Chapter III: Fossil Pedigrees (1)

“_By dint of such great efforts we succeeded only in piecing
together genial romances more or less historical._”—B. Grassi,
Prof. of Comparative Anatomy, Univ. of Rome, “La vita” (1906),
p. 227.

§ 1. =The Argument in the Abstract=

The palæontological argument for evolution is based upon the observed gradual approximation in type of the earlier forms of life, as represented by the fossils still preserved in successive geological strata, to the later forms of life, as represented by the contemporary species constituting our present flora and fauna. Here the observed distribution in time supplements and confirms the argument drawn from mere structural affinity. Here we are no longer dealing with the spatial gradation of contemporary forms, arranged on a basis of greater or lesser similarity (the gradation whence the zoölogist derives his argument for evolution), but with a temporal gradation, which is simultaneously a morphological series and an historical record. The lower sedimentary rocks contain specimens of organic life very unlike modern species, but, the higher we ascend in the geological strata, the more closely do the fossil forms resemble our present organisms. In fact, the closeness of resemblance is directly proportional to the proximity in time, and this seems to create a presumption that the later forms of life are the modified descendants of the earlier forms. Considered in the abstract, at least, such an argument is obviously more formidable than the purely anatomical argument based on the degrees of structural affinity observable in contemporary forms. It ought, therefore, to be extremely persuasive, provided, of course, it proceeds in rigorous accord with indubitably established facts and rules out relentlessly the alloy of uncritical assumptions.

Here, likewise, we find the theory of transformism asserting its superiority over the theory of immutability, on the ground that evolutionism can furnish a natural explanation for the gradational distribution of fossil types in the geological strata, whereas the theory of permanence resorts, it is said, to a supernaturalism of reiterated “new creations” alternating with “catastrophic exterminations.” Now, if this claim is valid, and it can be shown conclusively that fixism is inevitably committed to a postulate of superfluously numerous “creations,” then the latter theory is shorn of all right to consideration by Occam’s Razor: _Entia non sunt multiplicanda sine ratione._ It is rather difficult to conceive of the Creator as continually blotting out, and rewriting, the history of creation, as ruthlessly exterminating the organisms of one age, only to repopulate the earth subsequently with species differing but little from their extinct predecessors—_ad quid perditio haec_? Such procedure hardly comports with the continuity, regularity and irrevisable perfection to be expected in the works of that Divine Wisdom, which “reacheth ... from end to end mightily and disposeth all things sweetly” (_Wisdom_, viii; 1), which “ordereth all things in measure, and number and weight.” (_Wis._ xi; 21.)

Following the lead of other evolutionists, Wasmann has striven to saddle fixism with the fatuity of periodic catastrophism and “creation on the installment plan.” But even Cuvier, who is credited with having originated the theory of catastrophism, did not go to the absurd extreme of hypothecating reiterated creations, but sought to explain the repopulation of the earth after each catastrophe by means of migrations from distant regions unaffected by the catastrophe. Historically, too, fixism has had its uniformitarian, as well as its catastrophic, versions. In fact, Huxley classifies both uniformitarianism and catastrophism as fixistic systems, when he says: “I find three more or less contradictory systems of geologic thought ... standing side by side in Britain. I shall call one of them Catastrophism, another Uniformitarianism, the third Evolutionism.” (“Lay Sermons,” p. 229.) Obviously, then, fixism is separable from the hypothesis of repeated catastrophes alternating with repeated “creations.” Stated in proper terms, it is at one with evolutionism in rejecting as undemonstrated and improbable the postulate of reiterated cataclysms. It freely acknowledges that, in the absence of positive evidence of their occurrence, the presumption is against extraordinary events, like wholesale catastrophes. It sanctions the uniformitarian tenet that ordinary cosmic processes are to be preferred to exceptional ones as a basis of geological explanation, and it repudiates as unscientific any recourse to the unusual or the miraculous in accounting for natural phenomena. Its sole point of disagreement with evolutionism is its refusal to admit organic changes of _specific_ magnitude. It does, however, admit germinal changes of _varietal_ magnitude. It also recognizes that the external characters of the phenotype are the joint product of germinal factors and environmental stimuli, and admits, in consequence, the possibility of purely _somatic changes_ of considerable profundity being induced by widespread and persistent alterations in environmental conditions. Like Darwin, the uniformitarian fixist ascribes the origination of organic life to a single vivifying act on the part of the Creator, an act, however, that was _formative_ rather than _creative_, because the primal forms of life, whether few or many, were all evolved through Divine influence from preëxistent inorganic matter. Unlike Darwin, he ascribes the continuation of organic life to generative processes that were univocal (_generationes univocae_), and not gradually-equivocal (_generationes paulatim aequivocae_). In the next chapter, we shall see that, in attributing the initial formation of species to a Divine act, neither Darwin nor the creationists exposed themselves to the charge of explaining the “natural” by means of the “miraculous.” And, as for the process by which living forms were continued upon earth, the univocal reproductive process upheld by fixism is more manifestly a natural process than the gradually-equivocal generation of variable inheritance hypothecated by the theory of transmutation. The sole matter of dispute between the two views is whether the life-cycles of organisms are circles or spirals.

But all this, it will be said, is purely negative. Merely to refrain from any recourse to the extraordinary or the supernatural is by no means sufficient. “Natural explanations” must be explanatory as well as natural. Unless there be a simplification, a reduction of plurality to unity, a resolution of many particular problems into a common general problem, we have no explanation worthy of the name. Granting, therefore, that uniformitarian fixism does not recur to the anomalous or the miraculous, it still lies open to the charge of failing in its function as an explanation, because it multiplies origins in both space and time. Transformism, on the contrary, is said to elucidate matters, inasmuch as it unifies origins spatially and temporally.

