The Mendelian and Non-Mendelian Origins of Genetics

The story of Gregor Mendel’s long neglect and rediscovery has been criticized for taking Mendel’s paper out of context, both in 1865, when he presented it to the Naturalists’ Society in Brno, and in 1900, when it became a cornerstone of genetics. But what are the proper contexts? Here a case is made for reading Mendel’s paper, in both time periods, as part of a large body of nineteenth-century literature on practical plantand animal breeding and experimental hybridization. This literature contained a confusing and contradictory assortment of observations on heredity and preliminary laws and generalizations, some in line with Mendel’s, but most not. In 1865, Mendel’s paper was intended as a modest attempt to begin to bring order to this chaos, but there was little reason to celebrate it as a breakthrough: too many “non-Mendelian” cases were known. After 1900, this literature was, in a sense, rediscovered along with Mendel, and it then played a dual role. For critics like W.F.R. Weldon, the non-Mendelian cases falsified Mendel’s laws. But for Mendel’s three co-rediscoverers, William Bateson, and others, they represented challenges to be met within a research program that would modify and extend Mendel’s system and establish a new scientific