History of Genetics

Alongside the developing experimental tradition of the biologists, the nineteenth century saw increasing attention given to family histories (genealogy) and to population studies (biometry). Both owed their popularity to the growing concerns about human heredity. Was increasing urbanization affecting the quality of human heredity as evidenced by the increasing numbers of the insane, the tubercular, the alcoholic? Supporting this concern was the medical concept of a diathesis—that is, the predisposing to certain diseases, especially those chronic conditions like gout, epilepsy, asthma, tuberculosis, and cancer, that are often manifested later in life. Diatheses were judged to be features of a person's hereditary constitution. Although the tuberculous diathesis was not banished by Robert Koch's isolation of the tubercle bacillus in 1882, it did become transformed into the genetic susceptibility to the pathogen.

Genealogy became of special interest for several reasons. Many an aspiring family in Napoleonic Europe, wishing to claim the status of majorat (Napoleon I's substitute for aristocracy), needed to provide their family genealogies as evidence of the fraction of "blue blood" in their ancestry. In Jamaica the fractional theory was used to draw the line between those descended from mulattos who could and could not be considered white. Hence the classification: mulatto, half black; terceron, one-quarter; quateron, one-eighth; quinteron, one-sixteenth. In England, Francis Galton, concerned about what he saw as a growing mediocrity in urban populations, used genealogy to argue for the inheritance of what he called "genius"—exceptional ability that is inborn. Such he found in families like the Bachs, Bernoullis, and Darwins and thought to find especially among judges. In the early years of the twentieth century, with the advent of Mendelism, the hunt for pedigrees that exemplified Mendelian heredity was all the rage. Hereditary night blindness offered the most extensive pedigree, but many were the studies of the familial incidence of feeblemindedness, inebriation, epilepsy, pauperism, and criminality. Concerns about degeneration of the European races, and the felt need to apply science to the problem, provided a political climate in which Galton decided in 1904 he could launch his bid for the science he had earlier (1883) called "eugenics" and defined as "the science of improving the stock … which, especially in the case of man, takes cognizance of all the influences that tend in however remote a degree to give to the more suitable races or strains of blood, a better chance of prevailing speedily over the less suitable than they otherwise would have" (Human Faculty, p. 17).

The stark hereditarian leaning of Galton did not go un-challenged. His first book, Hereditary Genius (1869), received mixed reviews, the accuracy of his biographical data coming under fire. In Switzerland, Alphonse de Candolle argued persuasively for the effects of the educational, cultural, and political climate, rather than heredity, to account for the remarkably high representation of Swiss scientists among foreign members of the Royal Society and the Académie des Sciences. In this way de Candolle countered the emphasis Galton had placed on heredity in his work English Men of Science (1874). As for the enthusiasts for eugenics, both those in the biometric tradition of Galton and the experimental tradition of Mendel were for the most part supportive. One Mendelian who adopted a more cautious position was William Bateson. Though an elitist, he judged the scientific basis of many of the eugenists' claims inadequate and kept his group of coworkers at a distance from the eugenically inspired Mendel Society that had formed in England during the early years of Mendelism. As an hereditarian, of course, Bateson was concerned that those carrying harmful genes should be discouraged from bearing offspring. He was thus a supporter of negative eugenics. But as to positive eugenics—the encouraging of selected individuals to mate and have offspring—he was not clear what particular traits should be looked for.