12 GENEEAL EVOLUTIOif. 



of hind foot not opposable. In monkeys we have the reverse of 

 all these characters. But what do we see in young monkeys ? A 

 head and brain as large relatively to the body as in man ; a facial 

 angle quite as large as in many men, with jaws not more promi- 

 nent than in some races ; the arms not longer than in the long-armed 

 races of men, that is, a little beyond half way along the femur. 

 These observations are made on a half-grown Cetus apella, from 

 Brazil, a member of a group more remote from men than are the 

 Old World apes, yet with an unusually large facial angle. At 

 this age of the individual the distinctive characters are therefore 

 those of homo, with the exception of the opposable thumb of the 

 hind foot, and the longer canine tooth ; nevertheless, the canine 

 tooth is shorter in the young than in the adult. 



Now, in the light of various cases observed, where members of 

 the same sj^ecies or brood are found at adult age to differ in the 

 number of immature characters they possess, we may conclude 

 that man originated in the following way : that is, by a delay or 

 retardation in growth of the body and fore limbs as compared with 

 the head ; retardation of the jaws as compared with the brain 

 case, and retardation in the protrusion of the canine teeth. The 

 precise process as regards the hinder thumb remains obscure, but 

 it is probably a very simple matter. The projDortions of the 

 young Cehus apella enable it to walk on the hind limbs with great 

 facility, and it does so much more frequently than an adult G. 

 capiicinus with which it is confined.* 



The *' retardation" in the growth of the jaws still progresses. 

 Some of our dentists have observed that the last (3d) molar teeth 

 (wisdom teeth) are in natives of the United States very liable to 

 imperfect growth or suppression, and to a degree entirely unknown 

 among savage or even many civilized races. The same suppres- 

 sion has been observed in the outer pair of superior incisors. 

 This is not only owing to a reduction in the size of the arches of 

 the jaws, but to successively prolonged delay in the appearance of 

 the teeth. In the same way men, and the man-like apes, have 

 fewer teeth than the lower monkeys, and these again fewer than 

 the ordinary Mammalia, and this reduction has proceeded in rela- 

 tion to an enlargement of the upper part of the head and of the 

 brain. 



The cause of development may be next considered, and under 



* The same relations of man to the anthropoid apes have been dwelt upon by 

 Prof. C. Yogt. 



