486 READINGS IN EVOLUTION, GENETICS, AND EUGENICS 
Remembering that longevity is in general inherited, and that it is 
found in the families of all the people of this study (since one in each 
fraternity lived to be go or over) how is one to interpret this zero 
coefficient? Evidently it means that although these people had 
inherited a high degree of longevity, their deaths were brought about 
by causes which prevented the heredity from getting full expression. 
As far as hereditary potentialities are concerned, it can be said that all 
their deaths were due to accident, using that word in a broad sense to 
include all non-selective deaths by disease. If they had all been able 
to get the full benefit of their heredity, it would appear that each of 
these persons might have lived to 90 or more, as did the one in each 
family who was recorded by the Genealogical Record Office. Geneti- 
cally, these other deaths may be spoken of as premature. 
In an ordinary population, the age of death is determined to the 
extent of probably 50 per cent by heredity. In this selected long- 
lived population, heredity appears not to be responsible in any meas- 
urable degree whatsoever for the differences in age at death. 
The result may be expressed in another, and perhaps more striking, 
way. Of the 669 individuals studied, a hundred—namely, one child 
in each family—lived beyond go; and there were a few others who did. 
But some 550 of the group, though they had inherited the potentiality 
of reaching the average age of go, actually died somewhere around 60; 
they failed by at least one-third to live up to the promise of their 
inheritance. If we were to generalize from this single case, we would 
have to say that five-sixths of the population does not make the most 
of its physical inheritance. 
This is certainly a fact that discourages fatalistic optimism. The 
man who tells himself that, because of his magnificent inherited 
constitution, he can safely take any risk, is pretty sure to take too 
many risks and meet with a non-selective—i.e., genetically, a pre- 
mature—death, when he might in the nature of things have lived 
almost a generation longer. 
It should be remarked that most of the members of this group 
seem to have lived in a hard environment. They appear to belong 
predominantly to the lower strata of society; many of them are immi- 
grants and only a very few of them, to judge by a cursory inspection 
of the records, possessed more than moderate means. This necessi- 
tated a frugal and industrious life which in many ways was favorable 
to longevity but which may often have led to overexposure, overwork, 
lack of proper medical treatment, or other causes of a non-selective 
