"Eugenics and Society" (The Galton Lecture given to the Eugenics Society), by Julian S. Huxley, Eugenics Review (vol 28:1) (5)

1828. 16 The Eugenics Review effect of environment, we cannot be sure what differences between groups are due to inheritance. [italics]Eugenic Bearings of Environmental Influence[end italics] This point is of extreme importance in eugenics. For instance, it is well known that members of different social classes differ in their average of stature, physique and intelligence - all of them characters of the greatest evolutionary importance. I take one or two examples from Carr-Saunders.* In a sample of fourteen-year-old Liverpool schoolboys, the boys from a secondary school were on the average no less than 6 1/2 inches (over 10 per cent.) taller than those from a council school in a poor neighborhood; and differences in weight were equally marked. In a similar investigation in London, the "mental age" (as determined by intelligence tests) of boys from a superior school was far above that of boys from a school in a poor neighbourhood. Twelve-year-olds from the superior school had a mental age nearly a year above their real age, while those from the poor school were a whole year behind their real age - a difference of 15 per cent. Such differences are usually cited by eugenists as proof of real and considerable difference in genetic qualities. For instance, Professor Carr-Saunders, after quoting these facts, concludes that "so far as persons in this country are concerned, the mental differences which we observe, after stripping off the obvious acquirements in the form of knowledge of facts, habits, customs, manners, are due only in very small part to differences in the physical environment, and in a varying though never to a large degree to differences in the social environment, and for the greater part to inherited differences." And he draws the same general conclusion with regard to the physical differences. Yet in the few years since Professor Carr-Saunders' book was written, this conclusion has become extremely unlikely. For recent work has shown that vitamins and other accessory food-factors have physical and mental effects far [hairline rule across column] [footnote text] *Carr-Saunders, 1926, pp. 126, 97, 105. [resume text] transcending what we originally thought possible. In the early years of vitamin research, attention was concentrated upon the definitely pathological states resulting from total or almost total deprivation. During the last ten years, it has been shown that moderate insufficiency of these accessory food-factors will result in retardation of growth, stunting, lack of physical and mental energy, and reduced resistance to infectious disease. Even boys who by all ordinary canons were regarded as in fine health and well above the average in physique were shown to benefit both in growth and in energy from the addition of extra milk to their diet. Sir John Orr has shown that the diet actually consumed by the poorer classes in Aberdeen, when given in unlimited quantities to rats, results in poor physique, small litters, low expectation of life, and proneness to numerous diseases, while the same diet with the addition of various vitamins and mineral salts kept the animals in tip-top condition.* In the face of such facts, it is no longer legitimate to attribute the observed differences in physique and intelligence between social classes mainly to genetic factors. Genetic differences may of course exist; but the strong probability is that most of the differences are dependent on differences in nutrition. Further, the defective nutrition of the poorer classes is in part due to ignorance, but in a large measure to mere poverty. Until we equalize nutrition, or at least nutritional opportunity, we have no scientific or other right to assert the constitutional inferiority of any groups or classes because they are inferior in visible characters. The extreme importance of applying accurate methods to the problem is shown by the results of recent investigations on twins. As is well known, twins may be identical or monozygotic, always of the same sex and both derived from the same fertilized egg; or they may be fraternal or dizygotic, either of the like or unlike sex, and derived from two separate eggs. The former will have identical [hairline rule across column] [footnote] *Cited in Orr, 1936. [end]