The Evolution Theory, Vol. 1 of 2

by August Weismann

It is impossible to estimate the effect of Darwin's book on The Origin of Species, published in English in 1858, in German in 1859 unless we fully realize how completely the biologists of that time had turned away from general problems. I can only say that we, who were then the younger men, studying in the fifties, had no idea that a theory of evolution had ever been put forward, for no one spoke of it to us, and it was never mentioned in a lecture. It seemed as if all the teachers in our universities had drunk of the waters of Lethe, and had utterly forgotten that such a theory had ever been discussed, or as if they were ashamed of these philosophical flights on the part of natural science, and wished to guard their students from similar deviations. The over-speculation of the 'Naturphilosophie' had left in their minds a deep antipathy to all far-reaching deductions, and, in their legitimate striving after purely inductive investigation, they forgot that the mere gathering of facts is not enough, that the drawing of conclusions is an essential part of the induction, and that a mass of bare facts, however enormous, does not constitute a science.

One of my most stimulating teachers at that time, the gifted anatomist, Jacob Henle, had written as a motto under his picture, 'There is a virtue of renunciation, not in the province of morality alone, but in that of intellect as well,' a sentence which expressly indicated the desirability of refraining from all attempts to probe into the more general problems of life. Thus the young students of that time were nourished only on the results of detailed research, in part indeed interesting enough, but in part dry and, because uncorrelated, unintelligible in the higher sense, and only here and there awakening a deeper interest, when, as in physiology and in embryology, they formed a connected system in themselves. Without being fully clear as to what was lacking, we certainly missed the deeper correlation of the many separate disciplines.

It is therefore not to be wondered that Darwin's book fell like a bolt from the blue; it was eagerly devoured, and while it excited in the minds of the younger students delight and enthusiasm, it aroused among the older naturalists anything from cool aversion to violent opposition. The world was as though thunderstruck, as we can readily see from the preface with which the excellent zoologist of Heidelberg, Bronn, introduced his translation of Darwin's book, where he asks this question among others, 'How will it be with you, dear reader, after you have read this book?' and so forth.

But before I enter on a detailed examination of the contents of this epoch-making book, I should like to say a few words about the man himself, who thus revolutionized our thinking.

Charles Darwin was born in 1809, the year of the publication of Lamarck's Philosophie zoologique, and of Oken's Lehrbuch der Naturphilosophie. There was thus a whole generation between the first emergence of the Evolution theory and its later revival. Darwin's father was a physician, and his education was not a regular one. In his youth he seems to have devoted much time and enthusiasm to hunting, and only very slowly to have taken up regular studies towards a definite end. In accordance with his father's wishes, he studied medicine for a time, but soon abandoned it to devote himself to botany and zoology. Before he had had time to distinguish himself in any special way in these subjects, he was offered, in his twenty-first year, the post of naturalist on an English war-ship which was to make a voyage round the world, and that at a leisurely rate.

This was decisive not only for Darwin's immediate studies, but for the work of his life, for, as he tells us himself, it was during this voyage on the Beagle that the idea of the Evolution theory first came to him. While the vessel made a stay at the Galapagos Islands, west of South America, he noticed that quite a number of little land-birds occurred there which closely resembled those of the neighbouring mainland, but yet were different from them. Almost every little island had its own species, and so he concluded that all these might be descended from representatives of a few species which had long before drifted over from the mainland to these volcanic islands, become established there, and in the course of time taken on the character of new species. The problem of the transformation of species opened up before him, and he made up his mind to follow up the idea after his return, in the hope that by a patient collecting of facts, he would by and by arrive at some security with regard to this great question.

I need not linger over any detailed account of his travels; one can readily understand how a voyage round the world, lasting for five years, would offer to the inquiring mind of a Darwin rich opportunities for the most varied observations. That he did not fail to make use of these is evidenced not only by his book on The Origin of Species, but by several more special works, published shortly after his return—his natural history of those remarkable sessile crustaceans, the barnacles or Cirripedia, and his studies on the origin of coral reefs. The first-named book still holds its own as a classic monograph on this animal group, with its wealth of forms; and the theory of the origin of coral reefs which Darwin elaborated has still many adherents, in spite of various rival interpretations.

But Darwin would hardly have achieved what he did if he had been compelled to secure for himself a professional position in order to obtain bread and butter. Such great problems demand not only the whole of a man's mental energy, they monopolize his time. Studies of detail may well be taken up in leisure hours, but big problems absorb all the thoughts and must always be present to the mind, lest the connexion between the many individual inquiries, which make up the whole task, be lost sight of. Darwin had the good fortune to be a free investigator, and to be able to retire, on his return from his travels, to a small property at Down in Kent, there to live for his family and his work. Here he followed up the idea of evolution which he had already formulated, and it has always seemed to me the most remarkable thing about him, that he was able to keep in mind and work up the hundreds of isolated inquiries that were eventually to be brought together to form the main fabric of his theory. When one studies his many later writings, one cannot but be surprised afresh by the number of different sets of facts he collected at the same time, partly from others, partly from personal observation, and continually also from his own experiments. He made experiments on plants and on animals, and the number of people with whom he carried on a scientific correspondence is simply astounding. In this way he brought together, in the course of twenty years, an extraordinarily rich material of facts, from the fullness of which he was able later to write his book on The Origin of Species. Never before had a theory of evolution been so thoroughly prepared for, and it is undoubtedly to this that it owed a great part of its success; not to this alone, however, but still more, if not mainly, to the fact that it presented a principle of interpretation that had never before been thought of, but whose importance was apparent as soon as attention was called to it—the principle of selection.