Data for the Problem of Evolution in Man. 



161 



Fathers. Length of Life and Size of Family. 



Series III. The great bulk of the data was extracted from the 

 American Whitney Family. Here the features noted for the women 

 were again observed in the men, but to a much less marked degree. 

 There was a rather high maximum frequency of death at 45,* but not 

 so high as the maximum at 75, and the average age at death was some- 

 what lower than we find for the general English population. On the 

 whole the series is a very good one. 



Series IV. Extracted from Burke's ' Landed Gentry.' It has been 

 stated elsewhere! that this is a good class for such data. It possesses 

 a higher average fertility than the Peerage, and is a class in which 

 there is probably comparatively little artificial restriction. Unfortu- 

 nately it offers no material for the age at death of women. 



3. The following are the chief results obtained from the reduction of 

 these series : 



I. Table of General Results. 



In this table the unit for the standard deviation of the age at death 

 is 5 years, the unit of the grouping in the accompanying tables. Thus 

 age at death of mothers 35 gives the frequency of all the group of 

 mothers dying between 32 '5 and 37 '5. Of course the age at death of 

 certain parents would lie exactly on the boundary of a group, but such 

 exact information is very rarely forthcoming, and when it is in a few 

 cases forthcoming, i.e., the day of both birth and death is given, it is 

 very improbable that the age of death exactly bisects the year. Thus 

 no fractionising was found necessary in the first three tables. In the 

 ' Landed Gentry,' owing to the nature of the record, Mr. Yule found 

 a small amount of fractionising necessary, and this appears in the table 

 for Series IV. In the regression coefficients above tabulated 5 years is 

 again the unit, and the coefficient of regression is the constant by which 



* The existence of a modal Talue about 45 has been already noted io the 

 resolution of the mortality curve; it is the mode of the middle age mortality 

 component. See ' Phil. Trans.,' A, vol. 186, p. 403, and Plate 16. 



t ' Phil. Trans.,' A, vol. 192, p. 257. 



x 2 



