The Evolution of Man, vol 2 - Ernst Haeckel (sight word books .TXT) 📗

(FIGURES 2.278 TO 2.282. Skeletons of man and the four anthropoid apes. (From Huxley.) Cf. Figures 1.203 to 1.209.

FIGURE 2.278. Gibbon (Hylobates).

FIGURE 2.279. Orang (Satyrus).

FIGURE 2.280. Chimpanzee (Anthropithecus).

FIGURE 2.281. Gorilla (Gorilla).

FIGURE 2.282. Man (Homo).)

On the other hand, all the American apes have an additional premolar in each half of the jaw. They have six molars above and below on each side, or thirty-six teeth altogether. This characteristic difference between the eastern and western apes has been so faithfully inherited that it is very instructive for us. It is true that there seems to be an exception in the case of a small family of South American apes. The small silky apes (Arctopitheca or Hapalidae), which include the tamarin (Midas) and the brush-monkey (Jacchus), have only five molars in each half of the jaw (instead of six), and so seem to be nearer to the eastern apes. But it is found, on closer examination, that they have three premolars, like all the western apes, and that only the last molar has been lost. Hence the apparent exception really confirms the above distinction.

Of the other features in which the two groups of apes differ, the structure of the nose is particularly instructive and conspicuous. All the eastern apes have the same type of nose as man—a comparatively narrow partition between the two halves, so that the nostrils run downwards. In some of them the nose protrudes as far as in man, and has the same characteristic structure. We have already alluded to the curious long-nosed apes, which have a long, finely-curved nose. Most of the eastern apes have, it is true, rather flat noses, like, for instance, the white-nosed monkey (Figure 2.276); but the nasal partition is thin and narrow in them all. The American apes have a different type of nose. The partition is very broad and thick at the bottom, and the wings of the nostrils are not developed, so that they point outwards instead of downwards. This difference in the form of the nose is so constantly inherited in both groups that the apes of the New World are called “flat-nosed” (Platyrrhinae), and those of the Old World “narrow-nosed” (Catarrhinae). The bony passage of the ear (at the bottom of which is the tympanum) is short and wide in all the Platyrrhines, but long and narrow in all the Catarrhines; and in man this difference also is significant.

This division of the apes into Platyrrhines and Catarrhines, on the ground of the above hereditary features, is now generally admitted in zoology, and receives strong support from the geographical distribution of the two groups in the east and west. It follows at once, as regards the phylogeny of the apes, that two divergent lines proceeded from the common stem-form of the ape-order in the early Tertiary period, one of which spread over the Old, the other over the New, World. It is certain that all the Platyrrhines come of one stock, and also all the Catarrhines; but the former are phylogenetically older, and must be regarded as the stem-group of the latter.

What can we deduce from this with regard to our own genealogy? Man has just the same characters, the same form of dentition, auditory passage, and nose, as all the Catarrhines; in this he radically differs from the Platyrrhines. We are thus forced to assign him a position among the eastern apes in the order of Primates, or at least place him alongside of them. But it follows that man is a direct blood relative of the apes of the Old World, and can be traced to a common stem-form together with all the Catarrhines. In his whole organisation and in his origin man is a true Catarrhine; he originated in the Old World from an unknown, extinct group of the eastern apes. The apes of the New World, or the Platyrrhines, form a divergent branch of our genealogical tree, and this is only distantly related at its root to the human race. We must assume, of course, that the earliest Eocene apes had the full dentition of the Platyrrhines; hence we may regard this stem-group as a special stage (the twenty-sixth) in our ancestry, and deduce from it (as the twenty-seventh stage) the earliest Catarrhines.

We have now reduced the circle of our nearest relatives to the small and comparatively scanty group that is represented by the suborder of the Catarrhines; and we are in a position to answer the question of man’s place in this suborder, and say whether we can deduce anything further from this position as to our immediate ancestors. In answering this question the comprehensive and able studies that Huxley gives of the comparative anatomy of man and the various Catarrhines in his Man’s Place in Nature are of great assistance to us. It is quite clear from these that the differences between man and the highest Catarrhines (gorilla, chimpanzee, and orang) are in every respect slighter than the corresponding differences between the highest and the lowest Catarrhines (white-nosed monkey, macaco, baboon, etc.). In fact, within the small group of the tailless anthropoid apes the differences between the various genera are not less than the differences between them and man. This is seen by a glance at the skeletons that Huxley has put together (Figures 2.278 to 2.282). Whether we take the skull or the vertebral column or the ribs or the fore or hind limbs, or whether we extend the comparison to the muscles, blood-vessels, brain, placenta, etc., we always reach the same result on impartial examination—that man is not more different from the other Catarrhines than the extreme forms of them (for instance, the gorilla and baboon) differ from each other. We may now, therefore, complete the Huxleian law we have already quoted with the following thesis: “Whatever system of organs we take, a comparison of their modifications in the series of Catarrhines always leads to the same conclusion; the anatomic differences that separate man from the most advanced Catarrhines (orang, gorilla, chimpanzee) are not as great as those that separate the latter from the lowest Catarrhines (white-nosed monkey, macaco, baboon).”

