CHAPTER XI.
ORIGIN OF THE HUMAN SPECIES.—DIFFERENT HYPOTHESES.
I. The preceding chapter might enable me to dispense with a discussion of the applications which have been made of Darwinism to the history of man. Nevertheless, apart from the curious points in the subject itself, some discussion of it will be necessary, for it will not be devoid of instruction.
Lamarck endeavoured to show how, by means of his theory of habit, it was possible to conceive the direct transmutation of the chimpanzee into man. The Darwinists also agree in connecting man with the apes. Nevertheless none of them point out any of the species at present existing as our immediate ancestor; on this point they differ from their illustrious predecessor. It might be supposed that Vogt had determined this point if we take literally some passages of his Leçons sur l’homme. But the Genevese savant has clearly expressed his theory in his Mémoire sur les Microcéphales. He carries back the point of departure common to the two types to an anterior ancestor. Darwin, Wallace, Filippi, Lubbock, Haeckel, etc., connect man still more closely with the apes. The latter states his conclusions in the following terms:—
“The human race is a branch of the catarrhine group; he was developed in the old world, and sprang from apes of this group, which have long been extinct.”
II. Vogt disagrees with his scientific colleagues in an important point. He admits that different simian stocks may have given rise to different human groups. The populations of the old and the new world would thus be descendants of the different forms which are peculiar to the two continents. On this hypothesis, Australia and Polynesia, where there never have been apes, must necessarily have been peopled by means of migration.
The eminent professor of Geneva, moreover, always confines himself to a somewhat vague statement of his ideas relative to the genealogies which he thinks fit to attribute to the different groups of mankind.
III. Darwin and Haeckel have been bolder. The former has published an important work upon the Descent of Man, and the latter in his History of the Creation of Organised Beings has treated the same subject in detail, and given the genealogical table of our supposed ancestors, starting from the most simple known animals. The master and the disciple agree almost invariably, and it is to Haeckel himself that Darwin refers the reader who is curious to know the human genealogy in detail. Let us glance rapidly at the origin assigned to us by the German naturalist.
Haeckel considers as the first ancestor of all living beings the monera, which are nothing more than the amœbæ as understood by Dujardin. From this initial form man has reached the state in which we now find him, by passing through twenty-one typical transitory forms. In the present state of things our nearest neighbours are the anthropomorphous or tailless catarrhine apes, such as the orang, the gorilla, the chimpanzee, etc. All are sprung from the same stock, from the type of the tailed catarrhine apes, the latter are descended from the prosimiæ, a type which is now represented by the macaucos, the loris, etc. Next come the marsupials, which form the 17th stage of our evolution; further examination is useless.
Although the distance between anthropomorphous apes and man appears to be but small to Haeckel, he has nevertheless thought it necessary to admit the existence of an intermediate stage between ourselves and the most highly developed ape. This purely hypothetical being, of which not the slightest vestige has been found, is supposed to be detached from the tailless catarrhine apes, and to constitute the 21st stage of the modification which has led to the human form, Haeckel calls it the ape-man, or the pithecoid man. He denies him the gift of articulate speech as well as the development of the intelligence and self-consciousness.
Darwin also admits the existence of this link between man and apes. He says nothing as to his intellectual faculties. On the other hand he traces out his physical portrait, basing his remarks upon a certain number of exceptional peculiarities observed in the human species, which he regards as so many phenomena of partial atavism. “The earliest ancestors of man,” he says, “were without doubt once covered with hair; both sexes having beards; their ears were pointed and capable of movement; and their bodies were provided with a tail having the proper muscles. Their limbs and bodies were acted on by many muscles, which now only occasionally reappear in man, but which are still normally present in the quadrumana. The great artery and nerve of the humerus ran through a supracondyloid foramen. At this, or some earlier period, the intestine gave forth a much larger diverticulum or cœcum than that now existing. The foot, judging from the condition of the great toe in the fœtus, was then prehensile, and our progenitors, no doubt, were arboreal in their habits, frequenting some warm forest-clad land; the males were provided with canine teeth which served as formidable weapons.”
