THE NUMBERS OF MEN 105 



While carbon is the keystone it is not the whole organic arch. 

 The story of annual net loss of the stuffs of life is similar for 

 other essential chemical elements. Lipman estimates that the 

 soils of the United States suffer the following annual net losses: 

 of nitrogen 2.7 million tons 5 of phosphorus 1.2 million tonsj 

 of potassium 30.7 million tonsj of calcium 43.2 million tonsj 

 of magnesium 14.2 million tonsj of sulphur 1.1 million tonsj 

 and of organic matter generally 222 million tons. 



Let it not be supposed that the problem concerns food alone, 

 or that mankind is scheduled to perish miserably by starvation 

 in the next fortnight. The problem of adequate food production 

 for the present or an even larger world population is not the 

 most serious aspect of the matter. The industrial and com- 

 mercial modes of life that are in an obligate way essential to 

 the maintenance of our dense urban populations are using up 

 their basic resources at an even faster rate than that of soil 

 exhaustion. To support a world increase of population of about 

 two and a half times between 1800 and 1918, coal, and pig iron 

 production had to be increased about a hundred-fold. 



There seems to the biologist some reason to believe that man- 

 kind is at the present time engaged in the process of biologically 

 adjusting or adapting itself to the situation that has developed 

 as the combined result of the growth of scientific knowledge and 

 the tremendously accelerated growth of population that that 

 increase in knowledge has fostered in the last three hundred 

 years. This adaptation appears to be going on in what must be 

 regarded as the normal biological way, namely by processes that 

 are not, for the most part, the resultants of conscious group 

 effort or planning, and may therefore be designated as natural, 

 insofar at least. Birth rates over a large part of the world are 

 generally falling, and have been falling for a considerable time 

 past. This decline in human reproduction is nowhere a conse- 

 quence as yet of a type of behavior deliberately planned by the 

 state for the whole mass of its people and deliberately forced 

 upon them J nor, on the best evidence, is it anywhere wholly 

 due to individual planning to reduce reproduction by birth 



