Fig. 204—Young orang (Satyrus orang), asleep.
The existing anthropoid apes are only a small remnant of a large family of eastern apes (or Catarrhinæ), from which man was evolved about the end of the Tertiary period. They fall into two geographical groups—the Asiatic and the African anthropoids. In each group we can distinguish two genera. The oldest of these four genera is the gibbon Hylobates, Fig. 203); there are from eight to twelve species of it in the East Indies. I made observations of four of them during my voyage in the East Indies (1901), and had a specimen of the ash-grey gibbon (Hylobates leuciscus) living for several months in the garden of my house in Java. I have described the interesting habits of this ape (regarded by the Malays as the wild descendant of men who had lost their way) in my Malayischen Reisebriefen (chap. xi). Psychologically, he showed a good deal of resemblance to the children of my Malay hosts, with whom he played and formed a very close friendship.
Fig. 205—Wild orang (Dyssatyrus auritius). (From R. Fick and Leutemann.).
The second, larger and stronger, genus of Asiatic anthropoid ape is the orang (Satyrus); he is now found only in the islands of Borneo and Sumatra. Selenka, who has published a very thorough Study of the Development and Cranial Structure of the Anthropoid Apes (1899), distinguishes ten races of the orang, which may, however, also be regarded as “local varieties or species.” They fall into two sub-genera or genera: one group, Dyssatyrus (orang-bentang, Fig. 205), is distinguished for the strength of its limbs, and the formation of very peculiar and salient cheek-pads in the elderly male; these are wanting in the other group, the ordinary orang-outang (Eusatyrus).
Several species have lately been distinguished in the two genera of the black African anthropoid apes (chimpanzee and gorilla). In the genus Anthropithecus (or Anthropopithecus, formerly Troglodytes), the bald-headed chimpanzee, A. calvus (Fig. 206), and the gorilla-like A. mafuca differ very strikingly from the ordinary Anthropithecus niger (Fig. 207), not only in the size and proportion of many parts of the body, but also in the peculiar shape of the head, especially the ears and lips, and in the hair and colour. The controversy that still continues as to whether these different forms of chimpanzee and orang are “merely local varieties” or “true species” is an idle one; as in all such disputes of classifiers there is an utter absence of clear ideas as to what a species really is.