Psychology Dictionary of ArgumentsHome
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| Variation: Variation in evolution refers to the differences in traits among individuals of a population. These variations can be caused by genetic factors, environmental factors, or a combination of both. Variation is essential for evolution because it provides the raw material for natural selection to act upon. See also Evolution, Mutation, Selection, Darwinism._____________Annotation: The above characterizations of concepts are neither definitions nor exhausting presentations of problems related to them. Instead, they are intended to give a short introduction to the contributions below. – Lexicon of Arguments. | |||
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Nikolai I. Vavilov on Variation - Dictionary of Arguments
Gould II 132ff Variation/Evolution/Vavilov/Gould: Nikolai I. Vavilov was the leading Mendelian geneticist in Russia. In 1936, he served as the main target for the Soviet agronomist T. D. Lyssenko, who had a great influence under Stalin. Vavilov was attacked because of his theory, the so-called law of homologues rows in variation. Vavilov had collected barley, oats and millet from a wide variety of different breeds of wheat from various locations, and noted that within the different species of a genus, but also frequently within the species of related groups, remarkably similar series of varieties could be found. II 135 Definition homologous: similar due to inheritance of the same genes, Definition analogous: similar due to forced adaptation to the environment. Vavilov thesis: The new species emerge by developing genetic differences that exclude crossbreeding with related species. But the new species is not all genetically different from its ancestors. Most of them remain untouched. The parallel variations thus represent the "play through" of the same genetic abilities, which are inherited as blocks of one species to another. Gould: Darwin does not disagree with such a thesis, since it gives the selection an important role. While each variety can represent a predictable latent ability, its development in any climate or geographic region requires selection to maintain the adaptive variant and eliminate others. DarwinismVsVavilov: However, Vavilov's thesis comes into conflict with strict Darwinism, since it weakens the main doctrine that selection is the creating force of evolution. >Evolution, >Darwinism, >Ch. Darwin. II 136 Random and undirected variation plays a major role in Darwin because it determines the central position of selection by guaranteeing that the evolutionary variation itself cannot be attributed to variation. >Mutation. The variation is only the raw material. It arises in all directions and is at least not arranged preferably in an adaptive way. The direction is slowly being determined by natural selection, as the more adapted generations proliferate. However, if the possibilities are very limited and one species shows all of its different varieties, then this choice cannot be explained by selection alone. That's how Vavilov sets himself apart from Darwin. VavilovVsDarwin: Variation does not take place in all directions, but in classes that are analogous to those of chemistry and crystallography. GoudlVsVavilov: Vavilov underemphazised the creative role of the environment. II 139 Lysenko/Gould: Lysenko was a charlatan and undialectic (against his own assertion) by considering plants as modelling clay in the hands of the forming environment. Vavilov died in the name of an apparant Lamarckism. There was an excessively strict Darwinism in the Soviet Union, which misinterpreted Darwin. >Lamarckism. II 140 Gould: From today's perspective, Vavilov has cast a glimpse of something important. New species do not inherit their adult form from their ancestors. They will receive a complex genetic system and a number of development opportunities. This set of options narrows the variation width to a line along which the selection can select points that it cannot move. II 141 In recent experiments with recurring traits in bred mice one has not found Darwinian homologous series in the sense of Vavilov. The simplest and most common conclusion would be to consider snails with a smooth shell on all islands as related and those with a ribbed shell as members of another related group. However, we now know that the complex set of properties always arises independently. VsVavilov: he has overemphasized the internal limitations and reduced the power of selection too much. >Selection._____________Explanation of symbols: Roman numerals indicate the source, arabic numerals indicate the page number. The corresponding books are indicated on the right hand side. ((s)…): Comment by the sender of the contribution. Translations: Dictionary of Arguments The note [Concept/Author], [Author1]Vs[Author2] or [Author]Vs[term] resp. "problem:"/"solution:", "old:"/"new:" and "thesis:" is an addition from the Dictionary of Arguments. If a German edition is specified, the page numbers refer to this edition. |
Vavilov I Nikolai I. Vavilov Origin and Geography of Cultivated Plants Cambridge 2009 Gould I Stephen Jay Gould The Panda’s Thumb. More Reflections in Natural History, New York 1980 German Edition: Der Daumen des Panda Frankfurt 2009 Gould II Stephen Jay Gould Hen’s Teeth and Horse’s Toes. Further Reflections in Natural History, New York 1983 German Edition: Wie das Zebra zu seinen Streifen kommt Frankfurt 1991 Gould III Stephen Jay Gould Full House. The Spread of Excellence from Plato to Darwin, New York 1996 German Edition: Illusion Fortschritt Frankfurt 2004 Gould IV Stephen Jay Gould The Flamingo’s Smile. Reflections in Natural History, New York 1985 German Edition: Das Lächeln des Flamingos Basel 1989 |
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