550 HUMAN BIOLOGY 



industries. Machinery alone does not make a profitable 

 factory. There must be workmen to run the machines. 



It is possible that the findings regarding fertihty in this 

 country are not widely divergent from what theoretically 

 ought to be if our society is to continue in general prosperity 

 and well-being, and continue to grow in these respects. In 

 short do we not need to have laborers reproduce faster than 

 the first six occupations on our Hst, in order first to take up 

 the greater human wastage in the laboring classes, and second 

 to permit of continued industrial growth and prosperity? 

 Possibly a sound economic structure of the country as a 

 whole is in a very real and considerable sense dependent 

 upon just this relationship. 



The facts set forth in Table vii plainly mean that some part 

 of the next generation's supply of professors, doctors, 

 lawyers, bankers, railroad presidents, and the like, will have 

 to be recruited among the sons of the farmers and factory 

 laborers of this generation. But what of it? Just precisely 

 this relationship has always been true so far in the history 

 of the world and probably will be for a long time to come. And 

 furthermore from just the same sources will have to be 

 recruited some of the clerks, typists, small tradesmen, 

 job-holders, brakemen, motormen and various other citizens. 



In the United States the agricultural group has for a 

 long time produced far more than enough children to main- 

 tain its own industry. These farm boys have contributed in 

 no small measure to the highest intellectual, social, and 

 economic classes of our population. In fact the agricultural 

 class has demonstrated an especial fitness to contribute 

 sound stock to other occupational classes. It is possible 

 that time will show that the industrial class in our large 

 cities is, in already measurable and probably increasing 

 degree, doing the same thing. 



The falling birth rate and death rate and the type of 

 occupational differential fertility discussed here may perhaps 

 be regarded as adaptive regulatory responses, that is biolog- 

 ical responses, to alterations in the environment in which 

 human society lives. In this environment the economic 

 element is perhaps the most significant biologically. 



