58 HEREDITY AND SOCIETY 



circumstances. If this underlying assumption be not 

 justified, if an artificial selection be introduced by a 

 voluntary restriction of the birth-rate, and if this cause 

 affect some sections of the race more than others, and 

 not in proportion to the results of natural selection, 

 our whole outlook is modified, and further consideration 

 is necessary. A study of the birth-rate, then, is of 

 fundamental importance in our inquiry, and must 

 precede any further treatment of the subject. 



Therefore it will be necessary once more to review 

 in short abstract some results and reflexions which are 

 set out in greater fulness in our book on The Family 

 and the Nation. 



If one element of the people reproduce itself faster 

 than the rest, it will dominate the average character 

 of the nation at an ever-increasing rate. A little 

 calculation will make this plain. We shall see later 

 that certain classes of the people now produce an 

 average of only three children to the fertile marriage. 

 In order that a population should maintain its numbers 

 unaltered it is necessary that four children should be 

 born to couples that have children at all. On the 

 average of large numbers, two of the four will die 

 early or have no offspring themselves, and the other 

 two are left to replace the parents. Thus a nation, 

 or section of a nation, that only produces three children 

 to the fertile marriage has a birth-rate only three- 

 quarters of that necessary to maintain its numbers 

 unchanged. If the death-rate be taken at 15 in 1000 

 per annum, the birth-rate will be f x 1 5, or about 1 1 ; 

 that is, about 4 less than the 15 needed to replace 

 the dead. At the end of a year the 1000 will have 



