3. Throughout the geological history there is progress toward greater complexity and higher grade, along with degradation and extinction. Though experience shows that it may be quite possible that new discoveries may enable us to trace some of the higher forms of life farther back than we now find them, yet there can be no question that in the progress of geological time lower types have given place to higher, less specialized to more specialized. Curiously enough, no evidence proves this more clearly than that which relates to the degradation of old forms. When, for example, the reptiles of the Mesozoic Age were the lords of creation, there was apparently no place for the larger Mammalia which appear at the close of the reptile dynasty. So in the Palæozoic, when trees of the cryptogamous type predominated, there seems to have been no room in nature for the forests of modern type which succeeded them. Thus the earth at every period was fully peopled with living beings—at first with low and generalized structures which attained their maxima at early stages and then declined, and afterward with higher forms which took the places of those that were passing away. These latter, again, though their dominion was taken from them, were continued in lower positions under the new dynasties. Thus none of the lower types of life introduced was finally abandoned, but, after culminating in the highest forms of which it was capable, each was still continued, though with fewer species and a lower place. Examples of this abound in the history of all the leading groups of animals and plants.
4. There is thus a continued plan and order in the history of life which cannot be fortuitous. The chance interaction of organisms and their environment, even if we assume the organisms and environment as given to us, could never produce an orderly continuous progress of the utmost complexity in its detail, and extending through an enormous lapse of time. It has been well said that if a pair of dice were to turn up aces a hundred times in succession, any reasonable spectator would conclude that they were loaded dice; so if countless millions of atoms and thousands of species, each including within itself most complex arrangement of parts, turn up in geological time in perfectly regular order and a continued gradation of progress, something more than chance must be implied. It is to be observed here that every species of animal or plant, of however low grade, consists of many co-ordinated parts in a condition of the nicest equilibrium. Any change occurring which produces unequal or disproportionate development, as the experience of breeders of abnormal varieties of animals and plants abundantly proves, imperils the continued existence of the species. Changes must, therefore, in order to be profitable, affect the parts of the organism simultaneously and symmetrically. The chances of this may well be compared to the casting of aces a hundred times in succession, and are so infinitely small as to be incredible under any other supposition than that of intelligent design.
Fig. 6.
Group of Plants (restored) from the Devonian period, illustrating the complexity and beauty of the earliest known land vegetation, though many of the leading forms of modern plants are unknown in this very ancient period.
5. The progress of life in geological time. Just as the growth of trees is promoted or arrested by the vicissitudes of summer and winter, so in the course of the geological history there have been periods of pause and acceleration in the work of advancement. This is in accordance with the general analogy of the operations of nature, and is in no way at variance with the doctrine of uniformity already referred to. Nor has it anything in common with the unfounded idea, at one time entertained, of successive periods of entire destruction and restoration of life. Prolific periods of this kind appear in the marine invertebrates of the early Cambrian, the plants (Figure 6) and fishes of the Devonian, the batrachians of the Carboniferous, the reptiles of the Trias, the broad-leaved trees of the Cretaceous, and the mammals of the early Tertiary. A remarkable contrast is afforded by the later Tertiary and modern time, in which, with the exception of man himself, and perhaps a very few other species, no new forms of life have been introduced, while many old forms have perished. This is somewhat unfortunate, since, in such a period of stagnation as that in which we live, we can scarcely hope to witness either the creation or the evolution of a new species. Evolutionists themselves—those, at least, who are willing to allow their theory to be at all modified by facts—now perceive this; and hence we have the doctrine, advanced by Mivart, Le Conte, and others, of "critical periods," or periods of rapid evolution alternating with others of greater quiescence. It is further to be observed here that in a limited way and with reference to certain forms of life we can see a reason for these intermittent creations. The greater part of the marine fossils known to us are from rocks now raised up in our continents, and they lived at periods when the continents were submerged. Now, in geological time these periods of submergence alternated with others of elevation; and it is manifest that each period of continental submergence gave scope for the introduction of numbers of new marine species, while each continental elevation, on the other hand, gave opportunity for the increase of land-life. Further, periods when a warm climate prevailed in the arctic regions—periods when plants such as now live in temperate regions could enjoy six months of continuous sunshine—were eminently favorable to the development of such plants, and were utilized for the introduction of new floras, which subsequently spread to the southward. Thus we see physical changes occurring in an orderly succession and made subservient to the progress of life.
