Cuvier and the Rise of Palæontology.
If this historical sketch had been prepared within a few years of the death of Cuvier, it would no doubt have held him up as the greatest of zoologists and comparative anatomists. Nor would it have been hard to find reasons for such a verdict. His Règne Animal extended and corrected the zoological system of Linnæus; his comparative anatomy, and especially his comparative osteology, were far ampler and more exact than anything that had been attempted before. It would not have been forgotten, moreover, that he was the practical founder of the new science of palæontology.
At a later time, say in the sixties and seventies of the nineteenth century, when the Origin of Species controversy was in full blast, any estimate of Cuvier by an evolutionist would have been much less laudatory. Cuvier had actively opposed that form of evolution which had been brought forward in his day, and with such power as to close the discussion for a time. The assailants of the Origin of Species found his refutation of unity of type and progressive development adaptable to the new situation, and the reasoning which had pulverised Geoffrey St. Hilaire was brought out again in order to pulverise Darwin. Then the supporters of Darwin found it necessary to show that Cuvier was by no means infallible. This they were able to do without introducing matter foreign to the main question, for Cuvier's exposition of fixity of species, of the principles of classification and of the process of extinction, were entirely opposed to the beliefs not only of Darwin, but of Lyell and the whole school which stood out for historical continuity, treated history of every kind as a process of development, extended almost without limit the duration of life on the earth, and enforced the obvious but neglected truth that results of any magnitude whatever may proceed from small causes operating through a sufficient length of time.
Darwin's main contentions are now accepted by the scientific world, and Cuvier's hostility to particular forms of evolution has become a mere historical episode of no lasting importance. Angry disputes concerning the weight of his authority are at an end; he is not to be blamed because thirty years after his death he was set up as judge of a cause which he had not heard. We are now ready to make fair allowance for the time in which his lot was cast—an age when geology, embryology, palæontology, and distribution were mere infants, some of them hardly yet born. We can also admit without reserve the incompetence of certain of Cuvier's antagonists, and justify the severity with which he treated unity of type as stated and defended by Geoffroy St. Hilaire. Now that the dust of controversy has settled, we are chiefly concerned to inquire: What of all Cuvier's work has proved to be really permanent? His zoology and his comparative anatomy have had to be completely re-cast, partly because of the new light thrown on them by embryology and the doctrine of descent with modification. His studies of extinct vertebrates, however, called into existence a new science, the science of Palæontology,[33] and it is mainly this which gives him a lasting and honoured place in the history of biology.
At the end of the eighteenth century it had been rather grudgingly admitted that some few animals were actually extinct. Buffon was able to quote as indubitable examples the mammoth and the mastodon. Their occurrence in countries unknown to the ancients, such as Siberia and North America, disposed of the explanation long clung to by the learned—viz., that their bones were the remains of elephants which had been led about by the Roman armies, while their large size and the ease with which they can be recognised rendered it highly improbable that they still survived anywhere on the surface of the globe.
It was therefore natural that Cuvier's first study in palæontology should relate to extinct elephants. He compared and distinguished several species, showed that they were distinct from the existing Asiatic and African species, a fact which had escaped the notice of Pallas, and argued from the well-known case of a Siberian mammoth preserved in ice and frozen mud with hardly any decomposition that it must have been overwhelmed by a sudden "revolution of the earth." Whatever we may think of Cuvier's geology, his comparisons of all known elephants, recent and fossil, introduced a new standard of exactness into these inquiries. From this beginning he went on to study all the extinct vertebrates which he could discover in public or private collections. By 1821 he had published elaborate and well-illustrated descriptions of near a hundred extinct animals, an extraordinary output for one investigator.
The most remarkable of his palæontological discoveries were made at home, in the lower tertiary rocks which underlie the city of Paris. He proved that in the valley of the Seine a large population of animals, all now extinct, had formerly flourished. None of these discoveries impressed his contemporaries more than the celebrated case of the fossil opossum. The bones were imbedded in a slab of gypsum, and were at first imperfectly exposed. The lower jaw, however, exhibited a peculiarity of marsupial or pouched animals, for its angle had an inwardly projecting shelf, not found in other quadrupeds. The opossums, like all marsupial animals, bear on the front of the pelvis two long bones, which support the pouch. These were as yet concealed, and Cuvier delayed clearing them until he had summoned friends, some of whom may have been sceptical about the possibility of reasoning with certainty from anatomical data. Warning them what to expect, he removed with a sharp tool the film of stone, and revealed the long and slender marsupial bones.[34] The ancient existence of marsupials in France was then a striking and almost incredible fact; increase of knowledge has not lessened its interest, though it has abated some of the wonder.
