Parental Age Effects on Man 



23 



long time period. In this study, therefore, no attention has 

 been paid to observance of the 100-year span. The expecta- 

 tion of Hfe was calculated for different maternal ages at the 

 birth of the children, notwithstanding the excess of short- 

 lived among those born in the latter half of the 19th century. 

 It was assumed that this would give erroneous absolute 

 values for the total expectation of life but that it would not 

 affect the parental age effects. In order to determine whether 



50 



40 

 30- 

 920 



UJ 



t 



10 



Total material 



50 

 40 

 30 



o 



II 



■X 



LU 



T 



Born_ before 1830 



Total material 

 cT 



20h 

 j^All parities 

 2 Second and subsequent children 



S2A 25-29 30-36 35-39 S40 ^24 25-29 30-34 35-39 ^40 



Maternal age, years 



Fig. 2. Mean length of life {Ex=o) in various maternal age groups of 

 boys and girls born before 1830 (12,786) and in the whole series (17,980). 



this assumption was justified the relative number of the 

 mothers in various maternal age groups, in those born before 

 and after 1830, respectively, was calculated. The result is 

 shown in Fig. 1. As may be seen, the distribution is not 

 uniform: among tnose born after 1830 the number of young 

 mothers is smaller than in those born before 1830. The 

 deficit is evenly compensated for by the other maternal age 

 groups. This means that there is a bias in the expectation of 

 life in favour of the progeny of the youngest mothers. Fig. 2 

 records the expectation of life calculated for those born before 

 1830 and for the whole material. It seems evident that most 



