150 THE FAMILY AND THE NATION 



the more intense elements of adventurous energy, 

 both in action and thought, had been eliminated. 



If Greece, Rome, and Spain give us the best 

 examples of the catastrophic downfall of mighty States, 

 equally instructive instances of the action of unnatural 

 selection may be traced among almost all nations. 



The historical course of events seems to have run 

 so clearly in recurring cycles, that a general impression 

 of some common underlying cause is forced on the 

 mind. In the light of our present knowledge, the 

 process may be described in general terms. 



Left to itself, in quiet times a nation is subject to 

 the operation of natural selection. The better classes 

 establish a dominant fertility, and the unsound stocks 

 tend to be bred out of the race. By marriages and 

 intermarriages among the more capable sections of the 

 community, ability of various sorts and other effective 

 qualities become collected in certain definite families 

 throughout the people. An opportunity arises for 

 national development political, military, economic, or 

 intellectual and the families or individuals of appro- 

 priate ability rise to the occasion from all ranks. 

 Hitherto, in the history of nations, stagnation has 

 followed energy, a period of dulness has succeeded 

 brilliant intellectual output. How far is this ebb of 

 the tide historically explicable by our present line of 

 thought ? Doubtless the material for rapid advance gets 

 used up, and some slackening of speed is necessary ; 

 but, in the actual historical cases, cannot we trace another 

 cause, more subtle, more potent, and more secret ? 



The three great periods of economic and intellec- 



