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Lamarckism (or Lamarckian inheritance) is the idea that an organism can pass on characteristics that it acquired during its lifetime to its offspring (also known as heritability of acquired characteristics or soft inheritance). It is named after the French biologist Jean-Baptiste Lamarck (1744–1829), who incorporated the action of soft inheritance into his evolutionary theories as a supplement to his concept of an inherent progressive tendency driving organisms continuously towards greater complexity, in parallel but separate lineages with no extinction. Lamarck did not originate the idea of soft inheritance, which proposes that individual efforts during the lifetime of the organisms were the main mechanism driving species to adaptation, as they supposedly would acquire adaptive changes and pass them on to offspring. When Charles Darwin published his theory of evolution by natural selection in ''On the Origin of Species'' (1859), he continued to give credence to what he called "use and disuse inheritance," but rejected other aspects of Lamarck's theories. Later, Mendelian genetics supplanted the notion of inheritance of acquired traits, eventually leading to the development of the modern evolutionary synthesis, and the general abandonment of the Lamarckian theory of evolution in biology. Despite this abandonment, interest in Lamarckism has continued as studies in the field of epigenetics have highlighted the possible inheritance of behavioral traits acquired by the previous generation. ==History== Between 1794 and 1796 Erasmus Darwin wrote ''Zoonomia'' suggesting "that all warm-blooded animals have arisen from one living filament... with the power of acquiring new parts" in response to stimuli, with each round of "improvements" being inherited by successive generations. Subsequently, Jean-Baptiste Lamarck repeated in his ''Philosophie Zoologique'' of 1809 the folk wisdom that characteristics which were "needed" were acquired (or diminished) during the lifetime of an organism then passed on to the offspring. He incorporated this mechanism into his thoughts on evolution, seeing it as resulting in the adaptation of life to local environments. Lamarck founded a school of French ''Transformationism'' which included Étienne Geoffroy Saint-Hilaire, and which corresponded with a radical British school of anatomy based in the extramural anatomy schools in Edinburgh, Scotland, which included the surgeon Robert Knox and the comparative anatomist Robert Edmond Grant. In addition, the Regius Professor of Natural History at the University of Edinburgh, Robert Jameson, was the probable author of an anonymous paper in 1826 praising "Mr. Lamarck" for explaining how the higher animals had "evolved" from the "simplest worms"—this was the first use of the word "evolved" in a modern sense. As a young student, Charles Darwin was tutored by Grant, and worked with him on marine creatures. The ''Vestiges of the Natural History of Creation'', authored by Robert Chambers in St Andrews, Scotland, and published anonymously in England in 1844, proposed a theory which combined radical phrenology with Lamarckism, causing political controversy for its radicalism and unorthodoxy, but exciting popular interest and preparing a huge and prosperous audience for Darwin. Darwin's ''On the Origin of Species'' proposed natural selection as the main mechanism for development of species, but did not rule out a variant of Lamarckism as a supplementary mechanism.〔: "But Darwin was to let go of the notion that a well-used and strengthened organ could be inherited."〕 Darwin called his Lamarckian hypothesis pangenesis, and explained it in the final chapter of his book ''The Variation of Animals and Plants under Domestication'' (1868), after describing numerous examples to demonstrate what he considered to be the inheritance of acquired characteristics. Pangenesis, which he emphasised was a hypothesis, was based on the idea that somatic cells would, in response to environmental stimulation (use and disuse), throw off 'gemmules' or 'pangenes' which travelled around the body (though not necessarily in the bloodstream). These pangenes were microscopic particles that supposedly contained information about the characteristics of their parent cell, and Darwin believed that they eventually accumulated in the germ cells where they could pass on to the next generation the newly acquired characteristics of the parents. Darwin's half-cousin, Francis Galton, carried out experiments on rabbits, with Darwin's cooperation, in which he transfused the blood of one variety of rabbit into another variety in the expectation that its offspring would show some characteristics of the first. They did not, and Galton declared that he had disproved Darwin's hypothesis of pangenesis, but Darwin objected, in a letter to the scientific journal ''Nature'', that he had done nothing of the sort, since he had never mentioned blood in his writings. He pointed out that he regarded pangenesis as occurring in Protozoa and plants, which have no blood. 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「Lamarckism」の詳細全文を読む スポンサード リンク
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