Popular Science Monthly/Volume 74/April 1909/Predarwinian and Postdarwinian Biology
| PREDARWINIAN AND POSTDARWINIAN BIOLOGY[1] |
By Professor WILLIAM MORTON WHEELER
HARVARD UNIVERSITY
CHARLES DARWIN undoubtedly exerted a profound and threefold influence on botany, zoology and all the kindred sciences; first, by his rehabilitation of Lamarck's theory of transformism, or evolution, as it is more generally but less aptly called; secondly, by his wonderful studies on variation; and thirdly, by the announcement of his brilliant theory of natural selection through the survival of the fittest. There is much difference of opinion as to which of these constitutes Darwin's most glorious achievement. Neodarwinists regard the promulgation of the theory of natural selection as his greatest work; experimental zoologists and botanists attribute to his studies on variation a deeper and more salutary influence on present and future investigation; while Neolamarckians insist that his labors in the cause of evolution in general, quite irrespective of whether it be conceived to result from natural selection or from other factors, is his most important contribution, not only to biological science, but to the whole body of modern thought. With this last estimate I believe that most conservative men of science will agree. Just how Darwin's work has compelled us to change our attitude so radically towards the world about us can be made clear if you will permit me very briefly to contrast the tendencies of ancient and modern science.
The unceasing flux of phenomena which is all that science can deal with has been envisaged very differently by ancient and modern observers. The Greek scientist fixed his attention on particular moments or aspects of phenomena, so that science became to him a static edifice of concepts or ideas, a hierarchy of genera and species. The scientist of to-day does not thus concentrate his attention on single moments to the exclusion or neglect of all other aspects of a phenomenon, but seeks to obtain a complete knowledge of the uniformities and constants in its occurrence and recurrence. For this reason modern science is dynamic and lays stress on laws and not on the definition and classification of concepts and ideas. These important differences between ancient and modern science have been clearly pointed out by the eminent French philosopher, Henri Bergson, in the following words:
To Aristotle we may also turn for a biological illustration of the differences between ancient and modern scientific observation. According to his conception, the type or privileged moment of humanity is represented by the adult male individual, with reference to whom youth and age are merely incipient and declining stages respectively, and woman is merely an abortive attempt on the part of nature to produce a man. Contrast with this our present biological conception of the sexes and the ontogeny of the human species!
It must be admitted that the tendency of modern science is in the direction of much greater refinement on the ancient method, a tendency to scrutinize more humbly and more closely, and hence, to multiply indefinitely the observed moments and aspects. I, therefore, do not use the term "ancient" in the sense of "no longer existing," since the tendency thus designated is still constantly manifested in all our ordinary thinking. To observe and retain only the privileged moments and aspects of things is for very many purposes eminently practical, but it has its disadvantages, for the more such moments of an object are accentuated or exalted, the more insignificant or debased become its other aspects. Such emphasis may be highly artistic, but it is contrary to the spirit of modern science. Indeed, much of the lack of sympathy that exists between men of extremely artistic and extremely scientific temperament is due to this difference of instinctive attitude towards the world of phenomena.
It is well known that in their development the biological have always lagged behind the physical sciences. This is attributable in large measure, of course, to the greater complexity of organic phenomena, but I suspect that the fact that animals and plants admit of an arrangement in generic and specific categories, which seem at first sight to be in singular harmony with the spirit of ancient science and philosophy, may be to a considerable extent responsible for the stolid conservatism of systematic biology. At a time when the physical sciences, through the labors of Kepler, Gallilei and Newton, had already become modern sciences in the true sense of the word, biology was still practically in the Greek stage. This is certainly true of zoology and botany proper up to the middle of the last century, although zoology had through medicine contracted some of the modern spirit, since by that time anatomy and physiology had definitively abandoned Greek and scholastic methods.
At this juncture appeared Darwin's "Origin of Species." The effect of this work was in the first instance destructive, for it tended to dissolve and mobilize the rigid conceptual schematism that dominated, not only the zoology and botany, but the whole cosmology of the time. The conception of an evolution which melted all living beings, man included, into a single vital stream, surging on into the future as it has surged through the æons of the past, continually creating new and destroying old forms, could not fail to clash with the conception of a world created once for all and since engaged very largely in marking time. According to the old view, living objects are more or less vitiated Platonic ideas or Aristotelian forms, according to the new they are eddies or whirlpools in a living current that modify and regulate their movements according to the obstacles, i. e., the "environment" which they encounter. No wonder men like Cuvier declined to accept the doctrine of evolution when it was first promulgated by Lamarck, and that von Baer and Louis Agassiz regarded its rehabilitation by Darwin as a heresy. All of these men believed in the existence of permanent types of organic structure, which, after all, were merely Platonic ideas parading under assumptions more or less theological, privileged moments or aspects of animal and plant morphology interpreted as thoughts of the Deity. It is quite unnecessary to mention the innumerable scholastic and theological opponents of evolution. Their animosity certainly had and still has other motives than a predilection for the Mosaic account of creation.
