THE 



AMERICAN NATURALIST 



Vol. LIV. January- February, 1920 No. 630 



CERTAIN EVOLUTIONARY ASPECTS OF HUMAN 

 MORTALITY RATES 1 

 PROFESSOR RAYMOND PEARL 

 The Johns Hopkins University 



It is the purpose of this paper to set forth some facts 

 regarding human mortality which appear to lead with 

 great clarity to certain evolutionary generalizations of 

 interest to the biologist, which have hitherto been over- 

 looked so far as I am aware. The present fashion in the 

 study of evolution is towards the analytical discussion of 

 the factors. Synthetic general discussions of broad 

 phases of organic evolution, which occupied so prominent 

 a place in early post-Darwinian times, are now but rarely 

 found in biological literature. This may fairly be re- 

 garded as a blessing, but perhaps not an entirely un- 

 mitigated one. While much of the general discussion of 

 evolution of the period of fifty years ago was utter non- 

 sense, still a view of some of the aspects of the forest may 

 be at least occasionally stimulating, and particularly in 

 these present days when we are accumulating such a 

 mass of precise data about the characteristics of the trees. 



It is in some ways remarkable that so little thought and 

 interest have been given by general biologists to the 

 phases of biology which form the working material of that 

 branch of applied science which is roughly but still suffi- 

 ciently intelligibly labelled "vital statistics.'' The data 



