Mutationism

Mutationism is a theory of evolution, proposed as an alternative to evolution by natural selection both before and after Darwin's 1859 On the Origin of Species, holding that mutation itself is the source of evolutionary novelty and can create new forms or species suddenly, in a single jump. Before Darwin most biologists accepted a version of this saltationist view, but Darwin rejected it in favor of gradual change; in 1901 the geneticist Hugo de Vries revived saltational thinking with his mutationstheorie, based on his experiments with the evening primrose, and early geneticists including William Bateson, Thomas Hunt Morgan and Reginald Punnett initially treated mutationism as a rival to Darwinism. Later historians found that this picture oversimplified the record, since by around 1918 most mutationists had in fact accepted natural selection alongside mutation, and subsequent work showing that many genes acting together could produce continuous variation allowed Mendelian genetics and natural selection to be reconciled, with mutation now understood as the source of the variation on which selection acts. Although largely abandoned as a rival to natural selection, mutationism resurfaces periodically, most notably in Richard Goldschmidt's idea of hopeful monsters and in ongoing debate over the evolutionary importance of mutation.