CHAPTER XVIII THE EVOLUTION OF EVOLUTION THEORIES 1. Greek Philosophers—2. Aristotle-3. Lucretius-4. Evolutionists before Darwin-5. Three old Masters: Buffon, Erasmus Darwin, Lamarck-6. Charles Darwin-7. Darwin's Fellowworkers-8. The Present State of Opinion THE Conception of evolution is no new idea, it is the human idea of history grown larger, large enough to cover the whole world. The extension of the idea was gradual, as men felt the need of extending it; and at the same moment we find men believing in the external permanence of one set of phenomena, in the creation of others, in the evolution of others. One authority says human institutions have been evolved; man was created; the heavens are eternal. According to another, matter and motion are eternal; life was created; the rest has been evolved, except, perhaps, the evolution theory which was created by Darwin. 1. Greek Philosophers. Of the wise men of Greece and what they thought of the nature and origin of things, I shall say little, for I have no direct acquaintance with the writings of those who lived before Aristotle. Moreover, though an authority so competent as Zeller has written on the "Grecian predecessors of Darwin," most of them were philosophers not naturalists, and we are apt to read our own ideas into their words. They thought, indeed, as we are thinking, about the physical and organic universe, and some of them believed it to be, as we do, the result of a process; but here in most cases ends the resemblance between their thought and ours. Thus when Anaximander spoke of a fish-like stage in the past history of man, this was no prophecy of the modern idea that a fish-like form was one of the far-off ancestors of backboned animals, it was only a fancy invented to get over a difficulty connected with the infancy of the first human being. Or, when we read that several of these sages reduced the world to one element, the ether, we do the progress of knowledge injustice if we say that men are simply returning to this after more than two thousand years. For that conception of the ether which is characteristic of modern physical science has been, or is being, slowly attained by precise and patient analysis, whereas the ancient conception was reached by metaphysical speculation. If we are returning to the Greeks, it is on a higher turn of the spiral, so far at least as the ether is concerned. When we read that Empedocles sought to explain the world as the result of two principles—love and hate— working on the four elements, we may, if we are so inclined, call these principles "attractive and repulsive forces"; we may recognise in them the altruistic and individualistic factors in organic evolution, and what not; but Empedocles was a poetic philosopher, no far-sighted prophet of evolution. But the student cannot afford to overlook the lesson which Democritus first clearly taught, that we do not explain any result until we find out the natural conditions which bring it about, that we only understand an effect when we are able to analyse its causes. We require a socalled "mechanical," or more strictly, a dynamical explanation of results. It is easy to show that it is advantageous for a root to have a root-cap, but we wish to know how the cap comes to be there. It is obvious that the antlers of a stag are useful weapons, but we must inquire as precisely as possible how they first appeared and still grow. 2. Aristotle. As in other departments of knowledge, so in zoology the work of Aristotle is fundamental. It is wonderful to think of his knowledge of the forms and ways of life, or the insight with which he foresaw such useful distinctions as that between analogous and homologous organs, or his recognition of the fact of correlation, of the advantages of division of labour within organisms, of the gradual differentiation observed in development. He planted seeds which grew after long sleep into comparative anatomy and classification. Yet with what sublime humility he says: "I found no basis prepared, no models to copy. Mine is the first step, and therefore a small one, though worked out with much thought and hard labour." Aristotle was not an evolutionist, for, although he recognised the changefulness of life, the world was to him an eternal fact not a stage in a process. "In nature, the passage from inanimate things to animals is so gradual that it is impossible to draw a hard-and-fast line between them. After inanimate things come plants, which differ from one another in the degree of life which they possess. Compared with inert bodies, plants seem endowed with life; compared with animals, they seem inanimate. From plants to animals the passage is by no means sudden or abrupt; one finds living things in the sea about which there is doubt whether they be animals or plants." "Animals are at war with one another when they live in the same place and use the same food. If the food be not sufficiently abundant they fight for it even with those of the same kind." 3. Lucretius. Among the Romans Lucretius gave noble expression to the philosophy of Epicurus. I shall not try to explain his materialistic theory of the concourse of atoms into stable and well-adapted forms, but rather quote a few sentences in which he states his