226 INTRODUCTION TO EVOLUTION 



Passing on to the Miocene and Pliocene we note the Dryopithecinae, 

 ancestral to orang-utan, chimpanzee, and gorilla. Were they also ancestral 

 to man? This question has been answered both "yes" and "no." The dia- 

 gram indicates the possibility that they may have been but also indicates, 

 by the open channel to the left of the name "Dryopithecinae," that other, 

 still-unknown Miocene forms may have been ancestral, either to the ex- 

 clusion of the Dryopithecinae or in addition to them. 



The question of the ancestral position of the Dryopithecinae is of interest 

 since it involves the whole question of man's relationship to the apes. 

 Among living primates the chimpanzee and gorilla are man's closest rela- 

 tives, as judged by many similarities of structure of both skeleton and "soft 

 parts," and including such things as the type of placenta and the results of 

 serological tests (see pp. 111-113). But there are also differences. Some of 



\a^I 



son 



FIG. 11.3. Gorilla. (Drawn by Maurice Wilson; from Le 

 Gros Clark, Hisfory of the Primates, British Museum [Natu- 

 ral History], 1949, p. 34.) 



the most striking of the differences are connected with the manner in 

 which apes travel through the trees. Modern apes are strongly specialized 

 for arm-swinging, for brachiation. True, the massive gorillas no longer 

 spend much time in the trees, but their anatomy bears incontestable evi- 

 dence that their immediate forebears were brachiators. Among the special- 



