68 HEREDITY AND SOCIETY 



written have served but to emphasize their wisdom. 

 It is the quality of the population that matters. A 

 hardy, efficient and energetic race will live and create 

 surplus wealth in conditions where a less effective race 

 would starve. A weak, ineffective and indolent people 

 will make nothing of the most lavish natural resources. 



It seems clear that a selective birth-rate is one of the 

 most powerful agencies that can exist for modifying the 

 character of a race. But until recently the possibility 

 of variation had not occurred even to students of social 

 development, and without thought it was assumed by 

 historians, politicians and sociologists that whatever else 

 changed, the inward constitution of a people remained 

 unaltered throughout the centuries, so that the explana- 

 tion of any rise or fall in achievement had been sought 

 in external causes. In the light of modern knowledge, 

 the one assured fact is the constant variation in the 

 composition of a nation, and it is by a study of the 

 birth-rates of the component parts that we get some 

 clue to the progress of the internal movements. In 

 matters affecting population, as with the weather, it 

 should be possible for the Registrar-General to issue 

 some sort of reasoned forecast, even to hoist a storm- 

 warning. The quality and number of the births taking 

 place in one year will not produce the full effect for 

 another twenty or thirty, just as variations in baro- 

 metric pressure take twenty or thirty hours to bring 

 about the conditions they foretell. There is therefore 

 plenty of time to study the gathering of the clouds 

 and to prepare, if necessary, for the coming of the 

 whirlwind. 



