CHAPTER IX 



THE HUMAN FACTOR IN PLANT EVO- 

 LUTION 



THE changes in the vegetation of the earth due 

 to the direct or indirect agency of man have 

 been great and far-reaching. Like all other animals, 

 the very existence of man is dependent upon plants 

 of some kind, and most races of mankind rely upon 

 some single species of plant as the staff of life. 

 While the Eskimos of the frozen North, and the 

 nomad tribes of Indians of the western plains, de- 

 pend mainly upon the products of hunting and fish- 

 ing for their existence, by far the larger part of 

 mankind are vegetarians in their diet, animal food 

 playing a quite secondary role. If the original home 

 of man was in the eastern tropics, as there seems 

 every reason to believe was the case, his natural 

 food would probably have been mainly fruits, seeds, 

 and roots. Such shelter as was necessary for him 

 was furnished by bunches of branches or leaves, or 

 mud huts thatched with grass or palm-leaves, such 

 as we now find among many of the lower savage 

 tribes. Even at the present day, wild plants yield 

 a not unimportant source of food for mankind. 

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