3i6 THE TREND OF THE RACE 



mothers (20 or less) are shorter and lighter than the children of 

 mothers a few years older. In mothers over 25 the height and 

 weight of children diminished with advancing age. A somewhat 

 similar relationship is seen in children at 13.5 years. The data of 

 Professor Ewart, since they deal with only a few hundred cases of 

 mixed stocks, are entirely inadequate to solve the problem of how 

 age of parents affects the offspring in later years. In such an 

 investigation there are several sources of fallacious conclusions. 

 Consider for instance the presence of a number of Italians in the 

 population studied. The ItaHans are characterized by short 

 stature and they are prone to marry early. The children of 

 young mothers would be apt to include a relatively large propor- 

 tion of ItaHan stock. Now if we compare the height of these 

 children in later life with the average height of children of older 

 parents we might be misled into attributing to parental age a 

 characteristic really dependent upon race. Children of older 

 parents are, other things equal, members of larger families than 

 children of young parents. Large families tend to characterize 

 stocks in the lower walks of life in which the surroundings are less 

 hygienic and in which conditions for growth are less favorable 

 than among people with small families. By taking a random lot 

 of children begotten by old parents we should get a proportion- 

 ately large number of children from large families, especially since 

 the relatively recent reduction of the birth rate has occurred 

 mainly through preventing the arrival of those who would be later 

 born children. Selecting the children of old parents, therefore, 

 incidentally involves also a selection of stocks and to a certain 

 degree also a selection of environments. These sources of erro- 

 neous interpretation of statistics, — to say nothing of others — 

 must be borne in mind in the study of our problem. 



Mr. Redfield has reported investigations on the influences 

 of parental age on longevity of offspring which led him to con- 

 clude that children begotten when their parents are old live 

 longer, on the average, than children who are the product of their 

 parents' earlier years. He has calculated the length of life of all 

 the great men of whom he could obtain a record of the birth 



