When the first edition of the "Origin of Species" was published in 1859, Darwin wrote that he by no means expected to convince experienced naturalists whose minds were stocked with a multitude of facts, all regarded during a long course of years from a point of view directly opposite to his. He looked forward with confidence, however, to the future, to young and rising naturalists, who would be able to view both sides of the question with impartiality. He predicted that, when the conclusions reached by him and by Mr. Wallace concerning the origin of species should be generally accepted, there would be a considerable revolution in natural history. Naturalists, for instance, would be forced to acknowledge that the only distinction between species and well-marked varieties is that the latter are known or believed to be connected at the present day by intermediate gradations, whereas species were formerly, though they are not now, thus connected. It might thus come to pass that forms generally acknowledged in 1859 to be merely varieties, would thereafter be thought worthy of specific names; in which case scientific and common language would come into accordance. In short, Darwin looked forward to the time when species would have to be treated in the same manner as genera are treated by those naturalists who admit that genera are merely artificial combinations made for convenience.
Darwin also foresaw that when his theory of the origin of species should be adopted, other and more general departments of natural history would rise greatly in interest. The terms used by naturalists--such terms as affinity, relationship, community of type, paternity, morphology, adaptive characters, rudimentary and abortive organs, etc.--would cease to be metaphorical, and would have a plain signification. "When," he wrote, "we no longer look at an organic being as a savage looks at a ship, as something wholly beyond his comprehension; when we regard every production of nature as one which has had a long history; when we contemplate every complex structure and instinct as the summing up of many contrivances, each useful to the possessor, in the same way as any great mechanical invention is the summing up of the labor, the experience, the reason, and even the blunders of numerous workmen; when we thus view each organic being, how far more interesting--I speak from experience--does the study of natural history become." Once more: "When we can feel assured that all the individuals of the same species, and all the closely allied species of most genera, have within a not very remote period descended from one parent, and have migrated from some one birthplace; and when we better know the many means of migration, then, by the light which geology now throws, and will continue to throw, on former changes of climate and of the level of the land, we shall surely be enabled to trace in an admirable manner the former migrations of the inhabitants of the whole world."
When Darwin published the "Origin of Species," he was aware that theologians and philosophers seemed to be fully satisfied with the view that each species had been independently created, and was immutable. To his own mind, however, it accorded better with what was known of the laws impressed on matter by the Creator that the production and extinction of the past and present inhabitants of the world should have been due to secondary causes like those determining the birth and death of the individual. "When I view," he said, "all beings not as special creations, but as the lineal descendants of some few beings which lived long before the first bed of the Cambrian system was deposited, they seem to me to become ennobled." And again: "As all the living forms of life are the lineal descendants of those which lived long before the Cambrian epoch, we may feel certain that the ordinary succession by generation has never once been broken, and that no cataclysm has desolated the whole world. Hence we may look with some confidence to a secure future of great length. And as natural selection works slowly by and for the good of each being, all corporeal and mental endowments will tend to progress towards perfection."
For his own part, Darwin could see no good reason why the views propounded in the two volumes comprising the "Origin of Species" should shock the religious feelings of any one. Touching the likelihood of such a result, he reassured himself by recalling the fact that the greatest discovery ever made by man--namely, the law of the attraction of gravitation--was attacked by Leibnitz "as subversive of natural, and inferentially, of revealed, religion." Darwin was confident that, if any such impressions were made by his theory, they would prove but transient, and that ultimately men would come to see that it is just as noble a conception of the Deity to believe that He created a few original forms capable of self-development into other and needful forms as to believe that it required the fresh act of creation to supply the voids caused by the action of His laws.
IV.