IV. In attributing a tail to our first direct ancestors Darwin connects him with the type of tailed catarrhines, and consequently removes him a stage backward in the scale of evolutions. The English naturalist is not satisfied to take his stand upon the ground of his own doctrines, and, like Haeckel, on this point places himself in direct variance with one of the fundamental laws which constitute the principal charms of Darwinism, whose force I am far from denying.
In fact, in the theory of Darwin, transmutations do not take place, either by chance or in every direction. They are ruled by certain laws which are due to the organisation itself. If an organism is once modified in a given direction, it can undergo secondary or tertiary transmutations, but will still preserve the impress of the original. It is the law of permanent characterisation which alone permits Darwin to explain the filiation of groups, their characteristics and their numerous relations. It is by virtue of this law that all the descendants of the first mollusc have been molluscs; all the descendants of the first vertebrate have been vertebrates. It is clear that this constitutes one of the foundations of the doctrine.
It follows that two beings belonging to two distinct types can be referred to a common ancestor, whose characters were not clearly developed, but the one cannot be the descendant of the other.
Now man and apes present a very striking contrast in respect to type. Their organs, as I have already remarked, correspond almost exactly term for term; but these organs are arranged after a very different plan. In man they are so arranged that he is essentially a walker, while in apes they necessitate his being a climber just as strongly.
There is here an anatomical and mechanical distinction which had already been proved, as regards the inferior apes, by the works of Vicq d’Azyr, Lawrence, Serres, etc. The investigations of Duvernoy on the gorilla, of Gratiolet and M. d’Alix upon the chimpanzee, have established the fact that the anthropomorphous apes possess the same fundamental character in every point. Moreover, a glance at the page where Huxley has figured side by side a human skeleton and the skeletons of the most highly developed apes, is a sufficiently convincing proof of the fact.
The consequence of these facts, from the point of view of the logical application of the law of permanent characterisation, is that man cannot be descended from an ancestor who is already characterised as an ape, any more than a catarrhine tailless ape can be descended from a tailed catarrhine. A walking animal cannot be descended from a climbing one. This was clearly understood by Vogt. In placing man among the primates he declares, without hesitation, that the lowest class of apes have passed the landmark (the common ancestor) from which the different types of this family have originated and diverged.
We must then place the origin of man beyond the last ape if we wish to adhere to one of the laws most emphatically necessary to the Darwinian theory. We then come to the prosimiæ of Haeckel, the loris, indris, etc. But these animals also are climbers; we must go further, therefore, in search of our first direct ancestor. But the genealogy traced by Haeckel brings us from the latter to the marsupials.
From man to the kangaroo the distance is certainly great. Now neither living nor extinct fauna show the intermediate types which ought to serve as land-marks. This difficulty causes but slight embarrassment to Darwin. We know that he considers the want of information upon similar questions as a proof in his favour. Haeckel doubtless is just as little embarrassed. He admits the existence of an absolutely theoretical pithecoid man, and it is not the only instance in which he proceeds in a similar manner in order to complete his genealogical table. Take as an instance his words upon the sozoura (14th stage), an amphibious animal which is equally unknown to science. “The proof of its existence arises from the necessity of an intermediate type between the 13th and the 14th stage.”
Thus, since it has been proved that, according to Darwinism itself, the origin of man must be placed beyond the 18th stage, and since it becomes, in consequence necessary to fill up the gap between marsupials and man, will Haeckel admit the existence of four unknown intermediate groups, instead of one? Will be complete his genealogy in this manner? It is not for me to answer.
V. Darwin and Haeckel will most certainly think it very strange that a representative of the old school, a man who believes in the reality of species, should have the pretension to be better acquainted with the application of the laws of Darwinism than themselves, and to point out serious lapses in the applications they have made. Let us take our stand then on the ground of facts. There we shall at once find proof that this genealogy is wrong throughout, and is founded on a material anatomical error.
Both Darwin and Haeckel connect the simian series with a type which would now be represented by the lemuridæ, which the latter designates by the term prosimiæ. The only grounds which Darwin assigns for this opinion are certain characters taken especially from dentition. Haeckel goes back to embryogenesis.
