CHAPTER VII 
THE CAUSES OF THE DECLINING BIRTH RATE 
“Of the thirty-eight physicians [in New York] who were willing to 
discuss the matter I asked: ‘What do you find to be the ideal American 
family?’ Thirty said, ‘Two children, a boy and a girl;’ Six said ‘One 
child.’ One said, ‘Having a family is not an American ideal;’ and one 
said, ‘Five or six.’”—L. K. Commander, The American Idea. 
“T wouldn’t have another for the world. I had Lucy when I was 
first married and didn’t know.any better.”—Mrs. C. of New York. 
THE practical problem of remedying the evils of the present 
differential birth rate requires for its solution a knowledge of the 
causes by which this condition is brought about. Spencer attrib- 
uted the low birth rate among the intellectual classes to the 
“antagonism between Genesis and Individuation,”—the utiliza- 
tion of vital energy in cerebration being supposed to diminish, by 
a sort of compensating loss, the power of producing offspring. He 
admits that “special proofs that in man great cerebral expendi- 
ture diminishes or destroys generative power, are difficult to 
obtain.” Certainly cases enough might be adduced in which men 
of high intellectual power have shown no lack of fertility, but 
among women it seems more probable that intense and continued 
application to mental work might produce at least a partial 
sterility. A half century ago large families among the intellectual 
classes were not uncommon. The rapid decline of the birth rate 
within a couple of generations can scarcely depend upon any deep 
seated organic changes occurring in the human species. Our 
changed modes of life with their greater drafts upon nervous 
energy may have had a certain effect in reducing the natural 
fecundity of the female sex, but it is questionable if much of the 
decline in the birth rate can be attributed to this cause. 
In interpreting statistics concerning the number of births per 
thousand of the population, we must consider the effect of de- 
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