Macromutation

Mutationism, known before 1900 as saltationism, is the set of views of evolution that emphasizes the role of large mutations capable of causing sudden jumps including immediate speciation. It is one of several alternatives to Darwinism that have existed both before and after the publication of Charles Darwin's 1859 book, On the Origin of Species, which was gradualist. Mutation is seen as the source of novelty; if natural selection is considered, it is not seen as creative, and the direction of evolution is understood to reflect both mutation and selection.

Saltationism was the common view before Darwin; in 1822 Étienne Geoffroy Saint-Hilaire argued that species could be formed by sudden transformations. Darwin opposed saltation, insisting on gradualism in evolution as in geology. In 1864, Albert von Kölliker revived Geoffroy's theory. In 1901 the geneticist Hugo de Vries gave the name "mutation" to seemingly new forms that suddenly arose in his experiments on the evening primrose Oenothera lamarckiana, and by 1909, mutationism became a rival to Darwinism supported by early geneticists including William Bateson, Thomas Hunt Morgan, and Reginald Punnett.

Mutationism, along with other alternatives to Darwinism like Lamarckism and orthogenesis, was discarded by most biologists in the modern synthesis of genetics and evolution of the early 20th century; mutation took its place as a source of the variation essential for natural selection to work on. However, in 1940, Richard Goldschmidt again argued for single-step speciation by macromutation, describing the organisms thus produced as "hopeful monsters", earning widespread ridicule. In 1987, Masatoshi Nei argued controversially that evolution was often mutation-limited. Saltation is seen to occur at various scales in various organisms, and some such as polyploidy can certainly create new plant species. However, modern biologists such as Douglas J. Futuyma conclude that essentially all claims of evolution driven by large mutations can be explained within the Darwinian evolutionary synthesis.

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