EVOGENIO® - Evolutionäre Kunst

- Sewall Wright


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Sewall [Green] Wright (* 21. Dezember 1889 in Melrose (Massachusetts); † 3. März 1988) war ein amerikanischer Genetiker, der zusammen mit Ronald Fisher und John Burdon Sanderson Haldane die Populationsgenetik entwickelte, die zur Synthetischen Evolutionstheorie führte. Er trug Wesentliches zur Theorie der genetischen Drift bei (auch bekannt als ‚Sewall Wright Effekt'). Er entwickelte den Inzuchtkoeffizienten und beschrieb viele seiner Anwendungen. Wright entwickelte die „Fitness-Landschaften“ und betonte die Bedeutung der Wechselwirkung von genetischer Drift und von natürlicher Selektion für die Evolution. Er übertrug die natürliche Selektion auf die Tier- und Pflanzenzucht. Seine Arbeit auf dem Gebiet der Populationsgenetik beeinflusste wesentlich Jay Lush, der bahnbrechende Arbeiten in quantitativer Genetik für die Tier- und Pfanzenzucht lieferte.

Leben 

Sewall Green Wright wurde am 21. Dezember 1889 in Melrose (Massachusetts) geboren. Seine Eltern Philip Green Wright und Elisabeth Quincy Sewall Wright zogen nach Galesburg (Illinois), wo sein Vater eine Lehrerstelle am College annahm. Er hatte zwei Brüder, Quincy und Theodore Paul. Er erwarb seinen B.S. am Lombard College 1911, seinen M.S. an der University of Illinois 1912.

1915 erreichte er seinen Doktortitel an der Harvard Universität; seine Dissertation über die Fellfarben bei Meerschweinchen trägt den Titel An Intensive Study of the Inheritance of Color and of Other Coat Characteristics in Guinea Pigs. Wright führte ausgedehnte Zuchtversuche mit Meerschweinchen durch und fand 1917, dass die Gene die Herstellung von Enzymen steuerten. Sewall heiratete 1921 Louise Williams, eine Lehrerin für Genetik 1921. Die beiden hatten drei Kinder Elizabeth Rose, Richard und Robert.

Seine berufliche Laufbahn verbrachte er zunächst am United States Department of Agriculture (USDA) in Washington D. C. 1915 - 1925, wo es seine Aufgabe war, die Qualität des Viehbestands zu verbessern.

1926 wechselte er als Professor an die University of Chicago und blieb dort, bis er 1955 mit 65 Jahren pensioniert wurde.

Wright erfand die 'Adaptive Landschaften', Fitness-Landschaften. Man kann sich die unterschiedliche Fitness (Reproduktionserfolg) von unterschiedlichen Gen-Kombinationen als eine hügelige Landschaft vorstellen. Täler in dieser Landschaft bedeuten geringeren Reproduktionserfolg der Gen-Kombinationen, Hügel repräsentieren günstigere Gen-Kombinationen. Die natürliche Auslese verschiebt die Populationen auf die Gipfel der Hügel. Aber da die Umwelt sich dauernd ändert, verschieben sich die Gipfel und die Populationen folgen ihnen in einer nie endenden Reise.

Wright führte auch die shifting balance theory ein: Eine große Population aufgeteilt in kleinere Gruppen hat die besten Chancen, die Umgebung zu erforschen und die höchsten Fitness-Gipfel in der Fitnesslandschaft zu finden. Durch die Aufteilung in kleinere Gruppen werden die genetische Drift und Gründereffekte verstärkt und die Erkundung benachbarter Fitnessgipfel ermöglicht. Wright drückte seine Gedanken in schwierigen mathematischen Formeln aus, welche zu Missverständnissen führten. Über seine shifting balance theory kam es zu erbitterten Auseinandersetzung mit Ronald Fisher. Wright war scheu und bescheiden, aber hart in akademischen Fragen.

Wright wechselte als emeritierter Professor zur Universität von Wisconsin, welche ein Pensionsalter von 70 Jahren hatte, und arbeitete dort weitere 5 Jahre von 1955 bis 1960. Auch nach seiner zweiten Pensionierung blieb er aktiv. Er verfasste sein vierbändiges Werk Evolution and the Genetics of Populations 1988. Viele seiner Doktoranden lieferten wichtige Beiträge zur Entwicklung der Säugetiergenetik.

Sewall Wright starb am 3. März 1988 im Alter von 98 Jahren.


Ehrungen 

1950 bekam er den John Frederick Lewis Award von der American Philosophical Society[1]. Wright wurde 1963 als „Foreign Member“ in die Royal Society gewählt, die ihm 1980 die Darwin-Medaille verlieh. Er erhielt 10 Ehrendoktortitel. Weitere Auszeichnungen:


Werke 


Literatur 


Siehe auch 


Einzelreferenzen

  1. ↑ John Frederick Lewis Award: Auszeichnungen.