It is far pleasanter to contemplate the constructive aspects of Darwin's work. Since evolution, as conceived by him, admitted of a mechanical explanation—for survival through natural selection is mechanical and not teleological like survival through psychical effort as postulated by Lamarck—it breathed the spirit of the physical sciences and therefore allied itself with these rather than with psychology and philosophy. When presented with Darwin's conception of evolution, the botanist and zoologist could no longer remain satisfied with mere contemplation of privileged moments. It became necessary to attend to every aspect of the organism. Every phase of its development from the egg to its dissolution, and every particle of its structure had to be submitted to the closest examination, for no character—so ran the theory—was too insignificant to decide whether a species could survive in the struggle for existence. Indeed, even vestigial and rudimental characters began to assume an astonishing importance as witnessing to the past and prefiguring the future history of the species. Such close scrutiny of the entire life-cycle and structure of organisms was also necessitated by Darwin's assumption that the evolution of organic forms is a very gradual process, requiring enormous periods of time. Hence the incentive to record the minutest variations and adaptations and to search for their causes. From the same source sprang the inspiration to study the lower animals and plants with the utmost care and in all their aspects, for these forms—according to the theory—had departed least from the first, simple beginnings of life on our planet, and might, therefore, be expected to throw light on the initial movements of organic evolution. But the animals at the other end of the organic scale were not to be neglected, for the theory which made man a blood relation of the higher mammals could not fail to arouse universal interest in these and all the other vertebrates. And not only did it become necessary to investigate the plants and animals now living on the earth, but the strata of the planet had to be ransacked for evidences of past evolutionary history. Paleontology was born anew, and the distribution of life in the present and past became a subject of absorbing and ardent study. Even the most conservative branch of biology, the classification of animals and plants, was shaken to its foundations by the theory of evolution, for under its solvent action the old conceptions of the genus and species, and all the other taxonomic categories, lost their rigid outlines and became fluid and dynamic. In proof of all these statements concerning the immediate effects of the promulgation of the theory of evolution, we have only to glance at the marvelous development during the past fifty years of anatomy, embryology, histology, cytology and physiology, both human and comparative, and of paleontology, chorology, ethology and taxonomy, both botanical and zoological. The constantly increasing tendency during the past half century to substitute a careful genetic study, that is, a study of all the stages of the life-processes, with a view to establishing the laws or constants of their occurrence, for the ancient cut and dried methods of defining and classifying concepts obtained from the contemplation of privileged moments in the vital flux, has spread far beyond the confines of biology properly so-called. Psychology, which is the most closely related of all the mental sciences to biology, has been revolutionized. Its students have abandoned the old facultative and associationist schematism and turn with renewed interest to the psychology of emotion, volition and instinct, to animal and child psychology and the normal and pathological psychology of the various human races. Mind is no longer looked upon as a thing, but as a living process, the study of which must be undertaken with far subtler methods than were ever dreamed of by the ancient and mediæval psychologists. Philosophy, ethics and religion, which are all so intimately bound up with psychology, are also at last breaking away from conceptualism and absolutism. This is clearly seen in the works of the pragmatists and humanists, and among theological writings in what has been called modernism. These tendencies of the mental sciences have also reached out into sociology, anthropology, archeology, philology, economics and education. Even the fine arts, though still necessarily addicted to the glorification of certain privileged or dramatic moments, have been seized with the modern scientific craving to multiply these moments indefinitely and thus to increase our delight and interest in the full efflorescence of life and its cosmic setting.
Some may doubt whether these marvelous changes in all modern intellectual endeavor have been brought about by the doctrine of evolution. Of course, even if Darwin had never lived and if the doctrine of evolution had never been revived, it is certain that the biological sciences would have developed considerably during the past fifty years merely by following in the footsteps and by adopting the methods of physics and chemistry, but that Darwin's thought quickened, exaggerated and dominated this development cannot be doubted. And even if we go so far as to say that natural selection may eventually prove to be an unimportant factor in evolution, to be consigned to the limbo of defunct hypotheses, together with Darwin's views on pangenesis, sexual selection and the origin of species from fluctuating variations, we must, I believe, still admit that the great English naturalist opened up before us a vast new world of thought and endeavor. But for the doctrine of evolution we should still be contemplating living organisms from afar and in a more or less scholastic and theologizing spirit, like the biologists of the first half of the nineteenth century, and not as now, at close range and with a deeper and freer insight into the significance of the minutest details of development, structure and function.