The great apes (Pongidae) are not nearly as human as is sometimes supposed and as the problem-solving powers of the chimpanzee might indicate. Physically they are very different.

Their great weight has brought them to the lower branches of the trees and to the ground, and they walk rather than run on all fours, using their forelimbs as crutches, knuckles down. The feet have lost their mobility and some of their prehensility. The spine is massive and rigid, the shoulders broad, the chest barrel-shaped and the arms enormously long. Their tails have been entirely lost and their legs are short.

The heavy chewing and neck muscles are attached to remarkable bony ridges along the top of the skull. The canine teeth are well developed and the jaw pattern rather rectangular, whereas that of man is semicircular. Their brains are well developed, though far below those of Homo erectus.

We thus see that a considerable degree of specialization has taken place, from which there can be no return.

No evolution of the apes in the direction of man is now possible. It is even correct to say that man is in many respects closer to the monkeys than he is to the apes, especially with regard to the generalized proportion of the hands, the development of the thumb, the leg and foot muscles, the sequence of eruption of the middle teeth, the tendency towards late obliteration of the cranial sutures, and in the absence of a curious long shelf just underneath the front of the jaw (also absent in Proconsul). From this it would appear that the stock from which the hominids arose was monkey-like rather than ape-like.