502 



EVOLUTION, GENETICS, AND EUGENICS 



It is not by accident that inherited longevity in a family is associ 

 ated with low mortality of its children. The connection between th >. 

 two facts was first discovered by Mary Beeton and Karl Pearson ii> 

 their pioneer work on the inheritance of duration of life. They found 

 that high infant mortality was associated with early death of parents, 

 while the offspring of long-lived parents showed few deaths in child- 

 hood. The correlation of the two facts was quite regular, as will be 

 evident from a glance at the following tables prepared by A. Ploetz: 



LENGTH OF LIFE OF MOTHERS AND CHILD MORTALITY OF THEIR 



DAUGHTERS (ENGLISH QUAKER FAMILIES, DATA OF 



BEETON AND PEARSON, ARRANGED BY PLOETZ) 



Year of Life in Which Mothers Dikd 



to 38 



39-S3 



54-68 



69-83 



84 up 



At 

 All 



Ages 



Number of daughters 



Number of them who died in first five 



years 



Per cent of daughters who died. . 



234 



122 

 521 



304 



114 



37-5 



395 



118 

 29.9 



666 



131 

 19.7 



247 



26 

 lo.s 



1,846 



511 



27.7 



LENGTH OF LIFE OF FATHERS AND CHILD MORTALITY OF 



THEIR DAUGHTERS 



Number of daughters 



Number of them who died in first five 



years 



Per cent of daughters who died. . 



To save space, we do not show the relation between parent and 

 son ; it is similar to that of parent and daughter which is shown in the 

 preceding tables. In making comparison with the 340 famihes from 

 the Genealogical Record Office, above studied, it must be noted that 

 Dr. Ploetz's tables include one year longer in the period of child mor- 

 tality, being computed for the first five years of life instead of the first 

 four. His percentages would therefore be somewhat lower if com- 

 puted on the basis used in the American work. 



These various data demonstrate the existence of a considerable 

 correlation between short life {brachybioty, Karl Pearson calls it) in 

 parent and short life in offspring. Not only is the tendency to live 

 long inherited, but the tendency not to live long is likewise inherited. 



