THE HAZARDS OF THE PAST 



as changed geographical conditions, changes of cli- 

 mate, affecting the food- supply, extreme speciaHz- 

 ation, like that of the sabre-toothed tiger whose 

 petrified remains have been found in various parts 

 of this continent, and who apparently was finally 

 handicapped by his huge dental sabre. Probal)ly 

 many more species of animals have become extinct 

 than have survived, but none of these could have 

 been in the fine of man's descent, else the human 

 race would not have been here. If the Eocene pro- 

 genitor of the horse, the little four-toed eohipi>us, 

 had been cut off, would not the world have been 

 horseless to-day? The horse in America became ex- 

 tinct, from some cause only conjectural, many tens 

 of thousands of years ago. Had the same fate be- 

 fallen the horse in Europe and Asia, it seems prob- 

 able that our civilization would have been far less 

 advanced to-day than it is. 



The fate of every species of mammal in our time 

 seems to have been in the keeping of a single form 

 in early Tertiary times. The end of the Cretaceous 

 or chalk period saw the extinction of the giant rep- 

 tiles both of sea and of land, at the same time that 

 it saw the appearance of a great many species of 

 small and inconspicuous mammals, among which 

 doubtless were our own humble forebears. Extreme 

 specialization in any direction may narrow an an- 

 imal's chances of survival; they have but one chance 

 in the game of life, whereas an animal with a more 



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