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Fig. 17. Diagram to illustrate alternative hypotheses as to the history of the 

 human population of the earth. The portions of the curve drawn in broken lines 

 are purely hypothetical, except as to the total time scale. The portions of the 

 curves depicted by a continuous solid line (1630-1930) represent the known 

 facts as to world population growth, and are plotted to the same time scale as 



the earlier portion 