The fossil ungulates (hoofed quadrupeds) of the Paris basin taxed Cuvier's patience and skill to the utmost. In the tiresome work of piecing together a multitude of imperfect skeletons he set an example to all future palæontologists. That he drew general conclusions which we are unable to accept, and failed to draw conclusions which seem obvious to us, will surprise nobody whose reading has taught him how unprepared were the biologists of that age to handle great questions concerning the origin and extinction of races. Cuvier recognised among the fossils of the Paris quarries the bones of two genera of ungulates very different from any of recent times. One resembled the rhinoceros, tapir, and horse in being odd-toed; this he called Palæotherium. Another had the hind-foot even-toed, like a ruminant, though the fore-foot, with which he was imperfectly acquainted, showed points of resemblance to the other group. How cautiously he did his work may be gathered from the fact that he spent fifteen years upon the collection of facts before he attempted to restore these extinct forms, though almost every bone in their bodies had during that time passed through his hands.
The great interest of these fossil ungulates to the modern biologist is that they are relatively primitive types of the order. Palæotherium is not far from the ideal common ancestor of the rhinoceros, tapir, and horse; Anoplotherium not altogether unlike the ideal common ancestor of the hippopotamus, the swine, and the ruminants. It has been suspected that Cuvier was less obstinately devoted to the tenet of fixity of species than he was willing to admit in public. Whatever his private leanings may have been, he stood out resolutely for cogent proofs of transmutation. When it was contended that the Palæothere might have been the remote ancestor of existing ungulates, he demanded that the intermediate links should be produced. His demand could not be met till many years later, though intermediate forms between the Palæothere and the horse have since been furnished in abundance. Reserve about far-reaching deductions was surely wise at a time when plausible speculation was rife, and we ought not to judge Cuvier severely for having aspired to a rigour unattainable in a natural science, and certainly not always observed by himself. He hoped to see biology become as exact as astronomy. The hope may have been chimerical, but emphasis on this side was not altogether out of place in the generation of Geoffroy St. Hilaire and Oken.
If the great master who laid the foundations of palæontology could revisit the scene of his former labours, he would find that many strange things had happened since the appearance of his Ossemens Fossiles. He would perhaps be stupefied at first to discover how little is now made of the Revolutions of the Earth, the proofs of which had seemed to him unimpeachable, while the conjectures about the development of new races, which in his own day had been almost negligible, have proved to be anticipatory of fundamental biological truths. The first shock over, one can imagine the zest with which he would strive to combine the familiar facts into a body of new doctrine. The ungulates, recent and fossil, would of course interest him particularly. He would recognise the gradations of structure which run through the whole order, branching and crossing in all directions; gradation in the number of the toes, in the rearing of the body more and more upon the toe-tips, in the progressive complication of the teeth. One chain of examples would lead from the shallow, tuberculate molar of the pig to the molar of the horse or ruminant, deep and massive, with crescentic enamel-folds; another would illustrate the gradual development of tusks from ordinary incisors or canines; a third series would show the steps by which the primitive ungulate dentition became reduced to the dentition of the elephant, with only a single pair of incisors, enlarged into tusks several feet long, with no canines but molars of great weight, complicated by extreme folding. It would surprise and delight him to compare the almost insensible steps by which his own Palæothere can be seen to pass into the modern horse. Then we can imagine how our regenerate Cuvier would draw nearer and nearer to the common ancestor of the whole group, a five-toed, plantigrade ungulate, with the full dentition of forty-four unspecialised teeth, and how readily he would admit that Phenacodus, both in its structure and its geological horizon, was just the common ancestor that theory required. The proofs of intermediate stages between ancient and modern ungulates which he had once called for in vain, he would now find ready to his hand. It might well seem that the history of the ungulates, with all its modern expansions, would suffice to occupy even his unparalleled energy. He would see with delight how the palæontology which he had been the first to treat as a science has enlarged the comparative anatomy of which also he was so great a master. He would cheerfully admit that both yield proofs of that doctrine of descent with modification which a hundred years ago seemed to him so questionable.
From an engraved copy of the portrait by Pickersgill.
