ADAPTATION TO ENVIRONMENT 39 



particular environment, has touched the limit of both 

 its necessity and its power to "advance." There exists 

 abundant and reliable evidence of the fact that wherever 

 man has been subjected to the stunting influences of 

 an unchanging environment fairly favorable to life, he 

 has shown no more disposition to progress than the most 

 stolid animals. Indeed, he has usually retrograded. 

 The need to fight for food and home has been the 

 spur that has ever driven man forward to establish the 

 manifold forms of physical and mental life which make 

 up human existence to-day. Like the simple adaptive 

 mechanisms of the plant, by which it gets air, and of 

 the animal, by which it overcomes its rivals in battle, 

 the supremely differentiated functions of thought and 

 human relations are the outcome of the necessity of 

 the organism to become adapted to entities in its en- 

 vironment, and are best explained by a study of the 

 details of this relationship. 



