In the meantime, the great master, Darwin, had decided to deal with this chief evolutionary problem in a special work. The two volumes of his Descent of Man appeared in 1871. They contained an able discussion of sexual selection, or the selective influence of sexual love and high psychic activities connected therewith, and their significance in regard to the origin of man. As this part of Darwin's work was afterwards attacked with particular virulence, I will say that, in my opinion, it is of the greatest importance, not only for the general theory of evolution, but also for psychology, anthropology, and æsthetics.
My own feeble early efforts (1866), not only to establish the descent of man from the nearest related apes, but also to determine more precisely the long series of our earlier and lower vertebrate ancestors, had not at all satisfied me. In particular, I had had to leave unanswered in my General Morphology the very interesting question: from which invertebrate animals the vertebrate stem originally came. A clear and unexpected light was thrown on it some time afterwards by the astounding discoveries of Kowalevsky, which revealed an essential agreement in embryonic development between the lowest vertebrate (Amphioxus) and a lowly tunicate (Ascidia). In the succeeding years, the numerous discoveries in connection with the formation of the germinal layers in different animals so much enlarged our embryological outlook that I was able to prove the complete homology of the two-layered gastrula (a cup-shaped embryonic form) in all the tissue-forming animals (metazoa) in my Monograph on the Sponges. From this I inferred, in virtue of the biogenetic law, the common descent of all the metazoa from one and the same gastrula-shaped stem-form, the gastræa. This hypothetical stem-form, to which man's earliest multicellular ancestors also belong, was afterwards proved by Monticelli's observations to be still in existence. The evolution of these very simple tissue-forming animals from still simpler unicellular forms (protozoa) is shown by the corresponding processes that we witness in what is called the segmentation of the ovum or gastrulation, in the development of the two-layered germ from the single cell of the ovum.
Encouraged by these great advances of modern phylogeny, and with the support of many new discoveries in comparative anatomy and embryology, in which a number of distinguished observers were at work, I was able in 1874 to venture on the first attempt to trace continuously the whole story of man's evolution. In doing so, I took my stand on the firm ground of the biogenetic law, seeking to give a phylogenetic cause for each fact of embryology. My Evolution of Man, which made the first attempt to accomplish this difficult task, was materially improved and enlarged as new and important discoveries were made. The latest edition (1903 [1904 in English]) contains thirty chapters distributed in two volumes, the first of which deals with embryology (or ontogeny), and the second with the development of species (or phylogeny).
Though I was quite conscious that there were bound to be gaps and weak points in these first attempts to frame a natural anthropogeny, I had hoped they would have some influence on modern anthropology, and especially that the first sketches of a genealogical tree of the animal world would prove a stimulus to fresh research and improvement. In this I was much mistaken. The dominant school of anthropology, especially in Germany, declined to suffer the introduction of the theory of evolution, declaring it to be an unfounded hypothesis, and described our carefully prepared ancestral trees as mere figments. This was due, in the first place, to the great authority of the founder and president (for many years) of the German Anthropological Society, Rudolf Virchow, as I briefly pointed out in the previous chapter. In view of the great regard that is felt for this distinguished scientist, and the extent to which his powerful opposition prevented the spread of the theory, it is necessary to deal more fully with his position on the subject. I am still further constrained to do this because of the erroneous views of it that are circulating, and my own fifty years' acquaintance with my eminent teacher enables me to put them right.
Not one of Virchow's numerous pupils and friends can appreciate more than I do his real services to medical science. His Cellular Pathology (1858), his thorough application of the cell-theory to the science of disease, is, in my opinion, one of the greatest advances made by modern medicine. I had the good fortune to begin my medical studies at Würzburg in 1852, and to spend six valuable terms under the personal guidance of four biologists of the first rank—Albert Kölliker, Rudolf Virchow, Franz Leydig and Carl Gegenbaur. The great stimulus that I received from these distinguished masters in every branch of comparative and microscopic biology was the starting-point of my whole training in that science, and enabled me subsequently to follow with ease the higher intellectual flight of Johannes Müller. From Virchow especially I learned, not only the analytic art of careful observation and judicious appreciation of the detailed facts of anatomy, but also the synthetic conception of the whole human frame, the profound conviction of the unity of our nature, the inseparable connection of body and mind, to which Virchow gave a fine expression in his classic essay on "The Efforts to bring about Unity in Scientific Medicine" (1849). The leading articles which he wrote at that time for the Journal of Pathological Anatomy and Physiology, which he had founded, contain much new insight into the wonders of life, and a number of excellent general reflections on their significance—pregnant ideas that we can make direct use of for Monistic purposes. In the controversy that broke out between empirical rationalism and materialism and the older vitalism and mysticism, he took the side of the former, and fought together with Jacob Moleschott, Carl Vogt, and Ludwig Büchner. I owe the firm conviction of the unity of organic and inorganic nature, of the mechanical character of all vital and psychic activity, which I have always held to be the foundation of my Monistic system, in a great measure to Virchow's teaching and the exhaustive conversations I had with him when I was his assistant. The profound views of the nature of the cell and the independent individuality of these elementary organisms, which he advanced in his great work Cellular Pathology, remained guiding principles for me in the prolonged studies that I made thirty years afterwards of the organisation of the radiolaria and other unicellular protists; and also in regard to the theory of the cell-soul, which followed naturally from the psychological study of it.
