The hominoids include both the ape line—the Pongidae—and the line leading to man—the Hominidae. The Pongidae are represented today by the great apes— the chimpanzee, the gorilla and the orang-utang. The Hominidae include the fossil Australopithecus, fossil man, now extinct, and living man—Homo sapiens.  Although this advance first took place in the New World, there was no further progress in this hemisphere beyond the level of the New World monkeys. But in the Old World this new type developed not only into the Old World monkeys, but gave rise to a progressive branch which advanced from the pithecoid or monkey stage to the hominoid stage. This is 'man-like' and includes the gibbons, the great apes and man today.

It is now believed by a number of investigators that this original, unspecialized, monkey-like type gave rise not to one hominoid line which divided into men and apes at a very late stage, but into two main streams: the Pongidae, leading to the great apes, and the Hominidae leading to man. As long ago as the Oligocene there is evidence of these two divergent types of hominoid.

It was for a long time believed that the divergence took place only 14 million years ago or thereabouts, and that a Miocene African ape, Proconsul, which was relatively unspecialized and had not developed. the anatomical modifications for swinging in trees known as brachiation, was the common ancestor of men and apes.

More recent theories classify Proconsul as belonging to a most interesting and widely dispersed genus of tree-apes known as Dryopithecus, which was the culmination of the pongid line and which separated from the hominids 20 million years before Proconsul. It is thought that Proconsul or a similar type may have given rise to the chimpanzee and gorilla, and that another type of Dryopithecus may have been the ancestor of the orang-utang. The other forms of this genus all became extinct.

The hominid line never modified in a brachiating direction and never developed the powerful canine teeth found in all pongids including Proconsul. We know that at the same time as Proconsul there existed at least two distinctive hominids which are almost certainly either the immediate ancestors of Australopithecus (the precursor of man) or was actually the first known Australopithecus. These hominids are known as Ramapithecus and Kenyapithecus, the latter discovered by Leaky in 1962. Ramapithecus has been found in India, Africa and Europe.

It has been suggested that there may be a connection between this hominid line and a very unspecialized little monkey-like type, Propliopithecus, which lived in Egypt 34 million years ago and had the pattern of teeth and jaw characteristic of the later hominids. At roughly the same time there was, also in Egypt, another type with well marked canines, Aegyptopithecus, which may indicate the ancestral type of the Pongidae.