Mutationism refers to the concept briefly held by some in the early 20th century — but now discredited — that mutations are the main mechanism of evolution.

Overview

The concept of mutationism was first proposed by the pioneer Hugo de Vries in 1900. It was particularly associated with Mendelism, which was opposed by by the biometricians led by Karl Pearson who held that natural selection was the primary cause of evolution and that large inherited characters of Mendelian genetics could not occur.

The 1920s and 1930s in the modern evolutionary synthesis, population geneticists showed that continuous variation could be caused by Mendelian inheritance and that selection could act on such characters. It was also demonstrated that levels of mutation necessary to cause significant evolution were not present in the environment and would cause sterility; e.g., in fruit flies.

Mutations however are the initial source of genetic variation, but selection and/or genetic drift must increase their frequency in a population. Mutation-selection balance acts to keep deleterious alleles out of a population.

With regard to probability, mutations are (effectively) stochastic, contrasting with natural selection a "mechanism for generating an exceedingly high degree of improbability"; i.e., non-randomness, necessary to prevent the system from falling into dissaray.

The concept of mutationism has been used by some creationists to create a straw man (or perhaps misunderstanding) of evolutionary theory, to say that the theory predicts that evolution happens only or primarily through mutations.

External links

• http://books.nap.edu/books/0309058775/html/2.html