POPULAR SCIENCE 89 



those of the baboon, macaque, or gibbon, but they are very 

 formidable weapons. They seem to have been developed as im- 

 plements for obtaining food. The gorilla eats the kernel of nuts 

 with very hard shells, and gnaws great pieces out of the trunks 

 of trees in order to get access to the pith. " Here is probably 

 one purpose of that enormous strength of jaw which long 

 seemed to me to be thrown away on a non-carnivorous animal. 

 These habits account for the great canines becoming worn, as 

 they are in almost all adult gorillas." Hence the great bony 

 ridges on the skull, the early closing of the sutures, and the 

 large spinous processes of the vertebrae of the neck. In order 

 to wrench off the pieces of wood the immense muscles have 

 been developed and lead to " the almost total absence of the 

 neck which gives the head the appearance of being set into 

 the shoulders." ^ The older the fossil of the ape the smaller 

 are the teeth and bony ridges in proportion to the size of the 

 animal, Propliopithecus having small teeth of uniform height 

 approaching in appearance the human series. Moreover, the 

 permanent canines of the great apes are guided into their 

 position by the milk canines, whereas the human canines do 

 not appear until the eleventh or twelfth year. In the meantime 

 our permanent incisors and bicuspids have long been in position, 

 and the canine is often crowded out of its proper place and 

 forced to fall out of line. " Back teeth " are therefore not 

 evidence of our simian ancestry, but on the contrary quite the 

 opposite. 



The junction of the premaxillary bone and the maxilla has 

 been the favourite site for the appearance of great teeth ever 

 since the theriodont reptiles lived in the Permian period. The 

 growing and ossifying tissues along the edges of the two bones 

 are the parts most richly supplied with blood. This fact, in 

 conjunction with the intermittent pressure caused by biting, 

 appears to be the explanation of the commanding size of the 

 teeth which grow next the suture. These are the canines in 

 most cases, but the lateral incisor forms the tusks of the elephant, 

 mammoth, and rhinoceros. With the exception of man, all the 

 primates have specialised in the canines, and the greatest of 

 all is the gorilla. 



These considerations enable us to offer a probable solution 

 of the history of the premaxilla. In the early primate, when 

 he first came from the trees, it was a small bone, perhaps less 

 than half an inch across. The structure which was of service 

 to the gibbon, orang, and gorilla was not this bone, but the 

 suture with its special blood-supply, which separated it from the 

 maxilla. Those apes survived which had the largest canine 

 teeth, and the line of the suture was essential to the increase 

 ^ Du Chaillu, Equatorial Africa, 1890, pp. 272 et seq. 



