Genetic principles in medicine and social science / by Lancelot Hogben.

  • Hogben, Lancelot Thomas, 1895-1975.
Date:
1931
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Genetic principles in medicine and social science / by Lancelot Hogben. Source: Wellcome Collection.

    19/240 (page 15)
    GENETIC PRINCIPLES IN MEDICINE AND SOCIAL SCIENCE CHAPTER I THE PROBLEM OF TWIN RESEMBLANCE § i Fifty years have passed since Galton drew from a study of thirty-five pairs of similar and twenty pairs of dissimilar twins the following conclusion which has been widely quoted in the discussion of human variability : We may therefore broadly conclude that the only circumstance within the range of those by which persons of similar conditions of life are affected, that is, capable of producing a marked effect on the character of adults, is illness or some accident which causes physical infirmity. The impression that all this leaves on the mind is one of some wonder whether nurture can do anything at all beyond giving instruction in professional training. There is no escape from the conclusion that nature prevails enormously over nurture when the differences of nurture do not exceed what is commonly to be found among persons of the same rank of society and in the same country. . . If we compare contemporary knowledge of hereditary transmission in animals with the information which was extant when Galton wrote his Inquiries into Human Faculty , two striking differences are manifest. One is that anecdotal sources of information have been rejected in favour of controlled experiment developed along the lines suggested by Mendel's pioneer labours. The other is a clearer recognition of the distinction between family resemblance and hereditary similarity. Galton was content to draw his conclusions from data based upon indirect sources of information, and he believed that coefficients of fraternal correlation necessarily measured the intensity of inheritance. To-day we have at our disposal a good deal of precise information about twin resemblance. In the field of animal biology fraternal correlation is no longer regarded as a measure of genetic similarity ; but the implications of a clear dis tinction between family resemblance and genetic similarity have been recognised as yet by few investigators in the field of social biology.