THE EVOLUTION Of MAN 743 



those of man. The gorilla has a massive head, with large bony crests on 

 top of the skull for the attachment of the neck and jaw muscles and 

 with prominent bony ridges over the eyes. The gorilla walks, like man, 

 on the soles of his feet with the toes extended, rather than on the outer 

 edge of the foot with the toes curled underneath as do other apes. Both 

 chimpanzees and gorillas may build nests in low trees. 



Psychologic studies of chimpanzees and gorillas have shown that 

 they are curious, perceptive, able to reason, and have strong emotions 

 and social instincts. 



Man is more nearly similar to the chimpanzee and gorilla than to 

 any other primate, yet differs in enough characters to be placed in a 

 separate family, the Hominidae. The anatomic differences between the 

 great apes and ourselves are rather small, and are generally differences 

 in proportion of parts correlated with our adaptation to terrestrial life. 

 Some of the characters which distinguish man from the other primates 

 are: (1) man's posture is fully erect; (2) his legs are longer than his arms; 

 (3) his great toe is not opposable, but is in line with the others and 

 adapted for walking; (4) the human foot is adapted for bearing weight 

 by the presence of lengthwise and transverse arches; (5) man's brain is 

 large— two to three times larger than the gorilla's; (6) the human nose 

 has a prominent bridge and a peculiar, elongated tip; (7) the upper lip 

 has a median furrow, and both lips are rolled outward so that the mu- 

 cous membrane is visible; (8) man has a jutting chin; (9) his canine teeth 

 project slightly, if at all, beyond the level of the others, and (10) man 

 is relatively hairless. 



There is no single ape that resembles man in all respects more than 

 the other apes. The hands, feet and pelvis of the gorilla most closely 

 resemble man's, but the skull and hair color of the chimpanzee are 

 nearest to the human. The orang is the only ape to have the same num- 

 ber of ribs we have, and the posture and gait of the gibbon is most 

 nearly human. With respect to any structure or proportion of parts, 

 however, the difference between man and any of the great apes is less 

 than between any of these and the monkeys. 



322. The Man Apes 



From Pleistocene cave deposits in South Africa have come the re- 

 mains of fossil anthropoids that almost bridge the gap from ape to man. 

 These man apes probably existed too recently to be man's ancestors, but 

 they show the kind of changes by which the transition from ape to man 

 was made. They are no^v regarded as "progressive apes," adapted tor 

 walking upright on the ground, which evolved independently of the 

 human line from common dryopithecine ancestors m the Miocene. 



The first of these fossils, the skull of a baby man ape, was found 

 in the Transvaal by Dart in 1925 and named Australopithecus (Fig 

 36.6). Subsequentlv, Dart and Broom found adult skulls and parts of 

 skeletons, and although these were given separate names, Plesianthropus 

 and Paranthropus, they probably represent animals very closely related 

 to, if not identical with, the original Australopithecus These australo- 

 pithecines have an interesting mixture of apelike and human character- 

 istics The head was apelike, with a low-vaulted skull, protruding muzzle 



