XV 



THE INFLUENCE OF THE ENVIRONMENT 



UPON MAN 



1. The way has now been cleared for a consideration of the 

 influence of the environment upon man. The relation of the 

 ancestors of man to the environment must have been the same 

 as that between any wild species and its environment. In the 

 course of his history man has moved away from this position 

 until his relation to the environment has become so different 

 from that described for other animals and plants that we can no 

 longer speak of a normal environment. This has not come about 

 because man is not subject to the same laws as are other organisms. 

 It has come about because his relation to the environment has 

 been modified in many ways. 



The conception of the normal environment involved the idea 

 that, much as the different elements composing the environment 

 might vary, there was some more or less clearly defined limit to 

 their variations. In one sense this remains true for man ; but 

 the variations are so much greater in degree and in kind that 

 there is a clear distinction between the conditions obtaining 

 among civilized races and those obtaining among any wild species. 

 Let us glance for a moment at what has happened. It is obvious 

 that man has varied his surroundings in every respect, not only 

 with regard to what we may call external circumstances, but also 

 with regard to nutrition and to customs and habits that we sum 

 up under the name of use. The most obvious changes in external 

 circumstances are those connected with the spread of man to 

 every corner of every continent. Man has become subject to 

 every extreme of heat and cold, humidity and aridity, of barometric 

 pressure and all that goes to make up climate. There is in 

 addition a vast mass of artificial influences, due in the first place 

 to various methods of protection adopted against climate. Every 

 description of house is known, involving all degrees of access to 

 fresh air. Dress again varies almost infinitely — the variations all 

 being of possible influence upon the development of mental and 



