Creation or Evolution? A Philosophical Inquiry

by George Ticknor Curtis

Of direct evidence of this evolution of species, it can not be said that we have any which will make it a parallel case with the direct evidence of the descent of an individual from parents and other ancestors. We have different animal organisms that are marked by distinctions which compel us to regard them as separate species, and there is no known instance in which we can directly trace a production of one of these distinct species out of another or others by finding a connection of lives with lives. Even in the vegetable kingdom, with all the crosses for which Nature has made such wonderful and various provision, we do not find such occurrences as the production of an oak out of the seed of an apple, or the production of an orange-tree out of an acorn. We do not gather grapes of thorns or figs of thistles. There are barriers set to miscegenation even in the vegetable world, and we have no direct evidence that at any period in the geological history of the earth these barriers have been crossed, and very little indirect evidence to warrant us in believing that they ever have been or ever will be. In the animal kingdom such barriers are extremely prominent and certain. We not only have no direct evidence that any one species of animal was at any period of the earth's history or in any length of time gradually evolved out of another distinct species, but we know that the union of the sexes and the production of new individuals can not take place out of certain limits; that, while Nature will permit of the crossing of different breeds of the same animal, and so will admit of very limited variations of structure, she will not admit of the sexual union of different species, so as to produce individuals having a union of the different organisms, or a resultant of a third organism of a different type from any that had preceded it. Is it, for example, from mere taste or moral feeling that such occurrences as the sexual union between man and beast have not been known to have produced a third and different animal? We know that it is because the Almighty has "fixed his canon" against such a union in the case of man and in the cases of all the other distinct animal organisms; and to find this canon we do not need to go to Scripture or revelation, although we may find it there also.

We are remitted, therefore, to indirect evidence, and in considering this evidence we have to note that we have nothing but an imaginary pedigree, or one hypothetically constructed, to which to apply it. In tracing the pedigree of an individual animal, we have a certain number of known connections of life with life; and where it becomes necessary to bridge over a break in the connection so as to carry the line back to an earlier ancestor, we may perhaps apply the collateral evidence of family or race resemblance to assist in making the connection with that particular ancestor a reasonably safe deduction. But in the case of the hypothetical pedigree which supposes the human race to have been evolved from a single cell through successive organisms rising higher and higher in the scale of being, we have no known connections of lives with lives to which to apply the collateral proofs. The collateral proofs are not auxiliary evidence; they are the sole evidence; and unless they are such as to exclude every other reasonable explanation of the phenomena which they exhibit excepting that of the supposed evolution, they can not be said to satisfy the rules of rational belief in the hypothesis to which we apply them.

What, then, is the indirect and collateral evidence? It consists, as we have already seen, of two principal classes of phenomena: first, resemblances of fœtal development which are found on comparing the fœtal growth of different species of animals; second, resemblances in the structure of different species of animals after birth and maturity. These various resemblances are supposed to constitute proof of descent from a common stock, which may be carried back in the series as far as the resemblance can be carried, at whatever point that may be. Thus, in comparing all the vertebrata, we find certain marked peculiarities of structure common to the whole class: the deduction is, that all the vertebrate animals came from a common stock. In comparing all the mammalia, we find certain marked peculiarities of structure common to the whole class: the deduction is that all the mammalia came from a common stock. Going still further back in the supposed series, we come to the amphibians, as the supposed common stock from which the vertebrate and mammalian land animals were derived; and, comparing the different classes of the amphibians, we find certain resemblances which point to the fish inhabitants of the water as their common stock; and then we trace the more highly organized fishes through the more lowly organized back to the aquatic worm, which may itself be supposed to have been developed out of a single cell.[75]

The resemblances of structure, wherever we make the comparison between different species, are referable to an ideal plan of animal construction, followed throughout a class of animals, and adjusted to their peculiar differences which distinguish one species from another, just as in the vegetable world there is an ideal plan of construction of trees followed throughout a class of plants, and adjusted to the peculiar differences which distinguish one kind of tree from another. As between man and the monkey, or between man and the horse, or the seal, or the bat, or the bird, there are certain resemblances in the structure of the skeleton, which indicate an identity of plan, although varied in its adjustments to the distinguishing structure of each separate species of animal. In a former chapter, I have shown why the adoption of an ideal plan of a general character is consistent with what I have called the "economy of Nature" in the special creation of different species. On a careful revision of the subject, I can see no reason to change the expression, or to modify the idea which it was intended to convey, and which I will here repeat. It is entirely consistent with the conception of an infinite and all-wise creating power, to suppose that in the formation of a large class of organisms, all the constructive power that was needed for the formation of a general plan was exercised throughout the class, and that there was super added the exercise of all the power of variation that was needful to produce distinct species. Repetition of the same general plan of construction is certainly no mark of inferiority of original power, if accompanied by adaptations to new and further conditions. It is a proof that in one direction all the necessary power was used, and no more, and that in producing the distinct organisms the necessary amount of further power was also used. If we follow the resemblances of structure that may be traced through all the animals of a varied class, we shall find that they may be referred, as a rational and consistent hypothesis, to this method of giving to each animal its characteristic formation. If this is a rational hypothesis, it is so because it is consistent with all the observable phenomena; and consequently, the opposite hypothesis that all these phenomena of resemblances and differences are due to the law of evolution does not exclude every other explanation of their existence.

