1. There are not, as was at one time commonly supposed, broad and distinct lines of demarcation between the different varieties of animals and plants. Our increasing knowledge of zoology has brought to light the fact that one species shades off into another by almost imperceptible gradations. As we go back in the fossil records of animal life in the past, we find that the species now existing, while they are closely allied to correspondent species of an earlier period, are scarcely ever identical with them, and that the few cases of identity which do occur, are limited to the most recent rocks. Either then the old species must have perished, and new ones, similar but not identical, must have been created to take their places, or there must have been a process of gradual change, by which the present species have been derived from their predecessors. In one or two cases fossils have been found which combine, to some extent, forms which are now found in distinct species, as if the process of variation had proceeded in distinct lines from a common source.
2. No two animals of any class are exactly alike in all points. Each has its individual peculiarities, and in some cases these peculiarities are strongly marked.
3. Man has been enabled, to a certain extent, to make use of these individual peculiarities, and by means of them to produce great varieties in the breeds of domesticated animals. This has been sometimes done unconsciously through a selection influenced by other motives, and then the process has been very slow; but latterly intentionally, with a view to the production of improved breeds, and whenever this has been the case, changes of considerable extent have been rapidly produced. By carefully selecting the animals to be paired, any desired modification can generally be produced in the course of a few generations. This is exemplified in the numerous and increasing varieties of the breeds of almost all domestic animals and birds.
The theory of Evolution then suggests that the same processes which are employed by the cattle-breeder have been in operation through untold ages. For the intention and care of the human agent, Mr. Darwin substitutes two principles; one designated as "Natural Selection," the other as "Sexual Selection." For their full development he claims unlimited time. The ground on which the Process of Natural Selection is maintained is as follows:—
It has been already noticed that no two individuals of the same kind are exactly alike in all respects; each individual has some peculiarities, generally very trifling, but sufficient to distinguish it from all other individuals. Some of these peculiarities will probably be such as to be of some service to the individual in the struggle of life; they will assist it in procuring food, or in resisting or escaping from its natural enemies, while on the other hand the peculiarities of other individuals will be prejudicial to them in these ways. The consequence will be that a larger proportion of those having favourable peculiarities will survive and propagate their kind; their offspring will inherit the peculiarities of their parents, and reproduce them in various degrees. The same process will then be repeated, and thus from generation to generation the peculiarity will be increased, till at last it is sufficient to mark out, first a new variety, then a new species, and so on. This process then, continued through a long course of ages, was at one time considered by Mr. Darwin sufficient to account for all the varieties of living creatures now existing, or that have existed in past ages. But he has more recently satisfied himself [Footnote: Descent of Man, vol. i p. 152.] that there are many phenomena which are not satisfactorily accounted for by this principle, since many of the specific differences of animals are found to exist in matters which, cannot directly promote their success in the struggle of life. Such, for instance, are the brilliant colours which are found, especially among the males, in many species of birds. These he proposes to explain by the supplementary theory of "Sexual Selection." His suggestion is that these peculiarities are in some way attractive to animals of the opposite sex, so that the individuals in which they are most strongly developed are more successful than others in obtaining mates, and that in this way the peculiarity is gradually fixed and increased.
By these two processes, then, Mr. Darwin supposes that all the differences now existing among animals have been produced and perpetuated; and not only that, but that man also is the result of similar processes, acting through a very long period; that the progeny of certain "anthropomorphous apes" have, by slow degrees, risen in the scale of being above their progenitors; that all our faculties, intellectual and moral as well as physical, differ from those possessed by lower animals in DEGREE only, and not in KIND, [Footnote: Descent of Man, chaps, ii.-v.] so that man has arrived at his present state by what may be termed purely natural processes, without the intervention of any external power.
In considering these theories, our attention must first be directed to some defects which appear to weaken the whole course of the argument; and then we may consider the peculiar difficulties in the way of the processes of natural and sexual selection; and the grounds for the belief that man is in possession of something entirely different in KIND from any faculty or power possessed by any lower animals, which could not therefore be derived by inheritance and improvement.