That transformism successfully plausibleizes a unification of origins in space, is true only in a limited and relative sense. The most that can be said for the assumption, that resemblances rest on the principle of common inheritance, is that it permits of a numerical reduction of origins, but this numerical reduction will, by an intrinsic necessity, always fall short of absolute unification. The monophyletic derivation of all organic forms from one primordial cell or protoblast is a fantastic dream, for which, from the very nature of things, natural science does not, and can not, furnish even the semblance of an objective basis. The ground is cut from under our feet, the moment we attempt to extend the principle of descent outside the limits of an organic phylum. The sole basis of inference is a group of uniformities, and, unless these uniformities predominate over the diversities, there can be no rational application of the principle of transformism. Hence, the hypothesis, that organisms are consanguineous notwithstanding their differences, loses all value as a solution at the point where resemblances are outweighed by diversities. The transmutation assumed to have taken place must be never so complete as to have obliterated all recognizable vestiges of the common ancestral type. “Whenever,” says Driesch, “the theory that, in spite of their diversities, the organisms are related by blood, is to be really useful for explanation, it must necessarily be assumed in every case that the steps of change, which have led the specific form A to become the specific form B, have been such as only to change in part that original form A. That is to say: the similarities between A and B must never be overshadowed by their diversities.” (“Science and Philosophy of the Organism,” v. I, p. 254.) When, therefore, the reverse is true and diversities are prevalent over uniformities, we are left without clue or compass in the midst of a labyrinth of innumerable possibilities. Such are the limits imposed by the very nature of the evidence itself, and the scientists, who transgress these limits, by attempting to correlate the primary phyla, are on a par with those unconvincible geniuses, who continually besiege the Patent Office with schemes ever new and weird for realizing the chimera of “perpetual motion.”

Thus scientific transformism is unable to simplify the problem beyond a certain irreducible plurality of forms, lesser only in degree than the plurality postulated by fixism. This being the case, the attempts of Wasmann and Dorlodot to prune the works of Creation with Occam’s Razor are not only presumptuous, but precarious as well. _Qui nimis probat, nihil probat!_ If it be unworthy of God to multiply organic origins in space, then monophyletic descent is the only possible alternative, and polyphyletic transformism falls under the same condemnation as fixism. Yet the polyphyletic theory of descent is that to which both Wasmann and Dorlodot subscribe, as it is, likewise, the only kind of transformism which science can ever hope to plausibleize. Besides, too close a shave with Occam’s Razor would eliminate creation altogether, since all theologians cheerfully admit that it was the result of a free and unnecessary act on the part of God. When we apply our _rationes convenientiae_ to the Divine operations, we must not make the mistake of applying them to the Divine action itself instead of the created effects of that action. We may be competent to discern disorder and irregularity in finite things, but we are wholly incompetent to prescribe rules for Divine conduct. To say that God is constrained by His infinite Wisdom to indirect, rather than direct, production, or that He must evolve a variety of forms out of living, rather than non-living, matter, is to be guilty of ridiculous anthropomorphism. There is no _a priori_ reason, founded upon the Divine attributes, which restricts God’s creative action to the production of this, or that, number of primordial organisms, or which obliges him to endow primitive organisms with the power of transmutation.

But the fact that these _rationes convenientiae_ fail to establish the _a priori_ necessity of a unification of organic origins in space, does not imply that they are without value in suggesting the unification of organic origins in time. Order and regularity are not excluded by spatial multiplicity, but they may easily be excluded by the incongruities of an irregular succession of events. Indeterminism and chance are, indeed, inseparable from the course of Nature. There is in matter an unlimited potentiality, incommensurate with the limited efficacy of natural agencies. Hence it evades the absolute control of all finite factors and forces. But the anomalies and irregularities, which are contingent upon the limitation or frustration of second causes unable to impose an iron necessity upon evasive matter, are not referable to the First Cause, but rather to the finite efficacy of second causes. Such anomalies in natural processes, consequently, are not inconsistent with infinite wisdom and power on the part of the Creator. If, on the contrary, the anomaly occurs, not in the form of an accidental frustration of a natural agency, but in the form of an intrusive “new creation,” the irregularity in question would then be referable to the Creator Himself, and such derogations of order are inadmissible, except as manifestations of the supernatural. In fact, the abrupt and capricious insertion of a “new creation” into an order already constituted, say, for instance, the sudden introduction of Angiosperms in the Comanchian period, or of mammals in the Tertiary, would be out of harmony with both reason and revelation. Unless there is a positive reason for supposing the contrary, we must presume that, subsequent to the primordial constitution of things, the Divine influence upon the world has been concurrent rather than revolutionizing. Hence a theory of origins, compatible with the simultaneous “creation” of primal organisms, is decidedly preferable to a theory, which involves successive “creations” at random. That transformism dispenses with the need of assuming a succession of “creative” acts, is perfectly obvious, and, unless fixism can emulate its rival system in this respect, it cannot expect to receive serious attention.