belief that the earth is the mother of all life, and that animals work out their destiny in a struggle for existence. He was a cosmic, but hardly an organic evolutionist, for, according to his poetic fancy, organisms arose from the earth's fertile bosom and not by the gradual transformation of simpler predecessors. "In the beginning the earth gave forth all kinds of herbage and verdant sheen about the hills and over all the plains; the flowery meadows glittered with the bright green hue, and next in order to the different trees was given a strong and emulous desire of grow With good ing up into the air with full unbridled powers. reason the earth has gotten the name of mother, since all things have been produced out of the earth. "We see that many conditions must meet together in things in order that they may beget and continue their kinds; first a supply of food, then a way in which the birth-producing seeds throughout the frame may stream from the relaxed limbs. . . . And many races of living things must then have died out and been unable to beget and continue their breed. For in the case of all things which you see breathing the breath of life, either craft or courage or else speed has from the beginning of its existence protected and preserved each particular race. And there are many things which, recommended to us by their useful services, continue to exist consigned to our protection. "In the first place, the first breed of lions and the savage races their courage has protected, foxes their craft, and stags their proneness to flight. But light-sleeping dogs with faithful heart in breast, and every kind which is born of the seed of beasts of burden, and at the same time the woolly flocks and the horned herds, are all consigned to the protection of man. For they have ever fled with eagerness from wild beasts, and have ensued peace, and plenty of food obtained without their own labour, as we give it in requital of their useful services. But those to whom nature has granted none of these qualities, so that they could neither live by their own means nor perform for us any useful service, in return for which we should suffer their kind to feed and be safe under our protection, those, you are to know, would lie exposed as a prey and booty of others, hampered all in their own death-bringing shackles, until nature brought that kind to utter destruction." 4. Evolutionists before Darwin.-From Lucretius I shall pass to Buffon, for the intervening centuries were uneventful as regards zoology. Hugo Spitzer, one of the historians of evolution, finds analogies between certain mediæval scholastics and the Darwinians of the nineteenth century, but these are subtle comparisons. Yet long before Darwin's day there were evolutionists, and the first of these who can be called great was Buffon. We must guard against supposing that the works of Buffon, or Lamarck, or Darwin were inexplicable creations of genius, or that they came like cataclysms, without warning, to shatter the conventional traditions of their time. For all great workers have their forerunners, who prepare their paths. Therefore in thinking out the history of evolutionist theories before that of Buffon, we must take account of many forces which began to be influential from the twelfth century onwards. "Evolution in social affairs has not only suggested our ideas of evolution in the other sciences, but has deeply coloured them in accordance with the particular phase of social evolution current at the time.” 1 In other words, we must abandon the idea that we can understand the history of any science as such, without reference to contemporary evolution in other departments of activity. The evolution of theories of evolution is bound up with the whole progress of the world. In trying to determine those social and intellectual forces of which the modern conception of organic evolution has been a resultant, we should take account of social changes, such as the collapse of the feudal system, the crusades, the invention of printing, the discovery of America, the French Revolution, the beginning of the steam age; of theological and religious movements, such as the Protestant Reformation and the spread of Deism; of a long series of evolutionist philosophers, some of whom were at the same time students of the physical sciences, notably Descartes, Spinoza, Leibnitz, Herder, Kant, and Schelling; of the acceptance of evolutionary conceptions in regard to other orders of facts, especially in regard to the earth and the solar system; and, finally, of those few naturalists, like De Maillet and Robinet, who, before Buffon's day, whispered evolutionist heresies. The history of an idea is like that of an organism in which cross-fertilisation and composite inheritance complicate the pedigree. 5. Three old Masters.-Among the evolutionists before Darwin I shall speak of only three—Buffon, Erasmus Darwin, and Lamarck. BUFFON (1707-1788) was born to wealth and was wedded to Fortune. He sat in kings' houses, his statue adorned their gardens. As Director of the Jardin du Roi he had opportunity to acquire a wide knowledge of animals. He commanded the assistance of able collaborateurs, and his own 1 Article "Evolution" (P. Geddes) in Chambers's Encyclopædia. |