The first thing which strikes us in Mr. Darwin's works is that, from time to time, he betrays a sort of latent consciousness that his theory is insufficient; that the processes to which he ascribes such vast results are not quite adequate to the purpose, but that they need in some way to be supplemented. Every now and then recourse is had to some law—some unknown cause—which must co-operate in the production of the results he is considering. In spite of the apparent care which he has taken to guard against it, he is continually betrayed into a confusion between the two senses in which the word "law" is employed. In its proper significance, law is an expression of the will of an intelligent superior, enforced by adequate power. In this sense the law may be considered as an efficient cause. The combination of will and power is an adequate cause for any result whatever. But Mr. Darwin expressly excludes this sense of the word, in a sentence which seems to involve a self-contradiction. "I mean by nature only the aggregate action and product of many natural laws, and by law only the ascertained sequence of events." [Footnote: Plants and Animals under Domestication, vol. i. p. 6.] Law, in this sense, then, is simply the statement of observed facts, and as such can have no action at all. It asserts that certain phenomena do uniformly follow each other in an ascertained order; but it gives us no information whatever as to the cause of those events, or the reason why they do thus succeed each other. But, taking law in this last sense, by his own definition, Mr. Darwin does, nevertheless, continually bring forward certain "laws" as accounting for certain results. Thus, we have the laws of "Correlation of Growth," [Footnote: Origin of Species, ed. 1872, p. 114.] "Inheritance limited to Males," [Footnote: Descent of Man, vol. i. pp. 256, 257.] and a "Principle of Compensation." [Footnote: Origin of Species, p. 117.] When Mr. Darwin, therefore, brings forward these laws as efficient causes, he not only tacitly admits the inadequacy of his theory to account for the phenomena in question, but he also endeavours to supply the defect by another cause, which, by his own definition, is no cause at all. And further, Mr. Darwin calls in the action of "unknown agencies." [Footnote: Descent of Man, vol. i. p. 154.]
But it may be said, "Is not this the case with all sciences, at least in their earlier stages? Are there not frequently, or always, many phenomena which at first seem inexplicable, but which are gradually accounted for as knowledge increases? If, then, this is no objection in scientific pursuits generally, why should it be so here?" This reasoning would be perfectly valid if Darwinism were regarded simply as a scientific investigation. But it is under consideration now on very different rounds. Whatever Mr. Darwin's own views may be, the theory is brought forward by others, not as a mere interesting speculation, but as antagonistic to a record whose authority is attested by evidence of the very highest class. It claims to discredit that record, and to be received as a substitute for it. But that record, however it may be interpreted, does give us adequate causes for all that it professes to account for, in the will and operation of an Almighty Creator. The theory, therefore, which professes to supplant it, must at least stand upon an equal ground—it must give an adequate account of everything. There must be no unverified laws. To fall back upon such laws is in reality to fall back on the working of that very power whose operation is formally denied. [Footnote: See Foster's Essays, Essay i. Letter 5.]
The next point to be noticed is a great confusion between assumptions and proved facts. This is especially prominent in that part of his last work which is devoted to sexual selection. Thus, in one case it is taken for granted, that various characteristics of the males "serve only to allure or excite the female." [Footnote: Descent of Man, vol. i. p. 258.] "Hence" (because brilliant colours of insects have probably not been acquired FOR THE PURPOSE of protection), "I am led to suppose that the females generally prefer, or are most excited by the more brilliant males." [Footnote: Ibid. p. 399.] "Nevertheless, when we see many males pursuing the same female, we can hardly believe that the pairing is left to blind chance; that the female exerts no choice, and is not influenced by the gorgeous colours, or other ornaments with which the male alone is decorated" [Footnote: Descent of Man, vol. i p. 421.] Such sentences are of continual occurrence, and do duty in the argument as if they expressed ascertained facts. And not only this, but in the very part of the work which is devoted to establishing the adequacy of sexual selection to produce certain effects, that adequacy is assumed from the very beginning. Thus, we read, "That these characters are the result of sexual selection is clear," [Footnote: Ibid. p. 258.] before we have got six pages into an argument which occupies a volume and a half. This is surely a strong instance of what is commonly called "begging the question." Another instance of confusion of ideas is to be found in the assumption of design which occasionally occurs. Thus, we read, "In some other remarkable cases beauty has been gained for the sake of protection, through the imitation of other beautiful species." [Footnote: Ibid. p. 393.] "From these considerations Mr. Bates inferred, that the butterflies which imitate the protected species, had acquired their present marvellously deceptive appearance through variation and natural selection, in order to be mistaken for the protected kinds." [Footnote: Descent of Man, vol. i. p. 411.] In these cases there is an assumption of purpose and design, which, necessarily implies a designer, just as law, treated as an efficient cause, implies a law-giver. It may indeed be that this is only an inaccurate way of expressing something else; but then, such modes of expression are usually the result of a want of clear perception of the ideas to be expressed; and, in this case, such expressions must diminish the weight to be assigned to Mr. Darwin's judgment.