570 HUMAN BIOLOGY 



ages may be a part of his environment. Furthermore, by 

 intelHgence and social cooperation, men are able to control 

 their environment as no other creatures can. Indeed it may 

 be granted at once that the only possibiHty of the purposive 

 improvement of the race hes in the control of environment, 

 using this term in its broadest sense, and thus including the 

 selective agency in propagating good stock and ehminating 

 bad. For even the improvement of heredity must rest upon 

 science, education and social cooperation and all of these are 

 parts of human environment. 



The great importance of environment in human hfe and 

 progress has led some environmentahsts to minimize the 

 importance of heredity. They sometimes assert that it 

 determines only unimportant physical traits such as the 

 color of the eyes or hair, and that environment determines 

 all the rest. But of course there is a basis in the germ cells 

 for everything that will ever develop out of those cells 

 and in many instances this germinal basis is the differential 

 cause of many important characters. It is needless to 

 say this to biologists, but there are some psychologists, 

 sociologists and apostles of human equality who still main- 

 tain, in the realm of theory but not in actual practice, 

 that "all men are born equal" and that the differences be- 

 tween races and classes and individuals are caused only by 

 differences in environment, and not by differences in heredity. 



Of course the major differences that distinguish one 

 species from another are inherited; each "produces seed after 

 his kind." Men differ from horses or dogs primarily 

 because they come from different kinds of germ cells. In the 

 same incubator and under practically identical conditions, 

 a hen's egg develops into a chick, a duck's egg into a duckling. 

 Similarly racial traits, such as those that characterize 

 different breeds of dogs or horses or men, are inherited. This 

 is true not only of physical but also of psychical character- 

 istics; the bull dog, or pointer, or hound inherits not only his 

 physical but also his mental and temperamental traits; 

 the European, the Asian, or the African inherits not only 

 his skin color, hair form, shape of eyes, nose, lips. Jaws and 

 skull, but also many of his mental, emotional and social 

 peculiarities. 



