INTRODUCTION 19 



relatives, have been omitted designedly. Numerous data 

 of these types have been available for many years, but 

 they have been of little service in clarifying the situation. 

 This is not altogether due to their fragmentary character 

 in point of time, or even to the fact that they usually lack 

 the precision necessary in data to be used in the analysis 

 of such complex phenomena. Data for a limited number 

 of generations are often useful, and precision is a relative 

 matter. The truth is, the majority of these records was 

 collected without regard to the type of fact required, and 

 without reduction to concrete numerical terms. In other 

 words, in records otherwise accurate, critical data are 

 omitted ; and those given are relatively useless on account 

 of their form. 



A detailed application of our conclusions to sociology, 

 agriculture and evolutionary theory has not been at- 

 tempted. It is hoped that the suggestions along these 

 various lines are sufficient to show how such application 

 can be made; but human direction of evolution either in 

 man or in the lower organisms is beset with difficulties so 

 numerous and so prodigious that each problem must have 

 its individual solution. 



