742 



GENETICS AND EVOLUTION 



Figure 36.5. 'Hie wliite-banded gibbon. Ihcse anthropoid apes use their long 

 arras to swing from tree to tree with great agiHty. (Courtesy of the San Diego Zoo.) 



to the ground when it stands erect (Fig. 36.5). Its slender, graceiul body 

 is covered with iur. Gibbons are the most skiUiul "brachiators," swing- 

 ing gracetully and surely Irom branch to branch, clearing 20 to 40 ieet 

 at each swing and using the arms alternately. The spectacular aerial 

 acrobatics of the gibbon requires great agility, coordination, keen eye- 

 sight, and the ability to make rapid judgments of distance and possible 

 landing sites. 



The orang-utan, a native of Borneo and Sumatra, is a bulky and 

 powerful animal covered with long, reddish-brown hair. Although it is 

 short-legged and scarcely five feet tall, it may weigh as much as 160 

 pounds. Orang-utans have enormously long arms, with a span of 7 or 

 8 feet, and long, slender hands and feet. They are successful arboreal 

 animals, but because of their considerable weight they move more de- 

 liberately than the gibbons do. Orangs eat fruit and leaves and build 

 nests in trees on which to sleep. 



Chimpanzees and gorillas both live in Africa, are closely related, 

 and have many characteristics in common. Both are more terrestrial and 

 less arboreal than the other apes, and have relatively shorter arms and 

 longer, stronger legs than gibbons and orangs. Both are large, powerful 

 animals; a male chimpanzee is about 5 feet tall and weighs 150 pounds 

 and a male gorilla may be over 6 feet tall and weigh as much as 500 

 pounds. Chimpanzees are primarily tree-dwellers but are quite at home 

 on the ground and walk in a semierect position. The hands and feet of 

 the chimpanzee are long and narrow, with small thumbs and great toes, 

 but those of the gorilla are shorter and broader, more closely resembling 