But once fixism assumes the simultaneousness of organic origins, it encounters, in the absence of modern organic types from ancient geological strata, a new and formidable difficulty. Cuvier’s theory of numerous catastrophes followed by wholesale migrations of the forms, which had escaped extinction, is tantamount to an appeal to the extraordinary and the improbable for purposes of explanation, and this, as we have seen, is an expedient, which natural science is justified in refusing to sanction. Nor does the appeal to the incompleteness of the geological record offer a more satisfactory solution. It is tax enough, as we shall see, upon our credulity, when the transformist seeks to account thereby for the absence of intermediate types, but to account in this fashion for the absence of palæozoic Angiosperms and mammals is asking us to believe the all-but-incredible. It would not, therefore, be advisable for the fixist to appropriate the line of defense suggested for him by Bateson—“It has been asked how do you _know_ for instance that there were no mammals in Palæozoic times? May there not have been mammals somewhere on the earth though no vestige of them has come down to us? We may feel confident there were no mammals then, but are we sure? In very ancient rocks most of the great orders of animals are represented. The absence of the others might by no great stress of imagination be ascribed to accidental circumstances.” But the sudden rise of the Angiosperms in the early part of the Mesozoic era is an instance of _de novo_ origin that is not so easily explained away. Hence Bateson continues: “Happily, however, there is one example of which we can be sure. There were no Angiosperms—that is to say ‘higher plants’ with protected seeds—in the carboniferous epoch. Of that age we have abundant remains of a worldwide and rich flora. The Angiosperms are cosmopolitan. By their means of dispersal they must immediately have become so. Their remains are very readily preserved. If they had been in existence on the earth in carboniferous times they must have been present with the carboniferous plants, and must have been preserved with them. Hence we may be sure that they did appear on earth since those times. We are not certain, using certain in the strict sense, that Angiosperms are the lineal descendants of the carboniferous plants, but it is much easier to believe that they are than that they are not.” (_Science_, Jan. 20, 1922, p. 58.)

It would thus appear, that not all the organic types of either the plant, or the animal, kingdom are of equal antiquity, and that the belated rise of unprecedented forms has the status of an approximate certainty, wherewith every theory of origins must inevitably reckon. How, then, is the fixist to reconcile this successive appearance of organisms with the simultaneous “creation” advocated by St. Augustine and St. Thomas of Aquin? Unless there be some other gradual process besides transmutation, to bridge the interval between the creative fiat and the eventual appearance of modern types, there seems to be no escape from the dilemma.

This brings us to St. Augustine’s theory of the evolution of organic life from inorganic matter, which Dorlodot sophistically construes as supporting the theory of descent. According to St. Augustine, for whose view the Angelic Doctor expressed a deliberate preference, the creation of the corporeal world was the result of a single creative act, having an immediate effect in the case of minerals, and a remote or postponed effect in the case of plants and animals (cf. “De Genesi ad litteram,” lib. V, c. 5). Living beings, therefore, were created, not in actuality, but in germ. God imparted to the elements the power of producing the various plants and animals in their proper time and place. Hence living beings were created causally rather than formally, by the establishment of causal mechanisms or natural agencies especially ordained to bring about the initial formation of the ancestral forms of life. The Divine act initiating these “natural processes” (_rationes seminales, rationes causales_) in inorganic, and not in living, matter, was instantaneous, but the processes, which terminated in the formation of plants and animals, in their appointed time and place, were in themselves gradual and successive. Thus by an influx of Divine power the earth was made pregnant with the promise of every form of life—“_Sicut matres gravidae sunt foetibus, sic ipse mundus est gravidus causis nascentium._” (Augustine, lib. III, “de Trinitate,” c. 9.)

By reason of this doctrine, the Louvain professor claims that St. Augustine was an evolutionist, and so, indeed, he was, if by evolution is meant a gradual production of organisms from inorganic matter. But if, on the contrary, by evolution is meant a progressive differentiation and multiplication of organic species by transmutation of preëxistent forms of life, or, in other words, if evolution is taken in its usual sense as synonym for transformism, then nothing could be more absurdly anachronistic than to ascribe the doctrine to St. Augustine. The subject of the gradual process postulated by the latter was, not living, but _inorganic_, matter, and the process was conceived as leading to the _formation_, and not the transformation, of species. The idea of variable inheritance did not occur to St. Augustine, and he conceived organisms, once they were in existence, as being propagated exclusively by univocal reproduction (_generatio univoca_). It is the fixist, therefore, rather than the transformist, who is entitled to exploit the Augustinian hypothesis. In fact, it is only the vicious ambiguity and unlimited elasticity of the term evolution, which avail to extenuate the astounding confusion of ideas and total lack of historic sense, that can bracket together under a common term the ideology of Darwin and the view of St. Augustine.

§ 2. The Argument in the Concrete

But it is our task to criticize the theory of transformism, and not to throw a life-line to fixism, by advocating gradual formation of species as the only feasible alternative to gradual transformation of species. Perhaps, this particular life-line will not be appreciated any way; for the fixist may, not without reason, prefer to rest his case on the contention that the intrinsic _time-value_ of geological formations is far too problematic for certain conclusions of any sort. In maintaining this position, he will have the support of some present-day geologists, and can point, as we shall see, to facts that seem to bear out his contention. In fact, the cogency of the palæontological argument appears to be at its maximum in the abstract, and to evaporate the moment we carry it into the concrete. The lute seems perfect, until we begin to play thereon, and then we discover certain rifts that mar the effect. It is to these rifts that our attention must now be turned.

