INFLUENCE OF ORDER OF BIRTH, ETC. 317 
ranks, and finds that the sons of old fathers live longer than the 
sons of young fathers. He also studied the longevity of 1,104 
persons from families of four or more children who lived to adult 
life. From these persons ‘“‘among whom those having high birth 
ranks were brothers and sisters of those having low birth ranks, 
it was found that there was a very uniform increase in length of 
life as birth ranks grew higher,” an addition of four years to the 
age of the father added one year to the life of the child. 
In regard to the parentage of great men, Redfield remarks: 
“Tt may be argued that the sons of old men are necessarily the 
sons of long lived parents, while the sons of young men are the 
sons of both long lived and short lived parents, and consequently 
cannot be expected to live so long on an average.” This objec- 
tion, while sounding reasonable, Redfield attempts to show is 
fallacious. In order to do so he selected from the Redfield gene- 
alogy “every family which had four or more sons who reached 
maturity and who did not lose their lives because of war or 
accident.” The average life of the different sons is indicated as 
follows: 
Eldest Son 2nd Son 3rd Son = 4th Son 
VAS uicd vy cieved aiaaus atts 60.85 69.14 69.85 71.14 
“There can be no selection in this case,” says Redfield, “ because 
the different sons of the family are sons of identical parents, and 
not sons of different or selected parents.” 
Despite the plausibility of his contention I cannot feel sure 
that Redfield has succeeded in avoiding our deceptive enemy, the 
statistical fallacy. If he has averaged together the ages of sons 
belonging to fathers of certain age groups without regard to date 
of marriage or other circumstances, he may have obtained quite 
misleading results. Young parents marry early and older parents 
as a class must contain many who married late and whose four 
children, therefore, belong to the later part of their reproductive 
period. It is possible to have a number of families in each of 
which the age of successively born children regularly diminishes 
and yet when the ages of the children are averaged together there 
