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"Survival of the fittest" is a phrase that originated from an evolutionary theory as a way of describing the mechanism of natural selection. The biological concept of fitness is defined as reproductive success. In Darwinian terms the phrase is best understood as "Survival of the form that will leave the most copies of itself in successive generations." Herbert Spencer first used the phrase – after reading Charles Darwin's ''On the Origin of Species'' – in his ''Principles of Biology'' (1864), in which he drew parallels between his own economic theories and Darwin's biological ones, writing, "This survival of the fittest, which I have here sought to express in mechanical terms, is that which Mr. Darwin has called 'natural selection', or the preservation of favoured races in the struggle for life."〔(【引用サイトリンク】 title=Letter 5140 – Wallace, A. R. to Darwin, C. R., 2 July 1866 ) (【引用サイトリンク】 title=Letter 5145 – Darwin, C. R. to Wallace, A. R., 5 July (1866) ) ^ "Herbert Spencer in his ''Principles of Biology'' of 1864, vol. 1, p. 444, wrote: 'This survival of the fittest, which I have here sought to express in mechanical terms, is that which Mr. Darwin has called "natural selection", or the preservation of favoured races in the struggle for life.'" , citing HERBERT SPENCER, THE PRINCIPLES OF BIOLOGY 444 (Univ. Press of the Pac. 2002.)〕 Darwin responded positively to Alfred Russel Wallace's suggestion of using Spencer's new phrase "survival of the fittest" as an alternative to "natural selection", and adopted the phrase in ''The Variation of Animals and Plants under Domestication'' published in 1868.〔〔 "This preservation, during the battle for life, of varieties which possess any advantage in structure, constitution, or instinct, I have called Natural Selection; and Mr. Herbert Spencer has well expressed the same idea by the Survival of the Fittest. The term "natural selection" is in some respects a bad one, as it seems to imply conscious choice; but this will be disregarded after a little familiarity." 〕 In ''On the Origin of Species'', he introduced the phrase in the fifth edition published in 1869,〔"This preservation of favourable variations, and the destruction of injurious variations, I call Natural Selection, or the Survival of the Fittest." – 〕 intending it to mean "better designed for an immediate, local environment".〔〔"Evolutionary biologists customarily employ the metaphor 'survival of the fittest,' which has a precise meaning in the context of mathematical population genetics, as a shorthand expression when describing evolutionary processes." 〕 ==Interpreted as denoting a mechanism== The phrase "survival of the fittest" is not generally used by modern biologists as the term does not accurately describe the mechanism of natural selection as biologists conceive it. Natural selection is differential ''reproduction'' (not just ''survival'') and the object of scientific study is usually differential reproduction resulting from traits that have a genetic basis under the circumstances in which the organism finds itself, which is called ''fitness'', but in a technical sense which is quite different from the common meaning of the word. 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「Survival of the fittest」の詳細全文を読む スポンサード リンク
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