The first and most obvious flaw, in the evolutionary interpretation of fossil series, is the confounding of succession with filiation. Thinkers, from time immemorial, have commented on the deep chasm of distinction, which divides historical from causal sequence, and philosophers have never ceased to inveigh against the sophistical snare of: _Post hoc, ergo propter hoc._ That one form of life has been subsequent in time to another form of life is, in itself, no proof of descent. “Let us suppose,” says Bather, “all written records to be swept away, and an attempt made to reconstruct English history from coins. We could set out our monarchs in true order, and we might suspect that the throne was hereditary; but if on that assumption we were to make James I, the son of Elizabeth—well, but that’s just what palæontologists are constantly doing. The famous diagram of the Evolution of the Horse which Huxley used in his American lectures has had to be corrected in the light of the fuller evidence recently tabulated in a handsome volume by Prof. H. F. Osborn and his coadjutors. _Palæotherium_, which Huxley regarded as a direct ancestor of the horse, is now held to be only a collateral, as the last of the Tudors were collateral ancestors of the Stuarts. The later _Ancitherium_ must be eliminated from the true line as a side branch—a Young Pretender. Sometimes an apparent succession is due to immigration of a distant relative from some other region—‘The glorious House of Hanover and Protestant Succession.’ It was, you will remember, by such migrations that Cuvier explained the renewal of life when a previous fauna had become extinct. He admitted succession but not descent.” (_Science_, Sept. 17, 1920, p. 261.)

But, if succession does not imply descent, descent, at least, implies succession, and the fact that succession is the necessary corollary of descent, may be used as a corrective for the erroneous allocations made by neontologists on the basis of purely morphological considerations. The _priority_ of a type is the _sine qua non_ condition of its being accepted as _ancestral_. It is always embarrassing when, as sometimes happens, a “descendant” turns out to be older than, or even coëval with, his “ancestor.” If, however, the historical position of a form can be made to coincide with its anatomical pretensions to ancestry, then the inference of descent attains to a degree of logical respectability that is impossible in the case of purely zoölogical evidence. Recent years have witnessed a more drastic application of the historical test to morphological speculations, and the result has been a wholesale revision of former notions concerning phylogeny. “I could easily,” says Bather, “occupy the rest of this hour by discussing the profound changes wrought by this conception on our classification. It is not that orders and classes hitherto unknown have been discovered, not that some erroneous allocations have been corrected, but the whole basis of our system is being shifted. So long as we were dealing with a horizontal section across the tree of life—that is to say, with an assemblage of approximately contemporaneous forms—or even with a number of such horizontal sections, so long were we confined to simple description. Any attempt to frame a causal connection was bound to be speculative.” (_Ibidem_, p. 258.) Whether zoölogists will take kindly to this “shifting of the whole basis” of classification, remains to be seen. Personally, we think they would be very ill-advised to exchange the solid observational basis of homology for the scanty facts and fanciful interpretations of palæontologists.

The second stumbling block in the path of Transformism is the occurrence of convergence. We have seen that, in the palæontological argument, descent is inferred conjointly from similarity and succession, and that, in the abstract, this argument is very persuasive. One of the concrete phenomena, however, that tend to make it inconsequential, is the undoubted occurrence of convergence. Prof. H. Woods of Cambridge, in the Introduction to the 5th edition of his “Palæontology” (1919), speaks of three kinds of convergence (cf., pp. 14, 15, 16), which, as a matter of convenience, we may term the parallelistic, the radical, and the adaptational, types of convergence. A brief description of each type will serve to elucidate its nature and its significance:

(1) Parallelistic convergence implies the appearance of parallel modifications in the homologous parts of organisms regarded as diverging from common stock in two distinct collateral lines, that were independent at the time of the appearance in both of the said parallel modifications. Speaking of the fossil cœlenterates known as _Graptolites_, Professor Woods says: “In some genera the hydrothecæ of different species show great variety of form, those of one species being often much more like those of a species belonging to another genus than to other species of the same genus.” (“Palæontology,” 5th ed., 1919, p. 69.) As another instance of this phenomenon, the case of the fossil ungulates of South America, spoken of as _Litopterna_, may be cited, and the case is peculiarly interesting because of its bearing on that _pièce de résistance_ of palæontological evidence, the Pedigree of the Horse. “The second family of Litopterna,” says Wm. B. Scott, “the Proterotheriidæ, were remarkable for their many deceptive resemblances to horses. Even though those who contend that the Litopterna should be included in the Perissodactyla should prove to be in the right, there can be no doubt that the proterotheres were not closely related to the horses, but formed a most striking illustration of the independent acquisition of similar characters through parallel or convergent development. The family was not represented in the Pleistocene, having died out before that epoch, and the latest known members of it lived in the upper Pliocene.... Not that this remarkable character was due to grotesque proportions; on the contrary, they looked far more like the ordinary ungulates of the northern hemisphere than did any of their South American contemporaries; it is precisely this resemblance that is so notable.... The feet were three-toed, except in one genus (_Thoatherium_) in which they were single-toed, and nearly or quite the whole weight was carried upon the median digit, the laterals being mere dew-claws. The shape of the hoofs and the whole appearance of the foot was surprisingly like those of the three-toed horses, but there were certain structural differences of such great importance, in my judgment, as to forbid the reference of these animals, not merely to the horses, but even to the perissodactyls.” (“A History of Land Mammals in the Western Hemisphere,” p. 499.)

For this sort of parallelism, the Lamarckian and Darwinian types of evolution by addition can offer no rational explanation. It could, perhaps, be accounted for upon the Batesonian hypothesis of evolution by loss of inhibition, that is to say, the coincident appearance of convergent characters in collateral lines might be interpreted as being due to a parallel loss in both lines of the inhibitive genes, which had suppressed the convergent feature in the primitive or common stock. We say that the convergence _might_ be so interpreted, because the interpretation in question would, at best, be merely optional and not at all necessary; for in the third, or adaptational, type of convergence, we shall see instances of parallel modifications occurring in completely independent races, whose morphology and history alike exclude all possibility of hereditary connection between them. Hence, even in the present case, nothing constrains us to accept the genetic interpretation.

