224 



INTRODUCTION TO EVOLUTION 



Old li 

 World III 

 Monkeys '; 



Homo sapiens 



Cro-Magnon 



Oreopithecus 



Parapithecus 



Lemurs and 

 Tarsiers 



Tree shrews 



Proconsul 

 Dryopithecines 



FIG. 1 1.2. The evolution of primates during the Cenozoic era. 



belonged to a creature which some writers call a monkey and others 

 an ape. Since the jaw and teeth are quite unspecialized, along lines of 

 specialization followed by either later monkeys or later apes, we may be 

 wise not to try to classify the creature as either the one or the other. 

 From our standpoint Parapithecus is most interesting as evidence that 

 there existed in Oligocene times primates so primitive in structure that they 

 could have been the ancestors both of later Old World monkeys and of 

 apes (Gregory, 1951; Colbert, 1955). 



The Old World monkey "channel" of the diagram is shown separating 

 from the rest of the "river" during the Oligocene. The same is true among 

 the apes for the "channel" leading to the gibbon (Fig. 11.2). Not only is 

 Parapithecus a probable ancestor of the gibbon, but two other fossils, 

 Propliopithecus from the Oligocene and Pliopithecus from the Miocene, 

 indicate something of the subsequent course of gibbon evolution. Modern 

 gibbons, at home in southeastern Asia and the East Indies, are slender- 



