224 ANIMALS OF THE PAST 



that in some portions of their range they may 

 have been extirpated by a change in food-sup- 

 ply, due in turn to a change in climate, it seems 

 preposterous to claim that there was not at all 

 times, somewhere in this vast expanse of terri- 

 tory, a climate mild enough and a food-supply 

 large enough for the support of even these 

 huge, sluggish creatures. We may evoke the 

 aid of primitive man to account for the disap- 

 pearance of this race of giants, and we know 

 that the two were coeval in Patagonia, where 

 the sloths seem to have played the role of do- 

 mesticated animals, but again it seems incred- 

 ible that early man, with his flint-tipped spears 

 and arrows, should have been able to slay even 

 such slow beasts as these to the very last indi- 

 vidual. 



Of course, in modern times man has directly 

 exterminated many animals, while by the in- 

 troduction of dogs, cats, pigs, and goats he has 

 indirectly not only thinned the ranks of ani- 

 mals, but destroyed plant life on an enormous 

 scale. But in the past man's capabilities for 

 harm were infinitely less than now, while of 

 course the greatest changes took place before 