(2) Radical convergence, which Woods styles heterogenetic homœomorphy, is described by him as follows: “Sometimes two groups of individuals resemble each other so closely that they might be regarded as belonging to the same genus or even to _the same species_ (italics mine), but they have descended from different ancestors since they are found to differ in development (ontogeny) or in their palæontological history; this phenomenon, of forms belonging to different stocks approaching one another in character, is known as convergence or heterogenetic homœomorphy, and may occur at the same geological period or at widely separated intervals. Thus the form of oyster known as _Gryphaea_ has originated independently from oysters of the ordinary type in the Lias, in the Oölites, and again in the Chalk; these forms found at different horizons closely resemble one another and have usually been regarded as belonging to one genus (_Gryphaea_), but they have no direct genetic connection with one another.” (“Palæontology,” 5th ed., 1919, p. 15.) Comment is almost superfluous. If even _specific_ resemblance is no proof of common origin, then what right have we to interpret any resemblance whatever in this sense? With such an admission, the whole bottom drops out of the evolutionary argument. When the theory of descent is forced to account for heterogenetic resemblance at expense of all likelihood and consistency, when it cannot save itself except by blowing hot and cold with one breath, one is tempted to exclaim: “Oh, why bother with it!”

(3) Adaptational convergence is the occurrence of parallel modifications due to analogous specialization in unrelated forms, whose phylogeny has been obviously diverse. “Also, animals belonging to quite distinct groups,” says Woods, “may, when living under similar conditions, come to resemble one another owing to the development of adaptive modifications, though they do not really approach one another in essential characters; thus analogous or parallel modifications may occur in independent groups—such are the resemblances between flying reptiles (_Ornithosaurs_) and birds, and between sharks, icthyosaurs and dolphins.” (_Op. cit._, p. 16.) As this type of convergence has been discussed in a previous article, with reference to the mole and mole-cricket, it need not detain us further.

All these types of convergence, but especially the second type, are factual evidence of the compatibility of resemblance with independent origin, and the fact of their occurrence tends to undermine the certainty of the phylogenetic inferences based on fossil evidence; all the more so, that, thanks to its bad state of preservation, and the impossibility of dissection, even superficial resemblances may give rise to false interpretations. And, as for the cases of radical convergence, there is no denying that they strike at the very heart of the theory of descent.

The third difficulty for Transformism arises from the discontinuity of the geological record. It was one of the very first discrepancies to be discovered between evolutionary expectation and the actual results of research. The earliest explorations revealed a state of affairs, that subsequent investigations have failed to remedy: on the one hand, namely, a notable absence of intermediate species to bridge the gaps between the fossil genera, and on the other hand, the sudden and simultaneous appearance of numerous new and allied types unheralded by transitional forms. Since Darwin had stressed the gradualness of transmutation, the investigators expected to find the transitional means more numerous than the terminal extremes, and were surprised to find, in the real record of the past, the exact reverse of their anticipation. They found that the classes and families of animals and plants had always been as widely separated and as sharply differentiated as they are today, and that they had always formed distinct systems, unconnected by transitional links. The hypothetical “generalized types,” supposed to combine the features of two or three families, have never been found, and most probably never will be; for it is all but certain that they never existed. Occasionally, it is true, palæontologists have discovered isolated types, which they interpreted as annectant forms, but a single pier does not make a bridge, and only too often it chanced that the so-called annectant type, though satisfactory from the morphological standpoint, was more recent than the two groups, to which it was supposed to be ancestral. But it will make matters plainer, if we illustrate what is meant by the discontinuity or incompleteness of the fossil record, by reference to some concrete series, such as the so-called Pedigree of the Horse.

Whenever a series of fossils, arranged in the order of their historical sequence, exhibits a gradation of increasing resemblance to the latest form, with which the series terminates, such a series is called a palæontological pedigree, and is said to represent so many stages in the racial development or phylogeny of the respective modern type. The classical example of this sort of “pedigree” is that of the Horse. It is, perhaps, one of the most complete among fossil “genealogies,” and yet, as has been frequently pointed out, it is, as it stands, extremely incomplete. Modern representatives of the _Equidae_, namely, the horse, the ass and the zebra, belong to a common genus, and are separated from one another by differences which are merely specific, but the differences which separate the various forms, that compose the “pedigree of the Horse,” are generic. We have, to borrow Gerard’s simile, nothing more than the piers of the evolutionary bridge, without the arches, and we do not know whether there ever were any arches. There is, indeed, a sort of progression, _e.g._, from the four-toed to a one-toed type, so that the morphological gradation does, in some degree, coincide with temporal succession. But, on the other hand, the fossil forms, interpreted as stages in the phylogeny of the Horse, are separated from one another by gaps so enormous, that, in the absence of intermediate species to bridge the intervals, it is practically impossible, particularly in the light of our experimental knowledge of Genetics, to conceive of any transition between them. Nor is this all. The difficulty is increased tenfold, when we attempt to relate the _Equidae_ to other mammalian groups. Fossil ungulates appear suddenly and contemporaneously in the Tertiary of North America, South America and Europe, without any transitional precursors, to connect them with the hypothetical proto-mammalian stock, and to substantiate their collaterality with other mammalian stocks.

