In order to date the strata of any given series with reference to one another, the palæontologist starts with the principle that, in an undisturbed area, the deeper sediments have been deposited at an earlier period than the overlying strata. Such a criterion, however, is obviously restricted in its application to local areas, and is available only at regions of outcrop, where a vertical section of the strata is visibly exposed. To trace the physical continuity, however, of the strata (if such continuity there be) from one continent to another, or even across a single continent, is evidently out of the question. Hence, to correlate the sedimentary rocks of a given region with those of another region far distant from the former, some criterion other than stratigraphy is required. To supply this want, recourse has been had to index fossils, which have now come into general use as age-markers and means of stratigraphical correlation, where the criterion of superposition is either absent or inapplicable. Certain fossil types are assumed to be infallibly indicative of certain stratigraphical horizons. In fact, when it comes to a decision as to the priority or posteriority of a given geological formation, index fossils constitute the court of last appeal, and even the evidences of actual stratigraphical sequence and of physical texture itself are always discounted and explained away, whenever they chance to conflict with the presumption that certain fossil forms are typical of certain geological periods. If, for example, the superposed rock contains fossils alleged to be typical of an “earlier” stratigraphic horizon than that to which the fossils of the subjacent rock belong, the former is pronounced to be “older,” despite the fact that the actual stratigraphic order conveys the opposite impression. “We still regard fossils,” says J. W. Judd, “as the ‘medals of creation,’ and certain types of life we take to be as truly characteristic of definite periods as the coins which bear the image and superscription of a Roman emperor or of a Saxon king.” (Cf. Smithson. Inst. Rpt. for 1912, p. 356.) Thus it comes to pass, in the last analysis, that fossils, on the one hand, are dated according to the consecutive strata, in which they occur, and strata, on the other hand, are dated according to the fossils which they contain.
Such procedure, if not actually tantamount to a vicious circle, is, to say the least, in imminent danger of becoming so. For, even assuming the so-called empirical generalization, that makes certain fossils typical of certain definitely-aged geological “formations,” to be based upon induction sufficiently complete and analytic to insure certainty, at least, in the majority of instances, and taking it for granted that we are dealing with a case, where the actual evidence of stratigraphy is not in open conflict with that of the index fossils, who does not see that such a system of chronology lends itself only too readily to manipulation of the most arbitrary kind, whenever the pet preconceptions of the evolutionary chronologist are at stake? How, then, can we be sure, in a given case, that a verdict based exclusively on the “evidence” of index fossils will be reliably objective? It is to be expected that the evolutionist will refrain from the temptation to give himself the benefit of every doubt? Will there not be an almost irresistible tendency on the part of the convinced transformist to revise the age of any deposit, which happens to contain fossils that, according to his theory, ought not to occur at the time hitherto assigned?
The citation of a concrete example will serve to make our meaning clear. A series of fresh-water strata occur in India known as the Siwalik beds. The formation in question was originally classed as Miocene. Later on, however, as a result, presumably, of the embarrassing discovery of the genus Equus among the fossils of the Upper Siwalik beds, Wm. Blanford saw fit to mend matters by distinguishing the Upper, from the Lower, beds and assigning the former (which contain fossil horses) to the Pliocene period. The title Miocene being restricted by this ingenious step to beds destitute of equine remains, namely the Nahun, or Lower Siwalik, deposits, all danger of the horse proving to be older than his ancestors was happily averted. A mere shifting of the conventional labels, apparently, was amply sufficient to render groundless the fear, to which Professor A. Sedgwick had given expression in the following terms: “The genus Equus appears in the upper Siwalik beds, which have been ascribed to the Miocene age.... If Equus really existed in the Upper Miocene, it was antecedent to some of its supposed ancestors.” (“Students’ Textbook of Zoölogy,” p. 599.) Evidently, the Horse must reconcile himself perforce to the pedigree assigned to him by the American Museum of Natural History; for he is to be given but scant opportunity of escaping it. This classic genealogy has already entailed far too great an expenditure of time, money and erudition to permit of any reconsideration; and should it chance, in the ironic perversity of things, that the Horse has been so inconsiderate as to leave indubitable traces of himself in any formation earlier than the Pliocene, it goes without saying that the formation in question will at once be dated ahead, in order to secure for the “ancestors” that priority which is their due. An elastic criterion like the index fossil is admirably adapted for readjustments of this sort, and the evolutionist who uses it need never fear defeat. The game he plays can never be a losing one, because he gives no other terms than: Heads I win, tails you lose.
In setting forth the foregoing difficulties, we have purposely refrained from challenging the cardinal dogma of orthodox palæontology concerning the unimpeachable time-value of index fossils as age-markers. The force of these considerations, therefore, must be acknowledged even by the most fanatical adherents of the aforesaid dogma. Our forbearance in this instance, however, must not be construed as a confession that the dogma in question is really unassailable. On the contrary, not only is it not invulnerable, but there are many and weighty reasons for rejecting it lock, stock, and barrel.
