368 EVOLUTION AND GENETICS 



likely to result in the reappearance of the defect, while marriage 

 of the heterozygous members of a line to members of normal lines 

 would be certain to keep any but a sex-linked character submerged 

 and might even eliminate it entirely. 



The same must l^e said of desirable and indifferent qualities. 

 Whether evident or not a character is much more likely to be 

 preserved through the mating of closely related individuals than 

 through the crossing of different strains. 



It is fortunate that modern social customs do not favor cousin 

 marriages, although they are tolerated as the closest permissible 

 inbreeding. Such an attitude tends to prevent the expression of 

 inherent defects. Even though good and bad alike are perpetuated 

 through inbreeding it is doul^tful that the benefits derived from 

 the marriage of closel}'^ related persons are sufficient to offset the 

 risks. 



A moderate degree of inbreeding cannot be avoided, but the 

 persons involved are usually so remotely related that the effect 

 is practically the same as that of marriages within a social or 

 intellectual class. Too great contrast between individuals is 

 inimical to happy married life, and happiness must remain a 

 fundamental consideration in this important relationship. Like 

 will continue to seek like and to beget like. The latter process 

 is the one certain result, whether good or bad, of inbreeding. 



The Jukes. Several families have become famous in connec- 

 tion with the study of human heredity, among them the Jukes. 

 The history of this family was first reported by Dugdale in 1875 

 and more recently by Estabrook in 1916. Dugdale's interest was 

 first aroused by the frequent recurrence of the same name (the 

 name Jukes is fictitious) in prison records. His original investiga- 

 tions covered 709 individuals of whom " 180 were paupers or had 

 received poor relief to the extent of 800 years, 60 were habitual 

 thieves, 50 prostitutes, 7 murderers, and the total cost to the 

 state was estimated at $1,308,000.00" (Holmes). 



When Estabrook monographed the family in 1916 he was able 

 to report on 2,094 individuals, of whom not more than one-half 

 were living. The general quality of the family was the same as 

 in its earlier years. Criminal records, intemperance, pauperism, 

 and prostitution abound in the story of these people. Feeble- 

 mindedness is very common, especially among the criminal mem- 

 bers of the family, and combinations of feeble-mindedness, ille- 