To all such difficulties the evolutionist replies by alleging the incompleteness of the geological record, and modern handbooks on palæontology devote many pages to the task of explaining why incompleteness of the fossil record is just what we should expect, especially in the case of terrestrial animals. The reasons which they assign are convincing, but this particular mode of solving the difficulty is a rather precarious one. Evolutionists should not forget that, in sacrificing the substantial completeness of the record to account for the absence of intermediate species, they are simultaneously destroying its value as a proof of the relative position of organic types in time. Yet this, as we have seen, is precisely the feature of greatest strategic value in the palæontological “evidence” for evolution. We must have absolute _certainty_ that the reputed “ancestor” was in existence prior to the appearance of the alleged “descendant,” or the peculiar force of the palæontological argument is lost. It would be preposterous for the progeny to be prior to, or even coëval with, the progenitor, and so we must be quite sure that what we call “posterity” is really posterior in time. Now the sole argument that palæontology can adduce for the posteriority of one organic type as compared with another is the negative evidence of its non-occurrence, or rather of its non-discovery, in an earlier geological formation. The lower strata do not, so far as is known, contain the type in question, and so it is concluded that this particular form had no earlier history. Such an inference, as is clear, is not only liable to be upset by later discoveries, but has the additional disadvantage of implicitly assuming the substantial completeness of the fossil record, whereas the absence of intermediate species is only explicable by means of the assumed incompleteness of the selfsame record. The evolutionist is thus placed in the dilemma of choosing between a substantially complete, and a substantially incomplete, record. Which of the alternatives, he elects, matters very little; but he must abide by the consequences of his decision, he cannot eat his cake and have it.

When the evolutionist appeals to the facts of palæontology, it goes without saying that he does so in the hope of showing that the differences, which divide modern species of plants and animals, diminish as we go backward in time, until the stage of identity is reached in the unity of a common ancestral type. Hence from the very nature of the argument, which he is engaged in constructing, he is compelled to resort to intermediate types as evidence of the continuity of allied species with the hypothetical ancestor, or common type, whence they are said to have diverged. Now, even supposing that his efforts in this direction were attended with a complete measure of success, evidence of this kind would not of itself, as we shall see, suffice to demonstrate the common origin of the extremes, between which a perfect series of intergradent types can be shown to mediate. Unquestionably, however, unless such a series of intergradent fossil species can be adduced as evidence of the assumed transition, the presumption is totally against the hypothesis of transformism.

Now, as a matter of fact, the geological record rarely offers any evidence of the existence in the past of intermediate species. For those, who have implicit confidence in the _time-value_ of geological “formations,” there are indications of a general advance from lower to higher forms, but, even so, there is little to show that this seeming progress is to be interpreted as an increasing divergence from common ancestral types. With but few exceptions, the fossil record fails to show any trace of transitional links. Yet pedigrees made up of diverse genera are poor evidence for filiation or genetic continuity, so long as no intermediate species can be found to bridge the chasm of generic difference. By intermediate species, we do not mean the fabulous “generalized type.” Annectants of this kind are mere abstractions, which have never existed, and never could have existed. We refer rather to actual fossil types separated from one another by differences not greater than specific; for “not until we have linked species into lineages,” can fossil pedigrees lay claim to serious attention.

But let us suppose the case for evolution to be ideally favorable, and assume that in every instance we possessed a perfect gradation of forms between two extremes, such, for example, as occurs in the Ammonite series, even then we would be far from having a true demonstration of the point at issue. Bateson has called our attention to the danger of confounding sterile and instable _hybrids_ with intergradent species. “Examine,” he says, “any two thoroughly distinct species which meet each other in their distribution, as for instance, _Lychnis diurna_ and _vespertina_ do. In areas of overlap are many intermediate forms. These used to be taken to be transitional steps, and the specific distinctness of _vespertina_ and _diurna_ was on that account questioned. Once it is known that these supposed intergrades are merely mongrels between the two species the transition from one to the other is practically beyond our powers of imagination to conceive. If both these can survive, why has their common parent perished? Why, when they cross, do they not reconstruct it instead of producing partially sterile hybrids? I take this example to show how entirely the facts were formerly misrepresented.” (_Heredity_, Smithson. Inst. Rpt. for 1915, p. 369.)

Similarly, T. H. Morgan has shown, with reference to _mutants_, the fallacy of inferring common descent from the phenomenon of intergradence, and what holds true for a series of intergradent mutants would presumably also hold true of a series of intergradent species, could such a series be found and critically distinguished from hybrid and mutational intermediates. In short, the Darwinian deduction of common origin from the existence of intergradence must now be regarded as a thoroughly discredited argument. “Because we can often arrange the series of structures in a line extending from the very simple to the more complex, we are apt to become unduly impressed by this fact and conclude that if we found the complete series we should find all the intermediate steps and that they have arisen in the order of their complexity. This conclusion is not necessarily correct.” (“A Critique of the Theory of Evolution,” p. 9.) Having cited such a series of gradational mutations ranging between the long-winged, and completely wingless condition, in the case of the Vinegar Fly (_Drosophila melanogaster_), as well as two similar graded series based on pigmentation and eye color, he concludes: “These types, with the fluctuations that occur within each type, furnish a complete series of gradations; yet historically they have arisen independently of each other. Many changes in eye color have appeared. As many as thirty or more races differing in eye color are now maintained in our cultures. Some of them are so similar that they can scarcely be separated from each other. It is easily possible beginning with the darkest eye color, sepia, which is a deep brown, to pick out a perfectly graded series ending with pure white eyes. But such a serial arrangement would give a totally false idea of the way the different types have arisen; and any conclusion based on the existence of such a series might very well be entirely erroneous, for the fact that such a series exists bears no relation to the order in which its members have appeared.” (_Op. cit._, pp. 12, 13.) Such facts must give us pause in attaching undue importance to phenomena like the occurrence of a gradual complication of sutures in the Chalk Ammonites, particularly as parallel series of perfectly similar sutures occurs “by convergence” in the fossil Ceratites, which have no genetic connection with the Ammonites. (Cf. Woods’ “Palæontology,” 5th ed., p. 16.)

