, after some fashion, have made shift with a hypothesis of this kind; but it is hard to see how any one could suppose it in any degree advantageous to religion. It had not even the poor merit of being anthropomorphic. For no man out of a madhouse ever behaved in such a manner as that in which, by this hypothesis, the Creator of the universe was supposed to have behaved. Ascribing to him both the ability and the disposition to intervene with absolute freedom in natural—or, at least, in organic—phenomena, the theory also represented him as incapable of intervening intelligently or effectually.
That men of great abilities were unable to see the true character of the hypothesis which great numbers of them so long embraced, is certainly an interesting, if not an encouraging, fact in the history of the human intellect. But the capacity of theological prepossessions and religious feeling to retard and confuse intellectual processes is an old story. More remarkable, perhaps, is the failure, for an equally long period, of a number of men not impeded by theological prepossessions—men who were capable of seeing the absurdities of the special creation hypothesis—to recognize the methodological superiority and the promise of scientific fruitfulness inhering in the other hypothesis, or even to recognize the logical obligation to choose between the only two hypotheses available. Men of science of the present generation have perhaps little to learn from a consideration of the reasons which prevented a Cuvier, a Miller, a Sedgwick or an Agassiz from accepting the theory of evolution. But there may still be for us profitable matter for reflection in a consideration of the reasons which prevented a Huxley from finding, in 1846, anything of value in facts and reasonings which thirteen years later he was, with unequalled vigor and skill, proclaiming from the housetops.
The only historian of English thought known to me who has quite truly stated what I believe to be the fact about this episode in the history of scientific opinion, is Mr. A. W. Benn. In his "Modern England " he observes concerning the "Vestiges":
The truth of this is, I think, by no means sufficiently recognized by biologists or by historians of science. I hope that the present study may somewhat contribute to the more general acknowledgment of the correctness of Mr. Benn's statement.
- Op. cit., p. 21.
- Op. cit., p. 106.
- D'Orbigny, "Cours élémentaire de Paléontologie Stratigraphique," 1849, II., 251; cited in Depéret, "The Transformations of the Animal World," 1909, pp. 18-19.
- Quoted from the American edition, 27th thousand, 1875, pp. 227-8; the edition has a eulogistic preface by Agassiz, 1851.
- Depéret, "The Transformations of the Animal World," 1909, p. 22; the following passage, p. 113.
- Citations are from "Origin of Species," sixth edition, ch. X., passim; this was ch. IX. of the first edition.
- "Footsteps of the Creator," p. 32.
- "Life and Letters of Herbert Spencer," II., 332.
- Reprinted in "Illustrations of Universal Progress," 1868, pp. 361, 376.
- Cf. O. Schmidt, "Descent and Darwinism," 1873, English tr., 1896, p. 96.
- Flourens, "Analyse raisonée des travaux de G. Cuvier," 1841.
- It was, indeed, possible to restate the special creation theory so as to avoid this difficulty; extinctions and fresh productions of species, one at a time, might be supposed to have taken place continuously, without any general or widespread "revolutions of the globe." Such a conception was put forward by Bronn in 1857. But when thus amended the theory was pretty manifestly in a state of hopeless overstrain. It now made miraculous interpositions a matter of, so to say, almost daily occurrence in the geologic history.
- "Explanations," 1846, p. 108 f.
- Le Conte, "Evolution in its Relation to Religious Thought," 2d ed., 1905, ch. II.: The Relation of Louis Agassiz to the Theory of Evolution.
- Cf. Agassiz's own words, cited in Marcou, "Louis Agassiz," I., 230; and Morgan, "Evolution and Adaptation," p. 61.
- First American edition, 1837, I., 526.
- "Origin of Species," sixth edition, ch. XIV.
- "Vestiges," third edition, 1845.
- "Vestiges" American (= third) edition, 1845, pp. 145-149. Chambers unluckily adds: "The land animals, we may be sure, have the rudiments of baleen in their organization."
- 1908, II., 307, I., 238.