Henry Fairfield Osborn

“ Thus the collective fauna of ancient South America mimics the independently evolved collective fauna of North America, the collective fauna of modern Australia mimics the collective fauna of the Lower Eocene of North America. ”

“ Vertebrates.—In discovery the theatre of interest has shifted from continent to continent, often in a sensational manner. After a long period of gradual revelation of the ancient life of Europe, extending eastward to Greece, eastern Asia and to Australia, attention became centred on North America, especially on Rocky Mountain exploration. New and unheard-of orders of amphibians, reptiles and mammals came to the surface of knowledge, revolutionizing thought, demonstrating the evolution theory, and solving some of the most important problems of descent. ”

“ Palaeontology both borrow's from and sheds light upon geology and other branches of the physical history of the earth, each of which, such as palaeogeography or palaeometeorology, is the more fascinating because of the large element of the unknown, the need for constructive imagination, the appeal to other branches of biological and physical investigation for supplementary evidence, and the necessity of constant comparison with the present aspects of nature. ”

“ A very important evolutionary principle is that in such secondary returns to primary phases lost organs are never recovered, but new organs are acquired; hence the force of Dollo's dictum that evolution is irreversible from the point of view of structure, while frequently reversible, or recurrent, in point of view of the conditions of environment and adaptation. ”

“ Geology and Palaeophysiography.—Fossils are not absolute timekeepers, because we have little idea of the rate of evolution; they are only relative timekeepers, which enable us to check off the period of deposition of one formation with that of another. Huxley questioned the time value of fossils, but recent research has tended to show that identity of species and of mutations is, on the whole, a guide to synchroneity, though the general range of vertebrate and invertebrate life as well as of plant life is generally necessary for the establishment of approximate synchronise. ”

“ The degree of accuracy in such anatomical and physiographic restorations from relatively imperfect evidence will always represent the state of the science and the degree of its approach toward being exact or complete. Progress in the science also depends upon the pursuit of palaeontology as zoology and not as geology, because it was a mere accident of birth which connected palaeontology so closely with geology. ”

“ The task of the palaeontologist thus begins with the appearance of life on the globe, and ends in close relation to the studies of the archaeologist and historian as well as of the zoologist and botanist. That wealth of evidence which the zoologist enjoys, including environment in all its aspects and anatomy in its perfection of organs and tissues, the palaeontologist finds partially or wholly destroyed, and his highest art is that of complete restoration of both the past forms and past environments of life (see Plates I. and II.; figs. 1, 2, 3, 4, 5) . ”

“ Adaptation and the Independent Evolution of Parts.—Step by step there have been established in palaeontology a number of laws relating to the evolution of the parts of animals which closely coincide with similar laws discovered by zoologists. All are contained in the broad generalization that every part of an animal, however minute, has its separate and independent basis in the hereditary substance of the germ cells from which it is derived and may enjoy consequently a separate and independent history. ”

“ The net result of observation is not favourable to the essentially Darwinian view that the adaptive arises out of the fortuitous by selection, but is rather favourable to the hypothesis of the existence of some quite unknown intrinsic law of life which we are at present totally unable to comprehend or even conceive. We have shown that the direct observation of the origin of new characters in palaeontology brings them within that domain of natural law and order to which the evolution of the physical universe conforms. ”

“ In the Jurassic period there were no less than six orders of reptiles which independently abandoned terrestrial life and acquired more or less perfect adaptation to sea life. Nature, limited in her resources for adaptation, fashioned so many of these animals in like form that we have learned only recently to distinguish similarities of analogous habit from the similitudes of real kinship. From whatever order of Mammalia or Reptilia an animal may be derived, prolonged aquatic adaptation will model its outer, and finally its inner, structure according to certain advantageous designs. ”

“ It is to palaeogeography and zoogeography in their reciprocal relations that palaeontology has rendered the most unique services. Geographers are practically helpless as historians, and problems of the former elevation and distribution of the land and sea masses depend for their solution chiefly upon the palaeontologist. With good reason geographers have given reluctant consent to some of the bold restorations of ancient continental outlines by palaeontologists; yet some of the greatest achievements of recent science have been in this field. ”

“ The treatise which laid the foundation for all subsequent invertebrate palaeontology was his memoir, Sur les fossiles des environs de Paris . . . (1802-1806) . Beginning in 1793 he boldly advocated evolution, and further elaborated five great principles—namely, the method of comparison of extinct and existing forms, the broad sequence of formations and succession of epochs, the correlation of geological horizons by means of fossils, the climatic or environmental changes as influencing the development of species, the inheritance of the bodily modifications caused by change of habit and habitat. ”

“ Embryology and Ontogeny.—In following the discovery of the law of recapitulation among palaeontologists we have clearly stated the chief contribution of palaeontology to the science of ontogeny—namely, the correspondences and differences between the individual order of development and the ancestral order of evolution. ”

“ Periods of Gradual Evolution of Groups.—It is certainly a very striking fact that wherever we have been able to trace genetic series, either of invertebrates or vertebrates, in closely sequent geological horizons, or life zones, we find strong proof of evolution through extremely gradual mutation simultaneously affecting many parts of each organism, as set forth above. ”

“ We observe the contemporaneous and largely independent radiations of the hoofed animals in South America, in Africa and in the great ancient continent comprising Europe, Asia and North America; we observe the Cretaceous radiation of hoofed animals in the northern hemisphere, followed by a second radiation of hoofed animals in the same region, in some cases one surviving spur of an old radiation becoming the centre of a new one. As a rule, the larger the geographic theatre the grander the radiation. ”

