354 



THE RISE OF ANIMAL LIFE 



Fig. 13-73. The gorilla {Gorilla gorilla) is the largest and 

 probably the most intelligent of all the great apes. 

 This is a young male that has just been enticed into 

 new quarters which it Is thoroughly investigating. 



the ground, retreating to the trees only to 

 sleep. Man, of course, is the only one that 

 has succeeded in making the complete 

 transition from arboreal to ground life. 



The chimpanzee possesses a disposition 

 more favorable to captivity and for that 

 reason a great deal more is known about its 

 behavior than that of any of the other 

 great apes. In size it matches man very 

 well, being about 5 feet in height and 

 weighing about 150 pounds when full 

 grown. When young it is easily handled, 

 and is a very affectionate, playful, and 

 extremely curious animal. It seems to ap- 

 proach the human type of intelligence as 

 illustrated by its ability to solve problems. 

 Experiments, notably those by Yerkes, have 

 shown that the "chimp" will solve simple 

 problems much like a small child. For ex- 

 ample, if food is placed just out of its reach 

 and several boxes are placed near by, the 



chimp will pile the boxes in order to obtain 

 the food. It has also been found that, if 

 given two bamboo poles which fit together, 

 it will so place the two parts in order to 

 reach a desired object. This requires a kind 

 of intelligence far greater than that pos- 

 sessed by the smartest carnivores. 



The gorilla is perhaps more intelligent 

 than the chimpanzee, but because of its 

 sullen and individualistic disposition it will 

 not tolerate training or testing of any sort 

 (Fig. 13-73). A two-year-old gorilla re- 

 sponds very similarly to a child of about 

 the same age or a little older. Soon, how- 

 ever, it develops a morose disposition and 

 cannot be trusted for close association with 

 man. In size the gorilla exceeds all other 

 primates, and an old male may reach a 

 height of 6 feet and a weight of 500-600 

 pounds. Its massive torso and long, very 

 powerful arms make it a formidable beast 

 in a battle with almost any other animal. 

 Because of its herbivorous diet the gorilla 

 is not a predator, and for that reason does 

 not get into much trouble. Since it is shy, it 

 retreats into the dense forest and will not 

 fight unless provoked. The gorilla walks 

 rather well on the ground but frequently 

 reverts to all fours, especially when in a 

 hurry. Its short sturdy legs and man-like 

 feet support its weight well, although it is 

 not a swift runner. 



The next step— man 



The great apes apparently had a greater 

 day during the Miocene and Pliocene than 

 they have had since. They lived over vast 

 areas of Africa, China, and even large parts 

 of Europe. One of these, Dryopithecus, 

 ranged over all of these regions and, it is 

 thought, may have been the stem from 

 which the present-day great apes and man 

 were derived. It seems that this animal was 

 well adapted to tree life, being able to 

 brachiate expertly, although its arms did 

 not reach the length of those of the gibbon. 

 It may be that these fomis descended to 

 the ground in the upright position they had 



