achieved by these geneticists spanned the action of natural selection on alleles (alternative forms of a gene), the Hardy–Weinberg equilibrium, the evolution of continuously-varying traits (like height), and the probability that a new mutation will become fixed. In this view, the early geneticists accepted natural selection alongside mutation, but rejected Darwin's non-Mendelian ideas about variation and heredity, and the synthesis began soon after 1900. The traditional claim that Mendelians rejected the idea of continuous variation outright is simply false; as early as 1902, Bateson and Edith Saunders wrote that "If there were even so few as, say, four or five pairs of possible allelomorphs, the various homo- and hetero-zygous combinations might, on seriation, give so near an approach to a continuous curve, that the purity of the elements would be unsuspected". Historians have interpreted the history of mutationism in different ways.The classical view is that mutationism, opposed to Darwin's gradualism, was an obvious error; the decades-long delay in synthesizing genetics and Darwinism is an "inexplicable embarrassment"; genetics led logically to the modern synthesis and mutationism was one of several anti-Darwinian "blind alleys" separate from the main line leading from Darwin to the present. A revisionist view is that mutationists accepted both mutation and selection, with broadly the same roles they have today, and early on accepted and indeed offered a correct explanation for continuous variation based on multiple genes, paving the way for gradual evolution. At the time of the Darwin centennial in Cambridge in 1909, mutationism and Lamarckism were contrasted with natural selection as competing ideas; 50 years later, at the 1959 University of Chicago centennial of the publication of On the Origin of Species, mutationism was no longer seriously considered. See also History of evolutionary thought Rapid modes of evolution Notes References Sources Bateman, Richard M.; DiMichele, William A. (2002). Generating and Filtering Major Phenotypic Novelties, NeoGoldschmidtian Saltation Revisited. In Cronk, Q. C. B.; Bateman R. M.; Hawkins J. A. eds. Developmental Genetics and Plant Evolution. London: Taylor and Francis. pp. 109–159. Bateson, William. (1894). Materials for the Study of Variation: Treated with Especial Regard to Discontinuity in the Origin of Species. Macmillan. Biology theories Evolutionary biology Molecular evolution Mutation