PHYLOGENY 



Proconsul. Anthropoid remains from the Miocene are very numerous, 

 especially in east Africa, where a variety of fossil apes has been found. 

 Some of these, belonging to the genus Proconsul, range in size from rather 

 small animals up to some approaching the size of a gorilla. The limb bones 

 indicate that these Miocene apes were of much lighter build than modern 

 apes. Specializations for brachiation are either lacking, or very moderate. 

 The teeth of Proconsul show some moderate specializations in the direc- 

 tion of the great apes. The skull, however, is more generalized, and re- 

 sembles those of the smaller Old World monkeys. Moreover the brain, 

 as shown by endocranial casts, resembled those of monkeys rather than 

 anthropoid apes. An animal similar to Proconsul, but lacking its dental 

 specializations, could have been ancestral to both the Hominidae and the 

 Pongidae. 



Dryopithecines. While the early Miocene development of the apes 

 appears to have occurred in central Africa, they soon spread. In the late 

 Miocene and early Pliocene, apes are known from several localities in 

 Europe and India. The several genera are collectively called the sub- 

 family Dryopithecinae, but it is doubtful that this heterogeneous array is 

 a natural taxonomic group. One of the Pliocene genera, Dryopithecus, 

 was very widespread, very common, and represented by many species. 

 This was a fairly large ape, comparable to the chimpanzee of today. Vari- 

 ations of the teeth in different species suggest in some cases the chimpan- 

 zee, in others the orangutan, and in still others, the gorilla. It has been 

 suggested that Dryopithecines may be ancestral to all of these modern 

 types. (The gibbon and siamang appear to have been derived from an- 

 other Pliocene genus, PUopithccus. ) Only two limb bones of Dryopithecus 

 have been recovered, one humerus and one femur. They indicate that 

 Dryopithecus was more slender than its modern descendants, and that it 

 was not yet specialized for brachiation. 



It has been much debated whether man could have been derived from 

 a dryopithecine. On the positive side, the limb structure of these apes, 

 as far as it is known, was still primitive, and could conceivably have given 

 rise either to the limbs of man or to those of the apes. But the teeth show 

 specializations of a type not found in man, including enlarged, pointed, 

 tusk-like canines. Those who oppose the dryopithecine ancestry of man 

 suggest that the ancestors of man must have branched off before the den- 

 tal specializations had developed. Much more evidence is needed, espe- 

 cially with regard to parts of the skeleton other than the skull and teeth. 

 Straus believes that the line of descent leading to man probably branched 

 oft from the primitive catarrhine stock when the latter was more monkey- 

 like than ape-like, and hence before the development of actual anthropoid 

 apes. 



Oreopithecus. More promising as a Pliocene ancestor of man is Oreo- 

 pithecus, a primate from the early Pliocene of Tuscany, which was de- 

 scribed in 1872 as a fossil monkey, and then largely forgotten. Re-exami- 

 nation by Hiirzeler has revealed many hominid characters, and other 

 students have concurred in his judgment. Materials studied include many 

 fragments of skulls, jaws ( Figure 65), and teeth, as well as some vertebrae 



184 