But, if even mutational and specific intergradents are not sufficient evidence of common ancestry, what shall we say of a discontinuous series, whose links are separate genera, orders, or even classes, instead of species. Even the most enthusiastic transformist is forced to admit the justice of our insistence that the gaps which separate the members of a series must be reduced from differences of the generic, to differences of the specific, order, before that series can command any respect as hypothetical “genealogy.” “You will have observed,” says F. A. Bather, “that the precise methods of the modern palæontologist, on which this proof is based, are very different from the slap-dash conclusions of forty years ago. The discovery of _Archæopteryx_, for instance, was thought to prove the evolution of birds from reptiles. No doubt it rendered that conclusion extremely probable, especially if the major promise—that evolution was the method—were assumed. But the fact of evolution is precisely what men were then trying to prove. These jumpings from class to class or from era to era, by aid of a few isolated stepping-stones, were what Bacon calls anticipations “hasty and premature but very effective, because as they are collected from a few instances, and mostly from those which are of familiar occurrence, they immediately dazzle the intellect and fill the imagination.” (_Nov. Org._, I, 28.) No secure step was taken until the modern palæontologist began to affiliate mutation with mutation and species with species, working his way back, literally inch by inch, through a single small group of strata. Only thus could he base on the laboriously collected facts a single true interpretation; and to those who preferred the broad path of generality his interpretations seemed, as Bacon says they always “must seem, harsh and discordant—almost like mysteries of faith.” ... Thus by degrees we reject the old slippery stepping-stones that so often toppled us into the stream, and, foot by foot, we build a secure bridge over the waters of ignorance.” (_Science_, Sept. 17, 1920, pp. 263, 264.)

We cannot share Bather’s confidence in the security of a bridge composed of even linked species. Let such a series be never so perfect, let the gradation be never so minute, as it might conceivably be made, when not merely distinct species, but also hybrids, mutants and fluctuants are available as stopgaps, the bare fact of such intergradation tells nothing whatever concerning the problem of genetical origin and specific relationship. The species-by-species method does, however, represent the very minimum of requirement imposed upon the palæontologist, who professes to construct a fossil pedigree. But, when all is said and done, such a method, even at its best, falls considerably short of the mark. However perfectly intergradent a series of fossils may be, the fact remains that these petrified remnants of former life cannot be subjected to breeding tests, and that, in the consequent absence of genetical experimentation, we have no means of determining the real bearing of these facts upon the problem of interspecific relationship. Only the _somatic_ characters of extinct floras and faunas have been conserved in the rock record of the past, and even these are often rendered dubious, as we shall see presently, by their imperfect state of preservation. Now, it is solely in conjunction with breeding experiments, that somatic characters can give us any insight into the nature of the _germinal constitution_ of an organism, which, after all, is the cardinal consideration upon which the whole question of interspecific relationship hinges. All inferences, therefore, regarding the descent of fossil forms are irremediably speculative and conjectural. When we are dealing with living forms, we can always check up the inferences based on somatic characteristics by means of genetical experiments, and in so doing we have found that it is as unsafe to judge of an organism from the exclusive standpoint of its external characters as it is to judge of a book by the cover; for, apart from the check of breeding tests, it is impossible to say just which somatic characters are genetically significant, and which are not. Forms externally alike may be so unlike in germinal constitution as to be sexually incompatible; forms externally unlike may be readily crossed without any discernible diminution of fertility. “Who could have foreseen,” exclaims Bateson, “that the apple and the pear—so like each other that their botanical differences are evasive—could not be crossed together, though species of _Antirrhinum_ (Snapdragon) so totally unlike each other as _majus_ and _molle_ can be hybridized, as Baur has shown, without a sign of impaired fertility?” (_Heredity_, Smithson. Inst. Rpt. for 1915, p. 370.) We cannot distinguish between alleged specific, and merely mutational (varietal), change, nor between hybridizations and factorial, chromosomal, or pseudo-, mutations, solely on the basis of such external characters as are preserved for us in fossils. It is impossible, therefore, to demonstrate trans-specific variation by any evidence that Palæontology can supply. The palæontologist (_pace_ Osborn) is utterly incompetent to pass judgment on the problem of interspecific relationship. As Bateson remarks: “In discussing the physiological problem of interspecific relationship evidence of a more stringent character is now required; and a naturalist acquainted with genetical discoveries would be as reluctant to draw conclusions as to the specific relationship of a series of fossils as a chemist would be to pronounce on the nature of a series of unknown compounds from an inspection of them in a row of bottles.” (_Science_, April 17, 1922, p. 373.) “When the modern student of variation and heredity,” says T. H. Morgan, “looks over the different ‘continuous’ series, from which certain ‘laws’ and ‘principles’ have been deduced, he is struck by two facts: that the gaps, in some cases, are enormous as compared with the single changes with which he is familiar, and (what is more important) that they involve numerous parts in many ways. The geneticist says to the palæontologist, since you do not know, and from the nature of your case can never know, whether your differences are due to one change or to a thousand, you cannot with certainty tell us anything about the hereditary units which have made the process of evolution possible.” (_Op. cit._, pp. 26, 27.) And without accurate knowledge on this subject, we may add, there is no possibility of demonstrating specific change or genetic relationship in the case of any given fossil.