Quelle (05.2008): http://de.wikipedia.org/wiki/Sewall_Wright






Sewall Green Wright (December 21, 1889 – March 3, 1988) was an American geneticist known for his influential work on evolutionary theory and also for his work on path analysis. With R. A. Fisher and J.B.S. Haldane, he was a founder of theoretical population genetics. He is the discoverer of the inbreeding coefficient and of methods of computing it in pedigrees. He extended this work to populations, computing the amount of inbreeding of members of populations as a result of random genetic drift, and he and Fisher pioneered methods for computing the distribution of gene frequencies among populations as a result of the interaction of natural selection, mutation, migration and genetic drift. The work of Fisher, Wright, and Haldane on theoretical population genetics was a major step in the development of the modern evolutionary synthesis of genetics with evolution. Wright also made major contributions to mammalian genetics and biochemical genetics.

Biography

Sewall Wright was born in Melrose, Massachusetts to Philip Green Wright and Elizabeth Quincy Sewall Wright. The family moved three years later after Philip accepted a teaching job at Lombard College, a Universalist college in Galesburg, Illinois.

He was the youngest of three gifted brothers – the others being the aeronautical engineer Theodore Paul Wright and the political scientist Quincy Wright. From an early age Wright had a love and talent for mathematics and biology. Wright attended Galesburg High School and graduated in 1906. He then enrolled in Lombard College where his father taught, to study mathematics. He was influenced greatly by Professor Wilhelmine Entemann Key, one of the first women to receive a Ph.D. in biology. Wright received his Ph.D. from Harvard University, where he worked with the pioneering mammalian geneticist William Ernest Castle investigating the inheritance of coat colors in mammals. He worked for the U.S. Department of Agriculture until 1925, when he joined the Department of Zoology at the University of Chicago. He remained there until his retirement in 1955, when he moved to the University of Wisconsin-Madison. He received many honors in his long career, including the National Medal of Science, the Balzan Prize, and the Darwin Medal of the Royal Society. He was a member of the National Academy of Science and a Foreign Member of the Royal Society.

Wright married Louise Lane Williams (1895-1975) in 1921. They had three children: Richard, Robert, and Elizabeth.


Scientific achievements and credits

His papers on inbreeding, mating systems, and genetic drift make him a principal founder of theoretical population genetics, along with R. A. Fisher and J. B. S. Haldane. Their theoretical work is the origin of the modern evolutionary synthesis or neodarwinian synthesis. Wright was the inventor/discoverer of the inbreeding coefficient and F-statistics, standard tools in population genetics. He was the chief developer of the mathematical theory of genetic drift, which is sometimes known as the Sewall Wright effect, cumulative stochastic changes in gene frequencies that arise from random births, deaths, and Mendelian segregations in reproduction. Wright was convinced that the interaction of genetic drift and the other evolutionary forces was important in the process of adaptation. He described the relationship between genotype or phenotype and fitness as fitness surfaces or fitness landscapes. On these landscapes fitness was the height, plotted against horizontal axes representing the allele frequencies or the average phenotypes of the population. Natural selection would lead to a population climbing the nearest peak, while genetic drift would cause random wandering.

Wright's explanation for stasis was that organisms come to occupy adaptive peaks. In order to evolve to another, higher peak, the species would first have to pass through a valley of maladaptive intermediate stages. This could happen by genetic drift if the population is small enough. If a species was divided into small populations, some could find higher peaks. If there was some gene flow between the populations, these adaptations could spread to the rest of the species. This was Wright's shifting balance theory of evolution. There has been much skepticism among evolutionary biologists as to whether these rather delicate conditions hold often in natural populations. Wright had a long standing and bitter debate about this with R. A. Fisher, who felt that most populations in nature were too large for these effects of genetic drift to be important.

Wright strongly influenced Jay Lush, who was the most influential figure in introducing quantitative genetics into animal and plant breeding. Wright's statistical method of path analysis, which he invented in 1921 and which was one of the first methods using a graphical model, is still widely used in social science. He was a hugely influential reviewer of manuscripts, as one of the most frequent reviewers for Genetics. Such was his reputation that he was often credited with reviews that he did not write.

He did major work on the genetics of guinea pigs, and many of his students became influential in the development of mammalian genetics. He appreciated as early as 1917 that genes acted by controlling enzymes.


Wright and philosophy

Wright was one of the few geneticists of his time to venture into philosophy. He found a union of concept in Charles Hartshorne, who became a lifelong friend and philosophical collaborator. Wright believed that the birth of the consciousness was not due to a mysterious property of increasing complexity, but rather an inherent property, therefore implying these properties were in the most elementary particles.


Legacy

Wright and Fisher were the key figures in the neodarwinian synthesis that brought genetics and evolution together. Their work was essential to the contributions of Dobzhansky, Mayr, Simpson, Julian Huxley, and Stebbins. The neodarwinian synthesis was the most important development in evolutionary biology after Darwin. Wright also had a major effect on the development of mammalian genetics and biochemical genetics.


Trivia

Since Wright developed the methods used for assessing the degree of inbreeding and its effects, it is notable that his own parents were first cousins. As a child he helped his father and brother print and publish an early book of poems by his father's student Carl Sandburg.


References


Bibliography


Books by Wright



External links




Quelle (05.2008): http://en.wikipedia.org/wiki/Sewall_Wright




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