The Genetic Analysis of Continuous Variables in Man

At the Third International Congress of Human Genetics, Thoday lamented the fact that “we are making very little real progress in the understanding of continuous variation in man” (Thoday, 1967). The remarkable advances that have been made over the last twenty years, particularly in human biochemical genetics and also in many other aspects of the genetics of man, have not been paralleled in the genetic analysis of quantitative traits. Indeed, researchers in other subjects (and here I am thinking particularly of sociologists and psychologists) seeking guidance on the genetics of continuous variables, can be excused for believing that progress since Galton’s classic studies (Galton, 1889) provided the basis for human genetics, has been merely honing and polishing a very imperfect model rather than innovatory.