British Quarterly Review, American Edition, Vol. LIV / July and October, 1871

by Various

It has been shown that certain structural characteristics observable to the unaided eye are common to man and the lower animals, and this fact has been urged in favour of the conclusion adopted by Mr. Darwin. Thus, great stress is laid upon the presence of 'the little blunt point projecting from the inwardly folded margin or helix of the ear of man.' This is decided to be the vestige of the formerly pointed ears of the progenitors of our predecessors with arboreal habits, but nothing is said in explanation of the complete absence of rudiments of parts which we should expect to find. And surely there may be differences of opinion as to the bearing of many of the facts advanced, although Mr. Darwin affirms that their bearing is unmistakable. The observation that, 'on any other view, the similarity of pattern between the hand of a man or monkey, the foot of a horse, the flipper of a seal, the wing of a bat, &c., is utterly inexplicable,' is not complimentary to the ingenuity or conjectural capacity of those who are to succeed Mr. Darwin; but to assert that these parts have been formed on the same ideal plan is not a scientific explanation; it is merely to express an opinion in a very arbitrary and rather abrupt manner. It may be 'natural prejudice' and it may be 'arrogance' which leads some to demur to the conclusions deduced by Mr. Darwin and his friends, and the prophecy[63] at the end of his chapter may be fulfilled, but it is at any rate premature; while it is by no means fair to imply that every naturalist who refuses to accept Mr. Darwin's hypothesis believes that each mammal and man 'was the work of a separate act of creation.'

As is well known, there are certain diseases which may be communicated from man to the lower animals, or from the lower animals to man, and Mr. Darwin tells us that the fact 'proves (!) the close similarity of their tissues and blood, both in minute structure and composition.' Here, again, in what he regards as his proof, Mr. Darwin begs the question. Such premises afford no justification whatever for the conclusion arrived at, while the force of the remark depends entirely upon the meaning attached to the phrase 'close similarity.' We may assert with truth that there is a very close similarity between the blood of a rat and the blood of a Guinea pig, and also that the blood of the rat differs widely from that of the Guinea pig. In the first assertion, 'close similarity' is used in a sense which does not imply that 'widely different' is not equally true of the statement to which it relates. The argument adopted by Mr. Darwin is not an argument in favour of his conclusion. He might urge with equal force that since bacteria grow and multiply in many different fluids and solids, these fluids and solids exhibit a close similarity in structure and composition; or, conversely, it might be held, that because certain poisons produce very different effects upon the nerve-tissues of different animals, therefore the nerve-tissues of these animals must differ widely in minute structure and chemical composition.

As regards the statements that man and animals alike die of apoplexy, suffer from fever, are subject to cataract, take tea, are fond of tobacco, and the like, it is simply astounding that Mr. Darwin should have advanced them with the view of strengthening his case. The circumstance almost leads us to infer that he was not altogether unconscious of the weakness of his own cause. He has been over-sanguine regarding his powers of convincing his readers of the truth of any proposition he might think fit to advance. It would have been more to the purpose to have maintained that, since all mammals have blood and blood-vessels, brains, and nerves, it is certain that all mammals must have had a common origin, since it is not possible to account for the close similarity between these tissues in any other way.

Nor is it easy to understand how the community-of-origin hypothesis is assisted by the fact that man and animals are infested by parasites, seeing that the parasites are as different from one another as are the species which they infest, and, like the latter, are incapable of interbreeding, and exhibit specific distinctions of the most striking kind.

That reproduction and gestation are carried out upon the same general plan in all mammals is universally known, but it is straining argument with a vengeance to advance this in favour of their community of origin, considering the marvellous variations in detail which are observed in respect of these processes in different and even in very closely allied mammals.

The fact that man arrives at maturity more slowly than other animals is met by Mr. Darwin with the cautious observation that 'the orang is believed not to be adult till the age of from ten to fifteen years.' This is by no means a solitary example of the very vague observations which Mr. Darwin admits as data upon which to ground his conclusions. For want of more demonstrative evidence, he is constrained to accept the loose statement to which we have alluded; and it must be admitted that he has displayed considerable ingenuity in making the most of the utterly inconclusive and sometimes unreliable material at his disposal; but it is indeed very remarkable that he should consider himself in any way justified by the facts and arguments to which he has adverted, in summing up so very definitely and so very decidedly as he has done on the sixth page of the first chapter of his book. The italics in the following sentence are our own: 'It is, in short, scarcely possible to exaggerate the close correspondence in general structure, in the minute structure of the tissues, in chemical composition, and in constitution, between man and the higher animals, especially the anthropomorphous apes!'

