270 Heredity and Environment 



lution since it assumes that the earliest organisms were geneti- 

 cally the most complex. 



But if, as is often said, evolution from amoeba to man neces- 

 sarily involves the addition of many new inheritance factors it 

 does not involve additions from without as Bateson implies. New 

 hereditary factors are to be thought of as we think of new chemical 

 compounds, which are formed by new combinations of the same 

 old elements, or as we think of new elements, such as helium and 

 radium emanation, which are formed by dissociation of radium. 

 As compared with chemical elements the factors of heredity are 

 probably very complex things and the new factors which appear in 

 the course of evolution probably arise as new combinations of 

 factors or parts of factors previously present. Nowhere in the 

 entire process of organic evolution is there any evidence that 

 new factors are "extrinsic additions" or are created de novo. 

 The whole process is one of evolution, that is of new combina- 

 tions of existing units, having new qualities which are the re- 

 sults of these new combinations. 



If these changes in the germ plasm may be induced by extrinsic 

 conditions, then a real experimental evolution will be possible; 

 if they cannot be so induced but are like the changes taking place 

 in the radium atom we can only look on while the evolutionary 

 processes proceed, selecting here and there a product which 

 nature gives us but being unable to initiate or control these pro- 

 cesses. 



B. CONTROL OF HUMAN HEREDITY: EUGENICS 



I. PAST EVOLUTION OF MAN 



There is every evidence that man also, no less than domesti- 

 cated animals, has evolved from a natural or wild state. The 

 most primitive types of men are known only from a few fossil 

 remains, which indicate that these primitive men belonged to dif- 

 ferent species, and some of them even to different genera, from 

 Homo sapiens (Fig. 101). Later stages in the evolution of man 



