INFLUENCE OF ORDER OF BIRTH, ETC. 321 
which have often been quoted in discussions of this subject. 
Among the parents of 456 criminals it was found that both young 
and old parents produced more criminals than were born from 
people of maturity (20-40 years). Thieves predominate among 
the children of young parents while swindlers and those guilty 
of crimes of violence were more common among the children of 
parents of over 40 years. Studies of the intelligence of 917 
school children in relation to the age of their fathers gave a high 
percentage with good intelligence from fathers below 25 years. 
The children of young mothers (21 years or less) were found to 
produce about as high percentage of intelligent pupils as the 
children of young fathers. The very superior children, however, 
were somewhat more frequently born of parents of mature age. 
Children of old parents made in general the poorest showing. 
However, the children of old fathers made the best record in 
respect to conduct at school, but curiously enough the children 
of older mothers were the worst of all. It is noteworthy that 
the relation between intelligence of offspring and age of parents 
is just the reverse of what it is claimed by Redfield, and the 
relation of crime to parental age seems to be at variance with 
the findings of Goring who found that criminals were especially 
frequent among the first born. 
There is so much opportunity for social factors to affect such 
results as were found by Marro that any real biological influence 
of parental age is not apparent. Grouping of parents into young 
and old necessarily involves to a certain degree a selection of 
stock. This circumstance together with the environmental factors 
which are also more or less different for the children of old 
and young parents may influence to a considerable degree the 
intelligence and conduct of school children and even proclivities 
to crime in later years. 
Undue frequency of births is undoubtedly correlated with 
the high early death rate of children. Data compiled by Ansell 
from well-to-do English families showed that where the interval 
between births was less than a year the infant mortality was 
nearly twice as great as when the interval was between one and 