We must, therefore, consider the descent of man from other Catarrhines to be fully proved. Whatever further information on the comparative anatomy and ontogeny of the living Catarrhines we may obtain in the future, it cannot possibly disturb this conclusion. Naturally, our Catarrhine ancestors must have passed through a long series of different forms before the human type was produced. The chief advances that effected this “creation of man,” or his differentiation from the nearest related Catarrhines, were: the adoption of the erect posture and the consequent greater differentiation of the fore and hind limbs, the evolution of articulate speech and its organ, the larynx, and the further development of the brain and its function, the soul; sexual selection had a great influence in this, as Darwin showed in his famous work.

With an eye to these advances we can distinguish at least four important stages in our simian ancestry, which represent prominent points in the historical process of the making of man. We may take, after the Lemurs, the earliest and lowest Platyrrhines of South America, with thirty-six teeth, as the twenty-sixth stage of our genealogy; they were developed from the Lemurs by a peculiar modification of the brain, teeth, nose, and fingers. From these Eocene stem-apes were formed the earliest Catarrhines or eastern apes, with the human dentition (thirty-two teeth), by modification of the nose, lengthening of the bony channel of the ear, and the loss of four premolars. These oldest stem-forms of the whole Catarrhine group were still thickly coated with hair, and had long tails—baboons (Cynopitheca) or tailed apes (Menocerca, Figure 2.276). They lived during the Tertiary period, and are found fossilised in the Miocene. Of the actual tailed apes perhaps the nearest to them are the Semnopitheci.

If we take these Semnopitheci as the twenty-seventh stage in our ancestry, we may put next to them, as the twenty-eighth, the tailless anthropoid apes. This name is given to the most advanced and man-like of the existing Catarrhines. They were developed from the other Catarrhines by losing the tail and part of the hair, and by a higher development of the brain, which found expression in the enormous growth of the skull. Of this remarkable family there are only a few genera to-day, and we have already dealt with them (Chapter 1.15)—the gibbon (Hylobates, Figure 1.203) and orang (Satyrus, Figures 1.204 and 1.205) in South-Eastern Asia and the Archipelago; and the chimpanzee (Anthropithecus, Figures 1.206 and 1.207) and gorilla (Gorilla, Figure 1.208) in Equatorial Africa.

The great interest that every thoughtful man takes in these nearest relatives of ours has found expression recently in a fairly large literature. The most distinguished of these works for impartial treatment of the question of affinity is Robert Hartmann’s little work on The Anthropoid Apes. Hartmann divides the primate order into two families: (1) Primarii (man and the anthropoid apes); and (2) Simianae (true apes, Catarrhines and Platyrrhines). Professor Klaatsch, of Heidelberg, has advanced a different view in his interesting and richly illustrated work on The Origin and Development of the Human Race. This is a substantial supplement to my Anthropogeny, in so far as it gives the chief results of modern research on the early history of man and civilisation. But when Klaatsch declares the descent of man from the apes to be “irrational, narrow-minded, and false,” in the belief that we are thinking of some living species of ape, we must remind him that no competent scientist has ever held so narrow a view. All of us look merely—in the sense of Lamarck and Darwin—to the original unity (admitted by Klaatsch) of the primate stem. This common descent of all the Primates (men, apes, and lemurs) from one primitive stem-form, from which the most far-reaching conclusions follow for the whole of anthropology and philosophy, is admitted by Klaatsch as well as by myself and all other competent zoologists who accept the theory of evolution in general. He says explicitly (page 172): “The three anthropoid apes—gorilla, chimpanzee, and orang—seem to be branches from a common root, and this was not far from that of the gibbon and man.” That is in the main the opinion that I have maintained (especially against Virchow) in a number of works ever since 1866. The hypothetical common ancestor of all the Primates, which must have lived in the earliest Tertiary period (more probably in the Cretaceous), was called by me Archiprimus, Klaatsch now calls it Primatoid. Dubois has proposed the appropriate name of Prothylobates for the common and much younger stem-form of the anthropomorpha (man and the anthropoid apes). The actual Hylobates is nearer to it than the other three existing anthropoids. None of these can be said to be absolutely the most man-like. The gorilla comes next to man in the structure of the hand and foot, the chimpanzee in the chief features of the skull, the orang in brain development, and the gibbon in the formation of the chest. None of these existing anthropoid apes is among the direct ancestors of our race; they are scattered survivors of an ancient branch of the Catarrhines, from which the human race developed in a particular direction.

(FIGURE 2.283. Skull of the fossil ape-man of Java (Pithecanthropus erectus), restored by Eugen Dubois.)

Although man is directly connected with this anthropoid family and originates from it, we may assign an important intermediate form between the Prothylobates and him (the twenty-ninth stage in our ancestry), the ape-men (Pithecanthropi). I gave this name in the History of Creation to the “speechless primitive men” (Alali), which were men in the ordinary sense as far as the general structure is concerned (especially in the differentiation of the limbs), but lacked one of the chief human characteristics, articulate