We know that with the exception of the marsupials (kangaroos, sarrigue), and the monotremata (ornithorhynchus, echidna), all mammals have a placenta, an organ essentially composed of a network of blood-vessels, which unites the mother to the fœtus, and serves for the nutrition of the latter. With the ruminants, the edentata, and the cetacea, the placenta is simple and diffuse, that is to say, the tufts of the blood-vessels are developed upon the entire surface of the fœtal envelope, and are in direct communication with the inner surface of the uterus. In the rest of the mammals the placenta is double; half being derived from the mother, and half from the fœtus, or rather its external envelope. A special membrane called the Decidua covers the interior of the uterus, and unites the placentæ. Haeckel, correctly attaching great importance to these anatomical differences, divides mammals into two great groups: the indeciduata, which have no decidua, and the deciduata, which possess it.
Among the latter the placenta can surround the mammalian ovum like a girdle (zonoplacentalia), or form a kind of circular disc more or less developed (discoplacentalia). Man, apes, bats, insectivora, and rodents, present the latter arrangement, and thus form a natural group to which no zonoplacential, and, of course, no indeciduate mammals can be admitted.
Haeckel, without the least hesitation, adds his prosimiæ to the groups which I have just enumerated, that is to say, he attributes to them a decidua and a discoidal placenta. Now the anatomical investigations of MM. Alphonse Milne Edwards and Grandidier upon the animals brought by the latter from Madagascar place it beyond all doubt that the prosimiæ of Haeckel have no decidua and a diffuse placenta. They are indeciduata. Far from any possibility of their being the ancestors of the apes, according to the principle laid down by Haeckel himself, they cannot even be regarded as the ancestors of the zonoplacential mammals, the carnivora for instance, and ought to be connected with the pachydermata, the edentata and the cetacea.
Darwin and Haeckel will, perhaps reply that when they made their genealogies, the embryogenesis of the prosimiæ was not known. But why then represent them as one of the intermediate links to which they attach so much importance? Their process is always the same, considering the unknown as a proof in favour of their theory.
VI. The necessity, which I think has been clearly proved, of seeking elsewhere than among the prosimiæ for the link which is required between the marsupials and the apes, would not invalidate the relationship between the latter and man. There are, however, other facts which are irreconcilable with the theory.
M. Pruner Bey, resuming the descriptive and anatomical works which have been carried on till within the last few years, has shown that the comparison of man with the anthropomorphous apes brings to light a fact which is subject to very few exceptions, the existence, namely, of an inverse order in the development of the principal organs. The researches of Welker upon the sphenoïdal angle of Virchow lead to the same conclusion, for in man the angle diminishes from the time of birth, whilst in the ape it is always increasing, so much so that sometimes it is effaced. It is upon the base of the cranium that the German anatomist has remarked this inverse order, the importance of which cannot escape notice.
A similar contrast has been remarked by Gratiolet upon the brain itself. The following are his observations upon this subject. In the ape the temporal sphenoïdal convolutions, which form the middle lobe, make their appearance and are completed before the anterior convolutions which form the frontal lobe. In man, on the contrary, the frontal convolutions are the first to appear, and those of the middle lobe are formed later.
It is evident, especially after the most fundamental principles of Darwinism, that an organised being cannot be a descendant of another whose development is in an inverse order to its own. Consequently, in accordance with these principles, man cannot be considered as the descendant of any simian type whatever.
VII. I have said above that palæontology has never shown anything which recalls in the slightest degree the hypothetical pithecoid man of Haeckel. A hope was felt that what could not be found among extinct forms might be found among living ones. Vogt has compared the brain of microcephali to that of the anthropomorphous apes, and Haeckel has represented in his genealogical table of idiots, crétins and microcephali as actual representatives of his speechless man. These beings, with their small brain and incomplete faculties, are, according to these two naturalists, cases of atavism, and recall the normal state of our most remote direct ancestors.
Here we have another instance of the curious method of reasoning familiar to Darwinists. Microcephalism, idiotcy, and crétinism constitute so many teratological or pathological states. They belong, consequently, to the very numerous groups of facts which have long been studied. If some of these facts can be regarded as phenomena of atavism, why should it be otherwise with the rest? Why attribute to atavism a single character only in crétins and microcephali, and refer the other to teratology and pathology? This is evidently an entirely arbitrary kind of treatment, and as much opposed as possible to the true scientific method.
