THE BIRTH-RATE 59 



become 996, while at the end of a century 687, and 

 in two centuries 472, of their descendants will alone 

 be left. 



The birth-rate of other sections of our people is 

 still about 33, or 13 more than their higher death-rate 

 of about 20. In a year each 1000 will become 1013, 

 in a century, 3600, and in two centuries, about 13,000. 



The less prolific stock, if originally equal in number 

 to the other, would be but one in six at the end of a 

 hundred years, and in two hundred years it would be 

 but one in thirty of the population. It would be lost 

 in the descendants of the stocks of predominant fertility. 

 Hence the importance of encouraging early marriages 

 and large families in those sections of the people where 

 the hereditary qualities are good. Early marriages 

 tell in two ways. When the birth-rate is unrestricted, 

 they mean large families ; and they shorten the interval 

 between two generations, and thus lead once again to 

 a more rapid growth of population. 



Till about the year 1875 no artificial selection seems 

 to have arisen. Heron has shown that in 1851 the 

 rather higher age of marriage in the well-to-do parts 

 of London as compared with the poorer parts was 

 enough to explain the rather lower birth-rate. All 

 sections of the community were reproducing themselves 

 very nearly at their natural rates, save for the small 

 disturbing factor due to the rather higher average age 

 at marriage in the more wealthy classes. But since 

 1875 a serious change has arisen. 



In 1876 the average birth-rate in Great Britain was 

 some 36 per thousand of the population. From that 

 time it has steadily diminished, and in 1910 sank to 



