Ape, the name often applied to any monkey, but here confined to the tailless, semi-erect forms that most nearly approach man in structure. This includes the chimpanzee, orang-outang, gorilla and the gibbon. They are all inhabitants of the old world. The term man-like ape applied to these forms is significant of their likeness in structure to man. In fact, man differs structurally from these apes no more than they differ among themselves. It requires some anatomical knowledge to appreciate the differences. Those in the brain are often referred to, but even in that organ it is largely a difference in size, in convolutions and microscopic structure. The convolution containing the brain-cells that preside over speech (convolution of Brocca) is deficient in the apes, and there are, of course, other differences. The likeness is especially strong in the young animal.
An interesting contribution to the facts bearing on the subject of structural resemblances was the finding of a fossil form more man-like than any previously discovered. In 1894, there was found in the island of Java remains of a fossil ape (Pithecanthropus erectus), which, from the capacity and form of the cranium and the anatomy of the long bone of the leg, occupies a position intermediate between man and living apes. The doctrine of evolution does not teach that any existing ape is in the direct line of man's ancestry, but that the simian line and the human line are united in remote generalized ancestors common to both groups. The existing apes are, therefore, side branches, as it were, of the ancestral tree and not in the direct royal line. The apes are progressing in their habits; some of them build rude shelter, use clubs and stones in defense, etc., but a popular misconception should be corrected—their progress is not directly toward humanity, but toward a more perfect simianity. Apes live mainly on vegetable food. They are as large as, or larger than, man; all can walk as man does, though more at home in climbing. They have no tail and no cheek pouches, have great strength and intelligence. They are by nature very savage, and are among the most dangerous of wild animals. See Chimpanzee, Orang-Outang, Gorilla.