DOMINANCE OF ECONOMICS OVER EUGENICS 141 



attitude towards women, vastly to ameliorate these afflictions of the female 

 sex, to reduce them, in fact, to the point where the compensations were 

 greater than the disadvantages. But there is no particular profit in better- 

 ing the lot of a slave. Meanwhile, intelligent and self-respecting women, 

 and those who value their husband's love, will use what means they may 

 have to restrict the size of their family to a very low level indeed. And in 

 this they will be right. The eugenist, from his glass house, cannot criticize 

 them. 



Another way in which our economic system acts to foil the true purposes 

 of eugenics is by masking the genetic constitution of individuals and of vast 

 groups through the gross inequalities of material and social environment 

 which it imposes upon them. The investigations of Burks on the resem- 

 blance between the intelligence of foster children and their guardians, 

 checked by the calculations of Wright on this material, and Newman's con- 

 verse findings concerning the considerable differences between the intelligence 

 quotients of genetically identical twins who were reared apart, show clearly 

 the important influence of environment as well as that of heredity upon 

 intelligence as ordinarily measured. In Burks' cases the usual differences 

 in home environment occurring between families of the type she studied 

 (mainly middle class) caused, on the average, a difference of about 6 points 

 in the child's Intelligence Quotient (on a scale in which 100 is the normal 

 I.Q.). This agrees as closely as could be expected with Newman's finding 

 that the differences in rearing between the members of his pairs of identical 

 twins reared apart usually caused as great I.Q. differences as did the differ- 

 ences in heredity of two non-identical brothers reared together, for just 

 about 6 or 8 points difference would be expected from the latter cause also. 

 Now in Newman's cases too the individuals compared (the members of a 

 pair) were reared in what was on the whole the same general social class. 

 Surely, the members of widely different social classes, such as Burks' 

 middle class people on the one hand, and white day laborers or Southern 

 Negroes or Mexicans, on the other hand, differ from one another, on the 

 average, in respect to environmental advantages by at least several times 

 the average difference between two members of the same class. Hence we 

 should expect I.Q. differences due to environmental dissimilarities between 

 the children of the former and the latter classes to average at least 15 or 20 

 points. And this is what has actually been found. 



The results, then, show us that there is no scientific basis for the conclusion 

 that socially lower classes, or technically less advanced races, really have a 

 genetically inferior intellectual equipment, since the differences found 

 between their averages are to be accounted for fully by the known effects 



