THE HUMAN BACKGROUND 



429 



that no living species represents the direct human ancestor. The 

 chimpanzee-gorilla group is regarded as the nearest to Man, but 

 these apes have evolved along different lines since the divergence of 

 the human lineage in the geologic past. Apparently the common 

 ancestor was a rather large animal with a mode of life more similar 

 to the present-day Gibbons than to either the Chimpanzees or the 

 Gorillas, although anatomically the Gibbons to-day differ more 



Fig. 274. — Gorilla, Gorilla gorilla. Note large head, small ears, short 

 lips, large canine teeth, ridges above eyes, and absence of a chin. The gorilla 

 walks on the backs of its fingers. Height about 5^ feet, weight 500 pounds. 

 (From Hegner, drawn by R. Bruce Horsfall.) 



markedly from Man than do any of the other anthropoid apes. 

 Gibbons are relatively small active animals with such very long 

 arms that the knuckles reach the ground even when the body is 

 erect. But they are strictly arboreal forms whose amazing adapta- 

 tions for progression through the foliage of trees has been suggested 

 as of prime importance in the development of their mentality ; and 

 so possibly it was with the prehuman ancestors. (Figs. 93, 273, 274.) 

 Receding still further into the past, there were antecedent to the 

 common ancestor of the anthropoid apes and Man more and more 



