HUMAN IMPLICATIONS 221 



Journal of Sociology indicate that the present opin- 

 ion is that the increase in the birth rate may be 

 the result of a campaign against abortion which in 

 pre-Nazi times terminated over one-third of the 

 pregnancies. (58, 125) One can deduce from general 

 biological experience, despite the current German 

 data, that the population almost automatically ad- 

 justs numbers within its physical and biological 

 limitations. Doubtless eventually this mysterious 

 process of population adjustment will be analyzed. 

 At present we have made some progress toward an 

 understanding of the factors involved in non-human 

 populations, but have little objective knowledge to 

 report where men are concerned. 



It is of course possible to increase the present 

 food supply of the world enormously. It has been 

 estimated that if our present biological knowledge 

 were consistently applied we could raise food enough 

 to supply at least ten times the present world popu- 

 lation, instead of the 25 per cent increase to which 

 we are looking forward by the year 2100. Presum- 

 ably by that time we shall have learned much more 

 than we now know about intensive methods of food 

 production. 



Let us take one simple instance only. In the 

 United States we are substituting gasoline-driven 

 farm machinery for horse power in agricultural work. 



