EVOLUTION OF THE HUMAN SPECIES 153 



established in another section; for if evolution is uni- 

 versally true, the main conclusion in any case must 

 assist the investigation of another, just as comparative 

 anatomy and embryology supplement and corroborate 

 each other in the larger survey of organic evolution. As 

 before, the illustrations of each department of the subject 

 must be selected from the stock of everyday observation 

 and information that we already possess, for we gain 

 much when we realize that evolution includes all the 

 happenings of everyday life and thought, as well as the 

 occurrences of the remote past. 



For the present, then, the questions relating to the 

 higher aspects of human life must be put aside, only 

 that they may be taken up at the last. Social evolu- 

 tion likewise finds its place in a later section, after the 

 phenomena of mind and mental evolution receive due 

 attention and description. At the present juncture, 

 the human species presents itself as a subject for organic 

 analysis and classification, merely as a physical organ- 

 ism. Just as the study of locomotives must begin with 

 the detailed structure of machines in the workshop 

 before they can be profitably understood as working 

 mechanisms, so the physical evolution of mankind must 

 first be made intelligible before it is possible to prosecute 

 successfully the studies dealing with the psychology, 

 social relations, and higher conceptions that seem at 

 first to be the exclusive properties of our species. 



The problems of physical evolution of man and of 

 men fall into two groups. Those of the first deal with 

 the origin of the human species as a unit, and its com- 

 parative relation to lower organisms, while those of 

 the second part are concerned with the further evolu- 



