Information AboutMutationism |
| CATEGORIES ABOUT MUTATIONISM | |
| evolution | |
| molecular evolution | |
| evolutionary biology | |
| mutation | |
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HISTORY The concept of mutationism was first proposed by the pioneer geneticist Hugo De Vries in 1901 . It was particularly associated with Mendelism as championed by William Bateson , which was opposed by the biometricians led by Karl Pearson who held that Natural Selection was the primary cause of Evolution and that most variation in organisms was continuous rather than discontinuous as early forms of Mendelian Genetics emphasized. This particular form of mutationism adopted by de Vries is often called Macromutation Theory , where suddenly, large mutations could change radically a species into another (also known as a form of Saltationism ). G. Udny Yule pointed out during this debate that if most traits were thought to have multiple Mendelian characters, then the results would look continuous as well; despite this, the Mendelian-versus-biometrician controversy continued for some time. In the 1930s, though, R. A. Fisher produced a complex statistical account for how Mendelian evolution could occur, ushering in the beginnings of what would become in the 1920s and 1930s the Modern Evolutionary Synthesis . Additionally, work by Thomas Hunt Morgan resulted in what is now know as Classical Genetics , integrating Mendelism with chromosome theory and providing rigorous biological support for it as the mechanism of heredity. During the formulation of the 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 . Also, change of allele frequency powered by mutations was shown mathematically to be much lower than changes due to Natural Selection or Genetic Drift . According to this theory, however, Mutations are the initial source of Genetic Variation , but Selection and/or Genetic Drift must increase their frequency in 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. In the 1950s and 1960s , Selectionism , the idea that natural selection is the most important mechanism of evolution wasn't contested by most Evolutionary Biologists and nearly everything was thought to be the result of some form of Natural Selection (Dobzhansky, 1951). However, with the arrival of Molecular Biology , some scientists proposed that Mutational Pressure was the basic process of Evolution (Sueoka, 1962; Nei, 1983, 2005). This view is sometime called "neomutationism". NEOMUTATIONISM VS. SELECTIONISM The differences between neomutationism, was an Adaption to harsh conditions, either high Temperature (Argos ''et al.'', 1979; disproved by Galtier and Lobry, 1997) or UV Radiation (Singer and Ames, 1970). While mutationists believe it is mostly the consequence of a mutational biais, called the GC mutational pressure (Sueoka, 1964; Muto and Osawa, 1987; Gu ''et al.'', 1998). RELATION WITH CREATIONISM 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. However, neither Mutationism nor the Modern Evolutionary Synthesis takes a view that equates evolution with mutation. REFERENCES EXTERNAL LINKS
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