280 Plant Life and Evolution 



fruits or grains which were sufficiently superior to 

 the common wild forms to attract the attention of 

 the primitive husbandman, who would naturally pre- 

 fer these, and at the same time may have taken 

 the trouble to plant the seeds of these superior 

 forms, thus inaugurating a most important epoch 

 in the history of mankind, since the development of 

 agriculture made it possible for man to spread to 

 regions which without cultivation would have been 

 unable to support him. 



Succeeding the more or less casual planting about 

 his dwelling of wild fruit-trees, it may be surmised 

 that primitive man began to follow methods of agri- 

 culture approximating some of those in vogue 

 among savage races at the present day, and indeed 

 not entirely unknown to the white man. The native 

 of the tropics and of the Southern Alleghanies 

 still girdles the trees so as to make a clearing in the 

 forest, and plants his crops in the space thus opened 

 to the sunlight. After a few crops have been taken 

 off from this clearing, it is deserted and another 

 one made. Nature promptly repairs the damage, 

 and another generation sees the forest again in pos- 

 session. 



The extension of agriculture to more arid re- 

 gions necessitated more careful methods, and it was 

 especially in such regions that the most scientific 

 methods of agriculture, including irrigation, had 

 their birth, and thus were made possible the civiliza- 

 tions of Babylonia and Egypt, Mexico and Peru. 



