162 Dynamic Evolution 



names are given. That the average age of the 

 fathers of these men should be 55 years is 

 impressive. To find "contrary cases," it 

 would be necessary to find ten men of similar 

 mental greatness who were sons of fathers 

 averaging less than 25 years. None such ever 

 existed. 



Pedigrees of horses, dogs, and cows can 

 be made complete for four or five generations, 

 and we can examine in detail the different 

 animals in each pedigree for the purpose of 

 seeing in what way and to what extent 

 energy was concentrated or dissipated. Simi- 

 lar pedigrees of eminent men can rarely be 

 written because the facts are far in the past 

 and are not recorded. The best we can ordi- 

 narily do is to tabulate and examine the 

 length of time occupied in two generations 

 in the male line, and the number of cases in 

 which this can be done is quite limited. As a 

 preliminary it is necessary to furnish a table 

 showing the normal lengths of time from 

 births of grandfathers to births of grandsons, 

 and then make a comparison with this table. 



