XIII 



WHY DO ANIMALS BECOME EXTINCT? 



"And Sultan after Sultan with his Pomp 

 Abode his destined Hour and went his way." 



It is often asked "why do animals become extinct?" 

 but the question is one to which it is impossible to give 

 a comprehensive and satisfactory reply; this chapter 

 does not pretend to do so, merely to present a few 

 aspects of this complicated, many-sided problem. 



In very many cases it may be said that actual ex- 

 termination has not taken place, but that in the course 

 of evolution one species has passed into another; 

 species may have been lost, but the race, or phylum 

 endures, just as in the growth of a tree, the twigs and 

 branches of the sapling disappear, while the tree, as a 

 whole, grows onward and upward. This is what we see 

 in the horse, which is the living representative of an 

 unbroken line reaching back to the little Eocene Eohip- 

 pus. So in a general way it may be said that much of 

 what at the first glance we might term extinction is 

 really the replacement of one set of animals by another 

 better adapted to surrounding conditions. 



Again, there are many cases of animals, and particu- 

 larly of large animals, so peculiar in their make up, so 

 very obviously adapted to their own special surround- 

 ings that it requires little imagination to see that it 

 would have been a difficult matter for them to have re- 

 sponded to even a slight change in the world about 

 them. Such great and necessarily sluggish brutes as 

 Brontosaurus and Diplodocus, with their tons of flesh, 

 small heads, and feeble teeth, were obviously reared in 

 easy circumstances, and unfitted to succeed in any 

 strenuous struggle for existence. Stegosaurus, with 

 his bizarre array of plates and spines, and huge-headed 



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