Mr. Darwin adduces another argument in his favor from embryonic development, and proceeds to show that at a certain period the human embryo is very like that of the dog. He quotes with approval the remark of Mr. Huxley, that as regards development man is 'far nearer to apes than the apes are to the dog;' but if we suppose the resemblance to be far greater than is really the case, it is difficult to see how the fact would strengthen the hypothesis in favour of which it is advanced. Because the embryo of a dog resembles that of a man, therefore both were derived from a common progenitor, seems a very curious specimen of reasoning, and implies the acceptance of a number of other propositions which have been and will continue to be disputed. We are assured that no other explanation than the one advanced by Mr. Darwin 'has ever been given of the marvellous fact that the embryos of a man, dog, seal, bat, reptile, &c., cannot at first be distinguished from each other;' but as needs scarcely be said, this circumstance adds no weight to the particular explanation in question, and does not increase the probability of its being proved to be true at some future day. According to Mr. Darwin, we ought frankly to admit the force of every argument he thinks fit to advance; but surely, before doing so, there is no harm in examining the facts a little more closely. And, first, it would have been desirable to inquire whether the resemblance was really as great as a superficial examination by the unaided eye seemed to indicate; next, it should have been ascertained whether the differences between the animal and the human embryo were not also very considerable; in which case it would have been necessary to inquire further concerning the bearing of the differences demonstrated, upon the hypothesis of the community of origin of the several embryos, grounded upon the likeness.

But Mr. Darwin does not tell us why he selected one particular period of development for demonstrating the resemblance between the human embryo and that of the dog. The likeness was in truth much greater at a period still earlier than the one selected. Nay, the fact must be known to Mr. Darwin, that at a very early stage in development we fail to discover, after the most careful scrutiny, any difference between the matter which, under certain conditions, will become man, and that which, under certain other conditions, will become dog, or cat, or bird, or frog, or jelly-fish, or plant; yet it would be monstrous to assert that apparent likeness was real identity. It is only during the later stages of development, as Mr. Huxley affirms, and as has been well known for fifty years or more, that 'the young human being presents marked differences from the young ape.' But why is the reader not told that at a very early period of development these embryos are not only like one another, but could not by any means at our disposal be distinguished from each other or from any other form of embryo matter in nature? The results of the act of living in the two cases are very different, but the living matter itself seems to be nearly identical. The material out of which man is evolved is perhaps exactly like that from which every other vertebrate living being proceeds, and it does not differ in any ascertained points from that from which the most destructive morbid growths may be developed. Here, then, is an argument for the community of origin of everything in nature. Not only is man's brain developed like the dog's brain, but the matter in which every one of his organs originates is like that from which every other tissue in nature is evolved.

But when we come to examine more minutely the tissues of the embryo man and the embryo dog at about the period of development selected by Mr. Darwin for comparison, we find very remarkable points of difference in their minute structure. If we examine particular tissues by the aid of high microscopic powers, we shall discover points of difference as well as points in which they agree, and this at every stage of growth subsequent to the time when the tissues have acquired their special characters. If, then, from the fact of general resemblance we are to argue in favour of a common origin, what explanation have we to offer of the peculiar and constant, though definite differences between the corresponding tissues of different animals at corresponding periods of development? Mr. Darwin's explanation may account for the resemblance between the different embryos at a particular period of development, but it does not help us in the least to understand why there should be differences in the ultimate structure of the tissues at this same period, any more than it explains the still more remarkable resemblance between different forms of embryonic matter at every period of life, in health and in disease.

It is difficult to understand how 'natural selection' can work, unless we admit that the matter of the germ possesses the property of undergoing modification. But if modifying power determines the changes, this must itself be referred to something inherent in the matter of the germ itself—a primary power of the organism transmitted from pre-existing organisms. Such a power is, however, inadmissible in any evolutional hypothesis, and so far from being explained by natural selection, explains the facts grouped under that head. It is true that Mr. Darwin does admit the operation of 'unknown agencies' influencing the nature and constitution of the organism, but he adduces no reason for supposing that these unknown agencies will be discovered at some future time, or that they are in any way dependent on natural selection. If we require 'unknown agencies' at all, we may surely dispense with natural selection altogether, and attribute the formation of species to these unknown agencies directly, instead of attributing it to natural selection and referring natural selection to the unknown agencies.