180 DOCTRINE OF EVOLUTION 



task is relatively simple when it is concerned with recent 

 times where the aid of written history may be sum- 

 moned ; but when the events of remote and prehistoric 

 ages are to be placed in order, the difficulties seem well- 

 nigh insuperable. All is not known, nor can it ever be 

 known ; but wherever facts can be established, science 

 can deal with them. By a study of the present races 

 of mankind, much of their earlier history can be worked 

 out, for their genetic relations may be determined *by 

 employing the principle that likeness means consanguin- 

 ity. Let us suppose an alien visitor to reach our planet 

 from somewhere else; if he were endowed with only 

 ordinary human common-sense, he would very soon 

 ascertain the common origin of the English-speaking 

 people in Canada, the United States, Australia and 

 New Zealand, South Africa, and many other places. 

 Even if he could not understand a word of the English 

 language, he would be justified in regarding them all as 

 the descendants of common ancestors because they 

 agree in so many physical qualities. The anthropologist 

 works according to the same common-sense principle, 

 obtaining results that find no explanation other than 

 evolution when the varying characters that are used to 

 determine social relationship are properly classified and 

 related. It is to these characters that we must now 

 give some attention. 



The average stature of adults varies in different races 

 from four feet one inch in certain blacks to nearly six 

 feet and seven inches, as among the Patagonians. 

 These are the extreme values for normal averages, 



