No. 536] ADAPTATIONS OF THE PRIMATES 489 



was another group of primates which, tended to come to 

 the ground, and these tended to assume a more or less 

 upright position, with a bipedal gait. The hands thus 

 free to take hold of objects, were free to develop a deft- 

 ness and adaptability, which seems to be the key to the 

 progressive development of the apes. It seems however 

 that this handling of objects (food, sticks, stones) began 

 before they left the trees and was really the cause of 

 taking the bipedal gait. The climbing offered an ever 

 changing grasp and carrying food to the mouth wasanat- 

 ural starting point; so that, with the front paws used as 

 hands, there is a good reason for exempting them from 

 the heavy work of locomotion. Contributory to this idea 

 is the eolith development. These crude flaked flints 8 

 begin back in the Miocene at least, and as Penck 9 sug- 

 gests the only known primate which might be suggested 

 as an eolith-maker is Dryopithecus. It seems highly 

 probable then that the hands had begun to be used as such 

 before the first apes came to the ground and that this 

 specialization of the hand was the cause of the upright 

 position and bipedal gait. Of course the varied exper- 

 ience resulting from taking up all sorts of objects and 

 using them for different purposes tended to develop the 

 intelligence, and that furthered handling, the two acting 

 and reacting on each other. 



In the early Pliocene of southern Europe three divi- 

 sions of the simian group have already arisen, 10 one 

 group remaining arboreal, or more probably reverting 

 again to the trees, a second group developing great mus- 

 cular and skeletal strength, the third group developing 

 especially the brain and central nervous system. 



The first of these groups, i. e., the retrogressive or 

 aboreal group, is represented in the Upper Miocene of 

 southern Europe by Pliopithecus, a form ancestral to the 

 modern gibbons, and one which during the upper Miocene 



'See MacCurdy, Amer. Anthrop., Vol. 7, n. s., pp. 42o_479, 1905. 



9 Science, Vol. 29, n. s., p. 359, 1909. 



10 See Schlosser, Zoologischoi Anzeiger, Vol. 22, p. 289, 1900. 



