But what are the practical possibilities of improving a people by conscious selection? The lack of knowledge concerning heredity and the composition of the chromosomes of prospective parents is undoubtedly an obstacle, but breeders of livestock have accomplished results without this information. The obstacles lie rather in obtaining the necessary control, in the lack of agreement as to which combination of traits is desirable, and in the difficulty in mating of combining sentimental and spiritual values with biological values. The problem is one of research from which in time higher eugenic ideals may emerge.
Research Committee on Social Trends, Inc., Recent Social Trends in the United States  (xxiii)