THE PROGRESSION OF LIFE ON EARTH 



apes, they must be regarded as the ancestors of both the 

 modern apes and man. Not all the stages between the ape 

 and man have yet been found, because the higher the brain 

 power the more wary the animals would become in avoiding 

 accidents by which their remains could be buried in the earth ; 

 but the few fragments that are known show that the links 

 certainly existed. The teeth and jaws of fossil apes suggest 

 that they belonged to animals which may have been ancestral 

 to man as well as to modern apes, and the oldest known 

 fossil human skulls and jaws exhibit more ape characters 

 than any human skull and jaw of the present day. 



The oldest jaws of apes thus far discovered are from the 

 early Tertiary (Oligocene) deposits of Egypt and belong to 

 animals smaller even than the existing gibbons, the smallest 

 living apes. They have a short, bony chin and small canine 

 teeth. By a very slight reduction of the canine teeth and 

 equally slight changes in the molar teeth the heads of these 

 apes would approach in form the modern human head. By 

 an enlargement of the canine teeth and a lengthening of the 

 bony chin they would acquire the jaw of an existing ape. 



The jaws of the next higher apes, from the middle Tertiary 

 (Upper Miocene and Lower Pliocene) of Europe, represent 

 larger animals, equalling in size a modern chimpanzee. The 

 so-called "forest-ape" {Dryopithecus^ now has powerful 

 canine teeth, and so is approaching the modern apes rather 

 than man; but its molar teeth are remarkably human in 

 appearance, and the short, bony chin was less prominent 

 than that of the chimpanzee and gorilla. 



Teeth and fragments of jaws of several other apes from 

 rocks of the same age in India show that in this region there 

 must have been more variety among apes than is seen any- 

 where at the present day. There is, in fact, good reason for 

 supposing that these animals may have included some of the 



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