SOME ASPECTS OF THE BIOLOGY OF HUMAN POPULATIONS 549 



excess of their representation in the population. From this 

 excess must necessarily be supplied the deficiencies in the 

 first six classes in the next generation, if these classes are 

 to maintain about the same representation in the total 

 population that they exhibit in the present generation. 



In a theoretically ideal social organization there would 

 presumably be a constant relative number of persons 

 engaged in each of the numerous differentiated occupations, 

 which when integrated together are essential to the well- 

 being and survival of the society as a whole. There is theoreti- 

 cally a fixed proportion of teachers, lawyers, store-keepers, 

 laborers, soldiers and so on, necessary to the most economic 

 functioning of the whole social organism. But in actual 

 human societies there is no extraneous autocratic determina- 

 tion of these occupational classes. Instead the actual existing 

 number is determined by a process of natural selection, 

 in which processes economic factors are probably the most 

 important element. 



But another factor comes also into the case. The human 

 units wear out faster in some occupations than in others, 

 and therefore need to be replaced faster. Also this is not 

 only an industrial country, but a country in which the 

 increase of prosperity and well-being is apparently almost 

 solely dependent now, has been for some time in the past, 

 and presumably will be for some time in the future, upon 

 the continued growth of industry. 



In order to permit the population to increase roughly 

 two and a half times, and enjoy the standards of living 

 which prevail at the present time, it has been necessary to 

 increase coal and pig iron production from 50 to 70 times, the 

 cotton production 20 times, the railway mileage 3000 fold, 

 and so on. It is only because the organization of industrial 

 processes, inventions, and scientific discoveries have made 

 possible the growth of industry of all sorts at the rates 

 indicated that human beings have been able to enjoy the 

 standard of living that they have and do, and at the same 

 time permit the population to grow as it has. 



These facts suggest further that all along there has 

 had to be an increasing production of laborers, skilled 

 and unskilled, in the manufacturing and mechanical 



