Animals Before Man 



large land animals of North America; while 

 South America, the former headquarters of the 

 giant sloths and home of whole families of huge 

 mammals, is now quite devoid of large mam- 

 mals, unless we are willing to bestow that term 

 U23on tapirs. Of all the continents, Africa alone 

 presents anything like the conditions that were 

 once common. On the other hand this is the 

 age of great cetaceans, and there is no evidence 

 that at any time were there any aquatic ani- 

 mals, or, for that matter, any animals, so large 

 as existing whales. 



In view of the large numbers of predatory 

 animals that flourished in the past the reader 

 may naturally have wondered why these crea- 

 tures did not eat one another out of existence. 

 But the destruction of animals by one another 

 is not exterminative and corrects itself. If 

 beasts of prey should increase unduly and food 

 become scarce, there would soon be a balance 

 struck by starvation. Any increase among 

 creatures that are not predatory — insects for ex- 

 ample — is followed by an increase of their ene- 

 mies, and again the balance is struck. It is 



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