HUMAN LONGEVITY 51 



folk compare with that of the elite group of extraordinary 

 long-livers, the nonagenarians and centenarians? Figure 5 gives 

 the answer in graphic form. 



From this diagram it is seen that, on the average, each single 

 immediate ancestor, father, mother, grandfather, or grand- 

 mother, of the extremely longevous persons of panel A on the 

 left side was longer-lived than the corresponding ancestor of 

 the ordinary persons of panel B on the right side. Thus the 

 fathers of the longevous died at an average age of 72.4 years. 

 This was 12.3 years older, or over 20 per cent, than the average 

 age of the fathers of the panel B folk at the right end of the 

 chart. The central panel A — B, gives the differences, in abso- 

 lute numbers of years (upper figures in each sex sign) and as 

 percentages of the panel B means, for each category of the six 

 immediate ancestors. 



From this chart two results indubitably emerge regarding 

 the influence of heredity upon longevity, namely: 



First: People who achieve extreme longevity have immediate 

 ancestors (parents and grandparents) who are, on the average, 

 definitely longer-lived than the corresponding ancestors of the 

 general run of the population. This is true without exception 

 for each particular category of immediate ancestors. 



Second: This hereditary influence promoting longevity is be- 

 tween two and three times as great relatively for parents as 

 it is for grandparents, so far as the results of this investigation 

 indicate. 



It appears, then, that old Dr. Holmes was sound in his 

 advice to select long-lived parents, and particularly long-lived 

 mothers. 



Let us now go a little deeper into the matter, by proceeding 

 to examine more specifically how each of the parents of the 

 extremely longevous persons was bred relative to longevity, as 

 compared with the parents of the general run of folk. For the 

 purposes of this inquiry let us regard an individual who dies 

 under fifty years of age as short-lived j one who dies between 

 fifty and sixty-nine years as average or mediocre in life dura- 