6. There is no direct evidence that in the course of geological time one species has been gradually or suddenly changed into another. Of the latter we could scarcely expect to find any evidence in fossils; but of the former, if it had occurred, we might expect to find indications in the history of some of the numerous species which have been traced through successive geological formations. Species which thus continue for a great length of time usually present numerous varietal forms which have sometimes been described as new species; but when carefully scrutinized they are found to be merely local and temporary, and to pass into each other. On the other hand, we constantly find species replaced by others entirely new, and this without any transition. The two classes of facts are essentially different; and though it is possible to point out in the newer geological formations some genera and species allied to others which have preceded them, and to suppose that the later forms proceeded from the earlier, still, when the connecting-links cannot be found, this is mere supposition, not scientific certainty. Further, it proceeds on the principle of arbitrary choice of certain forms out of many without any evidence of genetic connection. The worthlessness of such derivation is well shown in a case which has often been paraded as an illustration of evolution—the supposed genealogy of the horse. In America a series of horse-like animals has been selected, beginning with the Orohippus of the Eocene, and these have been marshalled as the ancestors of the fossil horses of America; for there are no native horses in America in the modern period. Yet this is purely arbitrary, and dependent merely on a succession of genera more and more closely resembling the modern horse being procurable from successive Tertiary deposits, often widely separated in time and place. In Europe, on the other hand, the ancestry of the horse has been traced back to Palæotherium—an entirely different form—by just as likely indications. Both genealogies can scarcely be true, and there is no actual proof of either. The existing American horses, which are of European parentage, are, according to the theory, descendants of Palæotherium, not of Orohippus; but if we had not known this on historical evidence, there would have been nothing to prevent us from tracing them to the latter animal. This simple consideration alone is sufficient to show that such genealogies are not of the nature of scientific evidence.
It is further to be observed that some of the ablest palæontologists, and those who have enjoyed the largest opportunities of observation and comparison, attach no value whatever to theories of evolution as accounting for the origin of species. One of these is Joachim Barrande, the palæontologist of Bohemia, and the first authority in Europe on the fossils of the older formations. Barrande, like some other eminent palæontologists, has the misfortune to be an unbeliever in the modern gospel of evolution, but he has certainly labored to overcome his doubts with greater assiduity than even many of the apostles of the new doctrine; and if he is not convinced, the stubbornness of the facts he has had to deal with must bear the blame. In connection with his great and classical work on the Silurian fossils of Bohemia, it has been necessary for him to study the similar remains of every other country; and he has used this immense mass of material in preparing statistics of the population of the Palæozoic world more perfect than any other naturalist has been able to produce. In successive memoirs he has applied these statistical results to the elucidation of the history of the oldest group of crustaceans—the trilobites—and the highest group of the mollusks—the cephalopods. In his latest memoir of this kind he takes up the brachiopods, or lamp-shells, a group of bivalve shellfishes very ancient and very abundantly represented in all the older formations of every part of the world, and which thus affords the most ample material for tracing its evolution, with the least possible difficulty in the nature of "imperfection of the record."
Barrande, in the publication before us, discusses the brachiopods with reference, first, to the variations observed within the limits of the species, eliminating in this way mere synonyms and varieties mistaken for species. He also arrives at various important conclusions with reference to the origin of species and varietal forms, which apply to the cephalopods and trilobites as well as to the brachiopods, and some of which, as the writer has elsewhere shown, apply very generally to fossil animals and plants. One of these is that different contemporaneous species, living under the same conditions, exhibit very different degrees of vitality and variability. Another is the sudden appearance at certain horizons of a great number of species, each manifesting its complete specific characters. With very rare exceptions, also, varietal forms are contemporaneous with the normal form of their specific type, and occur in the same localities. Only in a very few cases do they survive it. This and the previous results, as well as the fact that parallel changes go on in groups having no direct reaction on each other, prove that variation is not a progressive influence, and that specific distinctions are not dependent on it, but on the "sovereign action of one and the same creative cause," as Barrande expresses it. These conclusions, it may be observed, are not arrived at by that "slap-dash" method of mere assertion so often followed on the other side of these questions, but by the most severe and painstaking induction, and with careful elaboration of a few apparent exceptions and doubtful cases.
His second heading relates to the distribution in time of the genera and species of brachiopods. This he illustrates with a series of elaborate tables, accompanied by explanation. He then proceeds to consider the animal population of each formation, in so far as brachiopods, cephalopods, and trilobites are concerned, with reference to the following questions: (1) How many species are continued from the previous formation unchanged? (2) How many may be regarded as modifications of previous species? (3) How many are migrants from other regions where they have been known to exist previously? (4) How many are absolutely new species? These questions are applied to each of fourteen successive formations included in the Silurian of Bohemia. The total number of species of brachiopods in these formations is six hundred and forty, giving an average of 45.71 to each, and the results of accurate study of each species in its characters, its varieties, its geographical and geological range, are expressed in the following short statement, which should somewhat astonish those gentlemen who are so fond of asserting that derivation is "demonstrated" by geological facts: