484 



THE CHANGING GENERATIONS 



29.14C and 29.15B). Careful study has shown that the members of this 

 genus show divergent evolutionary trends. Some represent lines that 

 have since disappeared; some suggest the chimpanzees and gorillas; in 



Fig. 29.15. Human and near-human dental arches, showing the widening of the arch, short- 

 ening of the tooth row, and reduction in size of canines and molars from ape to man. A, 

 gorilla. B, Dryopithecus. C, South African Sterkfontein man-ape, Plesianthropus. D, 

 modern man. (Redrawn from Howells, Mankind So Far, by permission Doubleday & Com- 

 pany, Inc.) 



others it is possible to see faint suggestions of human characteristics. 

 All were certainly apes and not primitive men, for the canines are strong 

 tusks and the tooth arch is U-shaped. It is highly probable that among 



these Miocene apes are to be sought 

 the beginnings of two divergent 

 evolutionary lines, one leading to 

 the chimpanzees and gorillas and 

 the other to man. 



This hypothesis is given support 

 by an interesting discovery made by 

 Leakey in Africa. As a climax to 17 

 years of search for fossil anthropoids, 

 in 1948, he found on an island in 

 Lake Victoria Nyanza the nearly 

 complete skull of a Miocene ape, 

 which he has since christened Pro- 

 consul. It seems to belong near the 

 base of the human stock, for while it 

 was a small, primitive, chimpanzee- 

 like creature, it lacks brow ridges and 

 shows certain other prehuman fea- 

 tures in teeth and skull which put it a step beyond Dryopithecus in the 

 direction of man. 



The man-apes of South Africa. Little is known of primate evolution 

 during the Pliocene, when the human stock was taking shape. In South 

 Africa, however, Broom and Dart have discovered a number of fossil 



Fig. 29.16. The skull of the South African 

 Kromdraai man-ape Paranthropus, re- 

 stored. (Redrawn from Howells, Mankind 

 So Far, by permission Doubleday & Com- 

 pany, Inc.) 



