NATURAL SELECTION IN MAN 197 



to be impressed with the fact that sentiment has considerably 

 influenced opinion on the purely matter of fact problem as to 

 whether the infantile death rate is or is not selective. The prob- 

 lem of how far selection occurs in the early periods of life is one 

 of great difficulty and it is especially important that it be ap- 

 proached in an entirely unbiased spirit. In attacking it by statis- 

 tical methods it is necessary to be continually on one's guard 

 against falling into the many pitfalls which lie across our path. 



One method by which the problem has been attacked is to 

 ascertain the relation between high infant mortality and the 

 expectation of life among the survivors. Several investigators 

 (von Erben, Bleicher, Gottstein and Rahts) have reported that a 

 high infant or child mortality is followed by a relatively low 

 mortality in later life. On the other hand, Newsholme in an 

 elaborate comparison of the infant and child death rates over 

 several districts of England has found that where there is a high 

 infant death rate there is also a high death rate of all children up 

 to the period of adolescence. Koppe has found a high infant 

 mortality correlated with a high death rate in the second year, 

 and Prinzing has found a similar correlation between death in the 

 first year and deaths from i to 4 years of age. Sadayuki's results 

 show that in separate provinces of Germany a high infantile and a 

 high child death rate go together. Other investigators (Prinzing, 

 V. Vogt, Peiger, Mullhausen) have found (contra Grassl) high 

 infant mortality to be correlated with inferiority of recruits 

 for military service. 



Those who have concluded from these results, as several have 

 done, that the infant death rate cannot be selective have drawn 

 an unwarranted inference. Many conditions which produce a 

 high infantile death rate are apt to cause a high death rate also in 

 childhood and adolescence. Ignorance, poverty, epidemic dis- 

 eases and unsanitary surroundings take their toll from people of 

 all ages, and the fact that the period beyond infancy is not spared 

 because the first year of fife is unduly crowded with fatalities, 

 in no way proves that the death rate is not selective during the 

 whole period. It is not a fair test of the potency of selection to 



