The human species

by A. de Quatrefages

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.