In our discussion of the third defect in the fossil “evidence,” allusion was made to a fourth, namely, its imperfect state of preservation. The stone record of bygone days has been so defaced by the metamorphism of rocks, by the solvent action of percolating waters, by erosion, weathering and other factors of destruction, that, like a faded manuscript, it becomes, even apart from its actual _lacunae_, exceedingly difficult to decipher. So unsatisfactory, indeed, is the condition of the partially obliterated facts that human curiosity, piqued at their baffling ambiguity, calls upon human imagination to supply what observation itself fails to reveal. Nor does the invitation remain unheeded. Romance hastens to the rescue of uncertain Science, with an impressive display of “reconstructed fossils,” and the hesitation of critical caution is superseded by the dogmatism of arbitrary assumption. Scattered fragments of fossilized bones are integrated into skeletons and clothed by the magic of creative fancy with an appropriate musculature and flesh, reënacting for us the marvelous vision of Ezekiel: “And the bones came together, each one to its joint. And I beheld and, lo, there were sinews upon them, and the flesh came upon them: and the skin was stretched over them.” (Chap. XXXVII, 7, 8.) “It is also true,” says Osborn (who, like Haeckel, evinces a veritable mania for “retouching” incomplete facts), “that we know the mode of origin of the human species; our knowledge of human evolution has reached a point not only where a number of links are thoroughly known but the characters of the missing links can be very clearly predicated.” (_Science_, Feb. 24, 1922.) We will not dispute his contention; for it is perfectly true, that, in each and every case, all the missing details can be so exactly predicated that the resulting description might well put to shame the account of a contemporary eyewitness. The only difficulty is that such predication is the fruit of pure imagination. Scientific reconstructions, whether in the literary, plastic, or pictorial, form, are no more scientific than historical novels are historical. Both are the outcome of a psychological weakness in the human makeup, namely, its craving for a “finished picture”—a craving, however, that is never gratified save at the expense of the fragmentary basis of objective fact.[7]

[7] See Addenda.

In calling into question, however, the scientific value of the so-called “scientific reconstruction,” so far as its pretensions to precision and finality are concerned, it is not our intention to discredit those tentative restorations based upon Cuvier’s Law of Correlation, provided they profess to be no more than provisional approximations. Many of the structural features of organisms are physiologically interdependent, and there is frequently a close correlation among organs and organ-systems, between which no causal connection or direct physiological dependence is demonstrable. In virtue of this principle, one structural feature may connote another, in which case it would be legitimate to supply by inference any missing structure implied in the actual existence of its respective correlative. But if any one imagines that the law of correlation enables a scientist to restore the lost integrity of fossil types with any considerable degree of accuracy and finality, he greatly overestimates the scope of the principle in question. At best it is nothing more than an empirical generalization, which must not be pressed to an extent unwarranted by the inductive process, that first established it. “Certain relations of structure,” says Bather, “as of cloven hoofs and horns with a ruminant stomach, were observed, but as Cuvier himself insisted, the laws based on such facts were purely empirical.” (_Science_, Sept. 17, 1920, p. 258.) The palæontologist, then, is justified in making use of correlation for the purpose of reconstructing a whole animal out of a few fragmentary remains, but to look for anything like photographic precision in such “restorations” of extinct forms is to manifest a more or less complete ignorance of the nature and scope of the empirical laws, upon which they are based.

The imprudence of taking these “reconstructions” of extinct forms too seriously, however, is inculcated not merely by theoretical considerations, but by experience as well. Even in the case of the mammoth, a comparatively recent form, whose skeletal remains had been preserved more completely and perfectly than those of other fossil types, the discovery of a complete carcass buried in the ice of the Siberian “taiga” on the Beresovka river showed the existing restorations to be false in important respects. All, without exception, stood in need of revision, proving, once and for all, the inadequacy of fossil remains as a basis for exact reconstruction. E. Pfizenmayer, a member of the investigating expedition, comments on the fact as follows: “In the light of our present knowledge of the mammoth, and especially of its exterior, the various existing attempts at a restoration need important corrections. Apart from the many fanciful sketches intended to portray the exterior of the animal, all the more carefully made restorations show the faults of the skeleton, hitherto regarded as typical, on which they are based, especially the powerful semicircular and upward-curved tusks, the long tail, etc.

“As these false conceptions of the exterior of the mammoth, both written and in the form of pictures, are contained in all zoölogical and palæontological textbooks, and even in scientific monographs, it seems necessary to construct a more nearly correct picture, based on our present knowledge. I have ventured on this task, because as a member of the latest expedition for mammoth remains, I was permitted not only to become acquainted with this newest find while still in its place of deposit and to take part in exhuming it, but also to visit the zoölogical museum of St. Petersburg, which is so rich in mammoth remains, for the purpose of studying the animal more in detail.” (Smithson. Inst. Rpt. for 1906, pp. 321, 322.) The example is but one of many, which serve to emphasize not merely the inadequacy of the generality of palæontological restorations, but also the extreme difficulty which the palæontologist experiences in interpreting aright the partially effaced record of a vanished past.

The fifth and most critical flaw in the fossil “evidence” for evolution is to be found in the anomalies of the actual distribution of fossils in time. It is the boast of evolutionary Palæontology that it is able to enhance the cogency of the argument from mere structural resemblance by showing, that, of two structurally allied forms, one is more ancient than the other, and may, therefore, be presumed to be ancestral to the later form. Antecedence in time is the _sine qua non_ qualification of a credible ancestor, and, unless the relative priority of certain organic types, as compared with others, can be established with absolute certainty, the whole palæontological argument collapses, and the boast of evolutionary geology becomes an empty vaunt.