It was, as we have said, in 1868 that Darwin published the two volumes collectively entitled "Variation of Animals and Plants under Domestication." It is the second and largely corrected edition brought out in 1875 which we have under our eye. It is the outcome of the views maintained by the author in this work and elsewhere that not only the various domestic races but the most distinct genera and orders within the same great class--for instance, mammals, birds, reptiles, and fishes--are all the descendants of one common progenitor, and the whole vast amount of difference between these forms has primarily arisen from simple variability. Darwin recognized that he who for the first time should consider the subject under this point of view would be struck dumb with amazement. He submits, however, that the amazement ought to be lessened when we reflect that beings almost infinite in number during an almost infinite lapse of time have often had their whole organization rendered in some degree plastic, and that each slight modification of structure which was in any way beneficial under excessively complex conditions of life has been preserved, whilst each which was in any way injurious has been rigorously destroyed. The long-continued accumulation of beneficial variations will infallibly have led to structures as diversified, as beautifully adapted for various purposes, and as excellently co-ordinated as we see in the animals and plants around us. Hence Darwin regards selection as the paramount power, whether applied by man to the formation of domestic beings or by nature to the production of species. Employing a favorite metaphor, he said: "If an architect were to rear a noble and commodious edifice without the use of cut stone, by selecting from the fragments at the base of a precipice wedge-form stones for his arches, elongated stones for his lintels, and flat stones for his roof, we should admire his skill and regard him as the paramount power. Now, the fragments of stone, though indispensable to the architect, bear to the edifice built by him the same relation which the fluctuating variations of organic beings bear to the varied and admirable structures ultimately acquired by their modified descendants."
Some critics of the Darwinian theory of the origin of species have declared that natural selection explains nothing, unless the precise cause of each slight individual difference be made clear. Darwin rejoins that if it were explained to a savage utterly ignorant of the art of building how the edifice had been raised, stone upon stone, and why wedge-formed fragments were used for the arches, flat stones for the roof, etc.; and if the use of each part and of the whole building were pointed out,--it would be unreasonable if he declared that nothing had been made clear to him, because the precise cause of the shape of each fragment could not be told. This, in Darwin's opinion, is a nearly parallel case, with the objection that selection explains nothing because we know not the cause of each individual difference in the structure of each being. The shape of the fragments of stone at the base of the hypothetical precipice may be called accidental, but the term is not strictly applicable; for the shape of each depends on a long sequence of events, all obeying natural laws; on the nature of the rock, on the lines of deposition or cleavage, on the form of the mountain, which depends on its upheaval and subsequent denudation, and, lastly, on the storm or earthquake which throws down the fragments.
In regard to the use, however, to which the fragments may be put, their shape may be strictly said to be accidental. Here Darwin acknowledged that we are brought face to face with a great difficulty in alluding to which he felt that he was travelling beyond his proper province. "An omniscient Creator must have foreseen every consequence which results from the laws imposed by Him. But can it be reasonably maintained that the Creator intentionally ordered, if we use the words in any ordinary sense, that certain fragments of rock should assume certain shapes, so that the builder might erect his edifice? If the various laws which have determined the shape of each fragment were not predetermined for the builder's sake, can it be maintained with any greater probability that He specially ordained for the sake of the breeder each of the innumerable variations in our domestic animals and plants,--many of these variations being of no service to man, and not beneficial, far more often injurious, to the creatures themselves? Did He ordain that the crop and tail-feathers of the pigeon should vary in order that the fancier might make his grotesque pouter and fan-tail breeds? Did He cause the frame and mental qualities of the dog to vary in order that a breed might be formed of indomitable ferocity with jaws fitted to pin down the bull for man's brutal sport?"
It is obvious, however, that if we give up the principle in one case,--if we do not admit that the variations of the primeval dog were intentionally guided in order that the greyhound, for instance, that perfect image of symmetry and vigor, might be formed,--no shadow of reason can be assigned for the belief that variations similar in nature and the result of the same general laws which have been the groundwork through natural selection of the formation of the most perfectly adapted animals in the world, man included, were intentionally and specially guided. Darwin, therefore, was unable to follow the distinguished botanist, Prof. Asa Gray, in his belief that "variation has been led along certain beneficial lines," like a stream "along definite and useful lines of irrigation." Darwin's conclusion was that, if we assume that each particular variation was from the beginning of all time preordained, then that plasticity of organization which leads to many injurious deviations of structure, as well as the redundant power of reproduction which inevitably leads to a struggle for existence, and, as a consequence, to a natural selection or survival of the fittest, must appear to us superfluous laws of nature.