His life at Würtzburg was the most brilliant period of Virchow's indefatigable scientific labours. A change took place when he removed to Berlin in 1856. He then occupied himself chiefly with political and social and civic interests. In the last respect he has done so much for Berlin and the welfare of the German people that I need not enlarge on it. Nor will I go into his self-sacrificing and often thankless political work as leader of the progressive party; there are differences of opinion as to its value. But we must carefully examine his peculiar attitude towards evolution, and especially its chief application, the ape-theory. He was at first favourable to it, then sceptical, and finally decidedly hostile.
When the Lamarckian theory was brought to light again by Darwin in 1859, many thought that it was Virchow's vocation to take the lead in defending it. He had made a thorough study of the problem of heredity; he had realised the power of adaptation through his study of pathological changes; and he had been directed to the great question of the origin of man by his anthropological studies. He was at that time regarded as a determined opponent of all dogmas; he combated transcendentalism either in the form of ecclesiastical creeds or anthropomorphism. After 1862 he declared that "the possibility of a transition from species to species was a necessity of science." When I opened the first public discussion of Darwinism at the Stettin scientific congress in 1863, Virchow and Alexander Braun were among the few scientists who would admit the subject to be important and deserving of the most careful study. When I sent to him in 1865 two lectures that I had delivered at Jena on the origin and genealogical tree of the human race, he willingly received them amongst his Collection of Popular Scientific Lectures. In the course of many long conversations I had with him on the matter, he agreed with me in the main, though with the prudent reserve and cool scepticism that characterised him. He adopts the same moderate attitude in the lecture that he delivered to the Artisans' Union at Berlin in 1869 on "Human and Ape Skulls."
His position definitely changed in regard to Darwinism from 1877 onward. At the Scientific Congress that was then held at Munich I had, at the pressing request of my Munich friends, undertaken the first address (on 18th September) on "Modern Evolution in Relation to the whole of Science." In this address I had substantially advanced the same general views that I afterwards enlarged in my Monism, Riddle of the Universe, and Wonders of Life. In the ultramontane capital of Bavaria, in sight of a great university which emphatically describes itself as Catholic, it was somewhat bold to make such a confession of faith. The deep impression that it had made was indicated by the lively manifestations of assent on the one hand, and displeasure on the other, that were at once made in the Congress itself and in the Press. On the following day I departed for Italy (according to an arrangement made long before). Virchow did not come to Munich until two days afterwards, when he delivered (on 22nd September, in response to entreaties from people of position and influence) his famous antagonistic speech on "The Freedom of Science in the Modern State." The gist of the speech was that this freedom ought to be restricted; that evolution is an unproved hypothesis, and ought not to be taught in the school because it is dangerous to the State: "We must not teach," he said, "that man descends from the ape or any other animal." In 1849, the young Monist, Virchow, had emphatically declared this conviction, "that he would never be induced to deny the thesis of the unity of human nature and its consequences"; now, twenty-eight years afterwards, the prudent Dualistic politician entirely denied it. He had formerly taught that all the bodily and mental processes in the human organism depend on the mechanism of the cell-life; now he declared the soul to be a special immaterial entity. But the crowning feature of this reactionary speech was his compromise with the Church, which he had fought so vigorously twenty years before.
The character of Virchow's speech at Munich is best seen in the delight with which it was at once received by the reactionary and clerical papers, and the profound concern of all Liberal journals, either in the political or the religious sense. When Darwin read the English translation of the speech he—generally so gentle in his judgments—wrote: "Virchow's conduct is shameful, and I hope he will some day feel the shame." In 1878, I made a full reply to it in my Free Science and Free Teaching, in which I collected the most important press opinions on the matter.[6]
From this very decided turn at Munich until his death, twenty-five years afterwards, Virchow was an indefatigable and very influential opponent of evolution. In his annual appearances at congresses he has always contested it, and has obstinately clung to his statement that "it is quite certain that man does not descend from the ape or any other animal." To the question: "Whence does he come, then?" he had no answer, and retired to the resigned position of the Agnostic, which was common before Darwin's time: "We do not know how life arose, and how the various species came into the world." His son-in-law, Professor Rabl, has tried to draw attention once more to his earlier conception, and has declared that even in later years Virchow often recognised the truth of evolution in private conversation. This only makes it the more regrettable that he always said the contrary in public. The fact remains that ever since the opponents of evolution, especially the reactionaries and clericals, have appealed to the authority of Virchow.