The palæontological dogma, to which we refer, is reducible to the following tenets: (1) The earth is swathed with fossiliferous strata, in much the same fashion that an onion is covered with a succession of coats, and these strata are universal over the whole globe, occurring always in the same invariable order and characterized not by any peculiar uniformity of external appearance, physical texture, or mineral composition, but solely by peculiar groups of fossil types, which enable us to distinguish between strata of different ages and to correlate the strata of one continent with their counterparts in another continent—“Even the minuter divisions,” says Scott, “the substages and zones of the European Jura, are applicable to the classification of the South American beds.” (“Introduction to Geology,” p. 681.) (2) In determining the relative age of a given geological formation, its characteristic fossils form the exclusive basis of decision, and all other considerations, whether lithological or stratigraphic, are subordinated to this—“The character of the rocks,” says H. S. Williams, “their composition or their mineral contents have nothing to do with settling the question as to the particular system to which the new rocks belong. The fossils alone are the means of correlation.” (“Geological Biology,” pp. 37, 38.)
To those habituated to the common notion that stratigraphical sequence is the foremost consideration in deciding the comparative age of rocks, the following statement of Sir Archibald Geikie will come as a distinct shock: “We may even demonstrate,” he avers, “that in some mountainous ground the strata have been turned completely upside down, if we can show that the fossils in what are now the uppermost layers ought properly to lie underneath those in the beds below them.” (“Textbook,” ed. of 1903, p. 837.) In fact, the palæontologist, H. A. Nicholson, lays it down as a general principle that, wherever the physical evidence (founded on stratigraphy and lithology) is at variance with the biological evidence (founded on the presence of typical fossil organisms), the latter must prevail and the former must be ignored: “It may even be said,” he tells us, “that in any case where there should appear to be a clear and decisive discordance between the physical and the palæontological evidence as to the age of a given series of beds, it is the former that is to be distrusted rather than the latter.” (“Ancient Life History of the Earth,” p. 40.)
George McCready Price, Professor of Geology at a denominational college in Kansas, devotes more than fifty pages of his recent work, “The New Geology” (1923), to an intensely destructive criticism of this dogma of the supremacy of fossil evidence as a means of determining the relative age of strata. To cite Price as an “authority” would, of course, be futile. All orthodox geologists have long since anathematized him, and outlawed him from respectable geological society. Charles Schuchert of Yale refers to him as “a fundamentalist harboring a geological nightmare.” (Science, May 30, 1924, p. 487.) Arthur M. Miller of Kentucky University speaks of him as “the man who, while a member of no scientific body and absolutely unknown in scientific circles, has ... had the effrontery to style himself a ‘geologist.’” (Science, June 30, 1922, pp. 702, 703.) Miller, however, is just enough to admit that he is well-informed on his subject, and that he possesses the gift of persuasive presentation. “He shows,” says Miller, “a wide familiarity with geological literature, quoting largely from the most eminent authorities in this country and in Europe. Any one reading these writings of Price, which possess a certain charm of literary style, and indicate on the part of the author a gift of popular presentation which makes one regret that it had not been devoted to a more laudable purpose, must constantly marvel at the character of mind of the man who can so go into the literature of the subject and still continue to hold such preposterous opinions.” (Loc. cit., p. 702.)
In the present instance, however, our interest centers, not on the unimportant question of his official status in geological circles, but exclusively on the objective validity of his argument against the chronometric value of the index fossil. All citations, therefore, from his work will be supported, in the sequel, by collateral testimony from other authors of recognized standing. It is possible, of course, to inject irrelevant issues. Price, for example, follows Sir Henry Howorth in his endeavor to substitute an aqueous catastrophe for the glaciation of the Quaternary Ice Age, and he adduces many interesting facts to justify his preference for a deluge. But this is neither here nor there; for we are not concerned with the merits of his “new catastrophism.” It is his opportune revival in modern form of the forgotten, but extremely effective, objection raised by Huxley and Spencer against the alleged universality of synchronously deposited fossiliferous sediments, that constitutes our sole preoccupation here. It is Price’s merit to have shown that, in the light of recently discovered facts, such as “deceptive conformities” and “overthrusts,” this objection is far graver than it was when first formulated by the authors in question.
Mere snobbery and abuse is not a sufficient answer to a difficulty of this nature, and we regret that men, like Schuchert, have replied with more anger than logic. The orthodox geologist seems unnecessarily petulant, whenever he is called upon to verify or substantiate the foundational principles of lithic chronology. One frequently hears him make the excuse that “geology has its own peculiar method of proof.” To claim exemption, however, from the universal criterions of criticism and logic is a subterfuge wholly unworthy of a genuine science, and, if Price insists on discussing a subject, which the orthodox geologist prefers to suppress, it is the latter, and not the former, who is really reactionary.
Price begins by stating the issue in the form of a twofold question: (1) How can we be sure, with respect to a given fauna (or flora), say the Cambrian, that at one time it monopolized our globe to the complete exclusion of all other typical faunas (or floras), say the Devonian, or the Tertiary, of which it is assumed that they could not, by any stretch of imagination, have been contemporaneous, on either land or sea, with the aforesaid “older” fauna (or flora)? (2) Do the formations (rocks containing fossils) universally occur in such a rigidly invariable order of sequence with respect to one another, as to warrant our being sure of the starting-point in the time-scale, or to justify us in projecting any given local order of succession into distant localities, for purposes of chronological correlation?