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Orthogenesis also known as orthogenetic evolution is an obsolete biological hypothesis that organisms have an innate tendency to evolve in a unilinear fashion due to some internal mechanism or "driving force".〔Bowler, Peter J. (1989). ''Evolution: The History of an Idea''. University of California Press. pp. 268-270. ISBN 0-520-06385-6〕〔Mayr, Ernst. (1988). ''Toward a New Philosophy of Biology: Observations of an Evolutionist''. Harvard University Press. p. 499. ISBN 0-674-89666-1〕 American paleontologist George Gaylord Simpson (1953) in an attack on orthogenesis described it as "the mysterious inner force".〔Simpson, George Gaylord. (1953). ''Life of the Past: An Introduction to Paleontology''. Yale University Press. p. 125〕 Classic proponents of orthogenesis rejected the theory of natural selection as the organizing mechanism in evolution for a rectilinear model of directed evolution. The term ''orthogenesis'' was popularized by Theodor Eimer.〔Ulett, Mark A. (2014). ''Making the case for orthogenesis: The popularization of definitely directed evolution (1890–1926)''. Studies in History and Philosophy of Biological and Biomedical Sciences 45: 124-132〕 Which the emergence of the modern evolutionary synthesis, in which the genetic mechanisms of evolution were discovered, the hypothesis of orthogenesis was refuted.〔Levinton, Jeffrey S. (2001). ''Genetics, Paleontology, and Macroevolution''. Cambridge University Press. pp. 14-16. ISBN 0-521-80317-9〕〔Montgomery, Georgina M; Largent, Mark A. (2015). ''A Companion to the History of American Science''. Wiley. p. 218. ISBN 978-1-4051-5625-7 "With the integration of Mendelian genetics and population genetics into evolutionary theory in the 1930s a new generation of biologists applied mathematical techniques to investigate how changes in the frequency of genes in populations combined with natural selection could produce species change. This demonstrated that Darwinian natural selection was the primary mechanism for evolution and that other models of evolution, such as neo-Lamarckism and orthogenesis, were invalid."〕 ==Definition== Orthogenesis was a term first used by the biologist Wilhelm Haacke in 1893.〔Gould, Stephen Jay. (2002). ''The Structure of Evolutionary Theory''. Harvard University Press. pp. 351-352. ISBN 978-0674006133〕 Theodor Eimer was the first to give the word a definition; he defined orthogenesis as "the general law according to which evolutionary development takes place in a noticeable direction, above all in specialized groups."〔Lane, David H. (1996). ''The Phenomenon of Teilhard: Prophet for a New Age''. Mercer University Press. pp. 60-64. ISBN 0-86554-498-0〕 In 1922, the zoologist Michael F. Guyer wrote: () has meant many different things to many different people, ranging from a, mystical inner perfecting principle, to merely a general trend in development due to the natural constitutional restrictions of the germinal materials, or to the physical limitations imposed by a narrow environment. In most modern statements of the theory, the idea of continuous and progressive change in one or more characters, due according to some to internal factors, according to others to external causes-evolution in a "straight line" seems to be the central idea.〔Guyer, Michael F. (1922). (''Orthogenesis and Serological Phenomena'' ). The American Naturalist. Vol. 56, No. 643. pp. 116-133.〕 Orthogenesis was often related to neo-Lamarckism; Eimer popularized the concept of orthogenesis in his book ''Organic Evolution as the Result of the Inheritance of Acquired Characteristics According to the Laws of Organic Growth'' (1890). In his work Eimer used examples such as the evolution of the horse to argue that evolution had proceeded in a regular single direction that was difficult to explain by random variation. To orthogenesis trends in evolution were often nonadaptive and in some cases species could be led to extinction.〔Sapp, Jan. (2003). ''Genesis: The Evolution of Biology''. pp. 69-70. OUP USA. ISBN 978-0195156195〕 Peter J. Bowler has defined orthogenesis as: Literally, the term means evolution in a straight line, generally assumed to be evolution that is held to a regular course by forces internal to the organism. Orthogenesis assumes that variation is not random but is directed towards fixed goals. Selection is thus powerless, and the species is carried automatically in the direction marked out by internal factors controlling variation.〔 According to (Schrepfer, 1983): Orthogenesis meant literally "straight origins", or "straight line evolution". The term varied in meaning from the overtly vitalistic and theological to the mechanical. It ranged from theories of mystical forces to mere descriptions of a general trend in development due to natural limitations of either the germinal material or the environment... By 1910, however most who subscribed to orthogenesis hypothesized some physical rather than metaphysical determinant of orderly change.〔Schrepfer, Susan R. (1983). ''Fight to Save the Redwoods: A History of the Environmental Reform, 1917-1978''. University of Wisconsin Press. pp. 81-82. ISBN 978-0299088545〕 Orthogenesis has been described as an "anti-Darwinian" evolutionary theory because of its stance on the Darwinian mechanism of natural selection.〔Bowler, Peter J. (1992). ''The Eclipse of Darwinism: Anti-Darwinian Evolution Theories in the Decades around 1900''. The Johns Hopkins University Press. pp. 141-181. ISBN 978-0801843914〕 After studying butterfly coloration Theodor Eimer published a widely read book on orthogenesis titled ''On Orthogenesis: And the Impotence of Natural Selection in Species Formation'' (1898). In the book Eimer claimed there were trends in evolution with no adaptive significance and thus would be difficult to explain by natural selection.〔Timothy Shanahan. (2004). ''The Evolution of Darwinism: Selection, Adaptation, and Progress in Evolutionary Biology''. Cambridge University Press. p. 121. ISBN 978-0521541985〕 Stephen J. Gould wrote a detailed biography of Eimer. Gould wrote that Eimer was a materialist who rejected any vitalist or teleological approach to orthogenesis and explained that Eimer's criticism of natural selection was common amongst many evolutionists of his generation as they were searching for alternative evolutionary mechanisms as it was believed at the time that natural selection could not create new species.〔Gould, Stephen Jay. (2002). ''The Structure of Evolutionary Theory''. Harvard University Press. pp. 355-364. ISBN 978-0674006133〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Orthogenesis」の詳細全文を読む スポンサード リンク
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