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]
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.
Whenever the appearance of a so-called annectant type is antedated by that of the two forms, which it is supposed to connect, this fact is, naturally, a deathblow to its claim of being the “common ancestor,” even though, from a purely morphological standpoint, it should possess all the requisites of an ancestral type. Commenting upon the statement that a certain genus “is a truly annectant form uniting the Melocrinidae and the Platycrinidae,” Bather takes exception as follows: “The genus in question appeared, so far as we know, rather late in the Lower Carboniferous, whereas both Platycrinidae and Melocrinidae were already established in Middle Silurian time. How is it possible that the far later form should unite these two ancient families? Even a mésalliance is inconceivable.” (Science, Sept. 17, 1920, p. 260.)
Certainty, therefore, with respect to the comparative antiquity of the fossiliferous strata is the indispensable presupposition of any palæontological argument attempting to show that there is a gradual approximation of ancient, to modern, types. Yet, of all scientific methods of reckoning, none is less calculated to inspire confidence, none less safeguarded from the abuses of subjectivism and arbitrary interpretation, than that by which the relative age of the sedimentary rocks is determined!