734 MAMMALIA. 



Family 5. Hominid^e. Genus Homo. 



The distinctiveness of man from his nearest allies depends 

 on his power of building up ideas and of guiding his 

 conduct by ideals. But there are some structural peculiarities 

 of interest. 



Man alone, after his infancy is past, walks thoroughly 

 erect. Though his head is weighted by a heavy brain, 

 it does not droop forwards. With his upright attitude, the 

 increased command of vocal mechanism is perhaps in part 

 connected. 



Man plants the soles of his feet flat on the ground ; the 

 great toes are often longer, never shorter than the others, 

 and lie in a line with them ; he has a better heel than 

 monkeys have. No emphasis can be laid on the old dis- 

 tinction which separated " two-handed " men (Bimana) from 

 the " four-handed " monkeys (Quadrumana), nor on the fact 

 that men are peculiarly naked. But " the arms are shorter 

 than the legs, and, after birth, the latter grow faster than the 

 rest of the body." 



Compared with the anthropoid apes, man has a bigger 

 forehead, a less protrusive face, smaller cheek-bones and 

 supra-orbital ridges, a true chin, and more uniform teeth 

 (2, 1, 2, 3), forming an uninterrupted horseshoe-shaped 

 series without conspicuous canines. 



More important, however, is the fact that the weight of 

 the gorilla's brain bears to that of the smallest brain of 

 an adult man the ratio of 2 : 3, and to the largest human 

 brain the ratio of 1 : 3 ; in other words, a man may have 

 a brain three times as heavy as that of a gorilla. The brain 

 of a healthy human adult never weighs less than 31 or 32 

 oz. ; the average human brain weighs 48 or 49 oz. ; 

 the heavest gorilla brain does not exceed 20 oz. "The 

 cranial capacity is never less than 55 cubic in. in any 

 normal human subject, while in the Orang and Chimpanzee 

 it is but 26 and 27^ cubic in. respectively." 



But, as Owen allowed long since, there is an " all-pervad- 

 ing similitude of structure " between man and the anthro- 

 poid apes. As far as structure is concerned, there is much 

 less difference between man and the gorilla than there is 

 between the gorilla and the marmoset. 