To apply this now to one of the comparisons on which great stress is laid—the comparison between the brain of man and that of the ape. Two questions arise in this comparison: 1. Do the resemblances necessarily show that these two animals came from a common stock? 2. Do the resemblances necessarily show that man was descended from some ape through intermediate animals by gradual transformations? And, when I ask whether the comparison necessarily leads to these conclusions, I mean to ask whether the resemblances point so strongly to the conclusions that they must rationally be held to exclude every other hypothesis.

Prof. Huxley furnished to Mr. Darwin a very learned note, in which he stated the results of all that is now known concerning the resemblances and differences in the structure and the development of the brain in man and the apes. The differences may be laid aside in the present discussion, because it is not necessary, for my present purpose, to found anything upon them. But the resemblances, just as they are stated by the eminent anatomist, without regard to controverted details, are the important facts to be considered. The substance of the whole comparison is that the cerebral hemispheres in man and the higher apes are disposed after the very same pattern in him as in them; that every principal "gyrus" and "sulcus" of a chimpanzee's brain is clearly represented in that of a man, so that the terminology which applies to one answers for the other; that there is no dispute as to the resemblance in fundamental character between the ape's brain and man's; and that even the details of the arrangement of the "gyri" and "sulci" of the cerebral hemispheres present a wonderfully close similarity between the chimpanzee, orang, and man.[76] These are said to be the result of a comparison of the adult brain of man and the higher apes; and, although it is claimed by some anatomists that there are fundamental differences in the mode of their development which point to a difference of origin, this is denied by Huxley, who maintains that there is a fundamental agreement in the development of the brain in man and apes. His views of the facts for the purpose of the present inquiry may be accepted without controversy, not only because he is an authority whose statements of facts I am not disposed to dispute, but because it is not necessary to dispute them. What, then, do they show?

They show that there are animals known as apes and animals known as men, whose brains are found to be fundamentally constructed upon the same general plan, with strong resemblances throughout the different parts of the organ; and the first question is, Do these resemblances show that the two animals came from a common stock? Upon the theory that man has resulted from the gradual modifications of the same form as that from which the apes have sprung, the resemblances in the structure of their respective brains are claimed as having a tendency to show that there was an animal which preceded both of them, and which was their common ancestor, in the same sense in which an individual progenitor was the common ancestor of two other individuals, whether one of these two individuals was or was not descended from the other in a direct line. On the other hand, upon the hypothesis of the special creation of the ape as one animal, and the special creation of man as another animal, there was no common stock from which the two animals have been derived, and the resemblances of their brains point to the adoption of a general plan of construction for that organ, or its construction upon the same model, and the adaptation of that model to the other parts of the structure, and the purposes of the existence of each of the two animals. Without again repeating the argument which shows that the latter hypothesis is perfectly consistent with the professed conception of the infinite power, I will now inquire whether, on the former hypothesis, we have anything to which we can apply the evidence of resemblance as a collateral aid in reaching the conclusion that these two animals were derived from a common progenitor, or from some antecedent animal whose brain and other parts of the structure became modified into theirs by numerous intermediate gradations.

Between the higher apes, or between any of the apes and any known antecedent and different animal, no naturalist has discovered the intermediate link or links. Darwin supposes that there was some one extremely ancient progenitor from which proceeded the two main divisions of the Simiadæ—namely, the Catarrhine and Platyrhine monkeys, with their sub-groups. This extremely ancient progenitor is nothing but a scientific hypothesis; or, to use a legal phrase, it had nothing but a constructive existence. It is necessary to believe in the principle of evolution, in order to work out the hypothesis of this creature from which the two great stems of the Simiadæ are supposed to have proceeded. Here, then, we have the case of a pedigree or succession of animal races, the propositum of which has no known existence. Next we have two known divisions of the Simiadæ, or monkeys; but, between them and their imaginary common progenitor, we have no known intermediate animals constituting the gradations of structure from the progenitor to the descendants. The whole chain has to be made out by tracing resemblances among the animals of a certain class that are known, then applying these resemblances to the supposed divergencies from the structure of a supposed progenitor, and then drawing the conclusion that there was such a progenitor. It may be submitted to the common sense of mankind, whether this is a state of facts which will warrant scientists or philosophers in using toward those who do not accept their theory quite so much of the de haut en bas style of remark as we find in the writings of Mr. Spencer.[77] If the researches of geologists had ever discovered any remains of an animal that would fulfill the requirements, and thus stand as the progenitor of the Simiadæ. By the case would correspond to that of a known individual from whom we undertake to trace the descent of another individual through many intermediates; and in such a case strong family resemblances of various kinds might possibly afford some aid in making out the pedigree as a reliable conclusion. But there is no means of connecting the Old World and the New World apes with any but an unknown and imaginary, progenitor. Darwin himself frankly tells us that "the early progenitor of the whole Simian stock, including man," is an undiscovered animal, which may not have been identical with, or may not even have closely resembled, any existing ape or monkey.[78]