After the works of teratologists, after the experiments of Geoffroy, so ably resumed and completed by M. Dareste, the part played by pathogenic causes, even by external causes, in arrested development cannot be denied. Now microcephalism is nothing else than arrested development acting on the cranium and its contents. But this is not an isolated case. Other organs and functions in microcephali suffer in the same manner. They have been proved to be always sterile, and certainly sterility is not a phenomenon which can be referred to atavism.
Thus among microcephali a teratogenic cause is clearly proved to have acted on part of the organism, viz., the generative organs. What reason can be alleged for attributing alterations of the cranium and brain to an entirely different cause? By virtue of what principle can two facts be separated, which observation has shown to be so intimately connected with each other? Why should the first be appealed to as an argument and nothing said about the second? Is it not evident that this is an entirely arbitrary kind of procedure, and actuated solely by the requirements of theory?
The general plan of the brain is fundamentally the same in all the mammalia and in man. Upon this point, as upon every other, the resemblance is greatest when the latter is compared with the anthropomorphous apes. When, for some reason or other, his brain is altered and reduced, as in the microcephali, is it at all surprising that fresh resemblances should arise. The contrary would be unintelligible.
This is a fact upon which Vogt has especially insisted, and he has described from this point of view several interesting details which render less general some of the results obtained by M. Gratiolet. But it is a remarkable fact that these new relations are not established with the most highly developed apes, but with the tailed apes of the new world, with the platyrrhini, which are excluded by Haeckel and Darwin from the human ancestral series. Thus, the Darwinian theory itself protests against the comparison between the microcephali and our pretended pithecoid ancestors.
The relations which we are discussing do not, moreover, reach a similarity which would authorise the conclusions of the Genevese savant. The brains of microcephali, though often less voluminous and less convoluted than those of the anthropoid apes, according to Gratiolet, do not become at all similar to them. This proposition is confirmed by the work of Vogt.
The case is the same with the skeleton as with the brain. I will here appeal to an authority, which none of my adversaries can reject, that, namely, of Huxley. After having protested against the statements of those who declare “that the structural differences between man and apes are small and insignificant,” the eminent anatomist adds that “every bone of the gorilla bears a mark by which it can be distinguished from the corresponding human bone, and that, in the present state of creation at least, no intermediary being fills the gap which separates man from the troglodyte.” In the general conclusion of his book, Huxley moreover recognises the fact that the fossil human remains hitherto discovered do not indicate any approach towards the pithecoid form.
VIII. After the formal declarations of a naturalist, whose Darwinian convictions place him beyond all suspicion of partiality, how is it that we continually find the expression simian character employed à propos of the most insignificant modifications of some human type of which no one gives a precise description? It is, to say the least, an abuse of words, against which I have often protested. We have just seen that this expression assumes an anatomical fact which does not exist, and which, consequently, constitutes an error. It has, moreover, the inconvenience of being understood literally by the ignorant, and sometimes of deceiving even educated men, and of giving rise to a belief in imaginary degradations and comparisons.
In fact, man and the rest of the vertebrata are constructed upon the same fundamental plan. Between him and the other members of this group numerous relations exist. Organised beings are not crystals whose forms are mathematically defined; with the former the whole of the body and each part of this whole oscillate between limits whose extent has not yet been fixed, but which is at times considerable. By these very oscillations the customary relations are continually modified, not only between man and the apes, but between man and the rest of the vertebrata. If we compare man to any animal type whatever, if we apply the same method to this comparison, and the same terminology, we shall arrive at singular conclusions. I will quote a single example.
The most important fact in connection with the brain is certainly not its absolute development. It is the relation of this development to that of the rest of the body. The agreement upon this point, when animals are the subject of discussion, is general. It should be the same when the discussion is on man. Undoubtedly upon this ground of relative superiority or inferiority, upon which certain anthropologists so readily take their stand à propos of races or individuals, the relations of which I speak constitute one of the most striking and essential characters.
I subjoin some of these relations taken from a table of Duvernoy, and in which the weight of the brain is taken as unity.