“ Great waves of extinction have followed the long periods of the slow evolution of relatively in adaptive types of tooth and foot structure, as first demonstrated by Waldemar Kowalevsky; thus mammals are repeatedly observed in a cul-de-sac of structure from which there is no escape in an adaptive direction. Among still other causes are great bulk, which proves fatal under certain new conditions; relatively slow breeding; extreme specialization and development of dominant organs, such as horns and tusks, on which for a time selection centres to the detriment of more useful characters. ”

“ Periods of Rapid Evolution of Groups.—The above law of gradual evolution is perfectly consistent with a second principle, namely, that at certain times evolution is much more rapid than at others, and that organisms are accelerated or retarded in development in a manner broadly analogous to the acceleration or retardation of separate organs. ”

“ In future the philosophic method of palaeontology must continue to advance step by step with exploration; it would be a reproach to later generations if they did not progress as far beyond the philosophic status of Cuvier, Owen and even of Huxley and Cope, as the new materials represent an advance upon the material opportunities which came to them through exploration. ”

“ Internal causes of extinction are to be found in exaggeration of body size, in the hypertrophy or over-specialization of certain organs, in the irreversibility of evolution, and possibly, although this has not been demonstrated, in a progressive reduction of variability. ”

“ Invertebrate palaeontology founded by Lamarck, vertebrate palaeontology by Cuvier. Palaeontology connected with comparative anatomy by Cuvier. Invertebrate fossils employed for the definite division of all the great periods of time.—Although pre-evolutionary, this was the heroic period of the science, extending from the close of the 18th century to the publication of Darwin's Origin of Species in 1859. Among the pioneers of this period were the vertebrate zoologists and comparative anatomists Peter Simon Pallas, Pieter Camper and Johann Friedrich Blumenbach. ”

“ In other words, the origin, or first appearance of new characters, which is the essence of evolution, is an orderly process so far as the vertebrate and invertebrate palaeontologist observes it. The selection of organisms through the crucial test of fitness and the shaping of the organic world is an orderly process when contemplated on a grand scale, but of another kind ”

“ Depéret points also that we owe to Cuvier the first clear expression of the idea of the increasing organic perfection of all forms of life from the lower to the higher horizons, and that, while he believed that extinctions were due to sudden revolutions on the surface of the earth, he also set forth the pregnant ideas that the renewals of animal life were by migration from other regions unknown, and that these migrations were favoured by alternate elevations and depressions which formed various land routes between great continents and islands. ”

“ It is equally true that palaeontological evidence has frequently failed where we most sorely needed it. The student must therefore resort to what may be called a tripod of evidence, derived from the available facts of embryology, comparative anatomy and palaeontology. ”

“ The Extinction of Groups.—We have seen that different lines vary in vitality and in longevity, that from the earliest times senescent branches are given off, that different lines vary in the rate of evolution, that extinction is often heralded by symptoms of racial old age, which, however, vary widely in different groups. In general we find an analogy between the development of groups and of organs ”

“ Among the ammonites the loss of power to coil the shell is one feature of racial old age, and in others old age is accompanied by closer coiling and loss of surface ornamentation, such as spines, ribs, spirals; while in other forms an arresting of variability precedes extinction. Thus Williams has observed that if we find a species breeding perfectly true we can conceive it to have reached the end of its racial life period. ”

“ It is true that a great variety of evidence is afforded by the composition of the rocks, that glaciers have left their traces in glacial scratchings and transported boulders, also that proofs of arid or semiarid conditions are found in the reddish colour of rocks in certain portions of the Palaeozoic, Trias and Eocene; but fossils afford the most precise and conclusive evidence as to the past history of climate, because of the fact that adaptations to temperature have remained constant for millions of years. ”

“ In brief, it must connect living distribution with distribution in past time, and develop a system which will be in harmony with the main facts of zoology and palaeontology. The theory of past migrations from continent to continent, suggested by Cuvier to explain the replacement of the animal life which had become extinct through sudden geologic changes, was prophetic of one of the chief features of modern method—namely, the tracing of migrations. ”

“ Origin from Primitive or Stem Forms.—As already observed, the same principles apply to groups of animals as to organs and groups of organs; an organ originates in a primitive and unspecialized stage, a group of animals originates in a primitive or stem form. It was early perceived by Huxley, Cope and many others that Cuvier’s broad belief in a universal progression was erroneous, and there developed the distinction between “persistent primitive types” (Huxley) and “progressive types.” ”

“ It was Alcide Dessalines d'Orbigny (1802-1857) who pushed to an extreme Cuvier's ideas of the fixity of species and of successive extinctions, and finally developed the wild hypothesis of twenty-seven distinct creations. While these views were current in France, exaggerating and surpassing the thought of Cuvier, they were strongly opposed in Germany by such authors as Ernst Friedrich von Schlotheim (1764-1832) and Heinrich Georg Bronn (1800-1862) ; and the latter demonstrated that certain species actually pass from one formation to another. ”

“ This independence of adaptation applies to every detail of structure; the six cusps of a grinding tooth may all evolve alike, or each may evolve independently and differently. Independent evolution of parts is well shown among invertebrates, where the shell of an ammonite, for example, may change markedly in form without a corresponding change in suture, or vice versa. ”

“ The ingenuity of nature, however, in adapting animals is not infinite, because the same devices are repeatedly employed by her to accomplish the same adaptive ends whether in fishes, reptiles, birds or mammals; thus she has repeated herself at least twenty-four times in the evolution of long-snouted rapacious swimming types of animals. ”