Sewall Wright | |
|---|---|
 Wright in 1954 | |
| Born | (1889-12-21)December 21, 1889 Melrose, Massachusetts, U.S. |
| Died | March 3, 1988(1988-03-03) (aged 98) Madison, Wisconsin, U.S. |
| Education | Lombard College (BSc) University of Illinois Urbana-Champaign (MSc) Harvard University (PhD)[2] |
| Known for | Coefficient of determination Population genetics Causal graph F-statistics Fixation index Fitness landscape Genetic rescue Genetic drift Inbreeding coefficient Path analysis Shifting balance theory Threshold model |
| Awards | Daniel Giraud Elliot Medal (1945) Weldon Memorial Prize (1947) National Medal of Science (1966) Darwin Medal (1980) Thomas Hunt Morgan Medal (1982) Balzan Prize (1984) |
| Scientific career | |
| Fields | Genetics |
| Institutions | University of Chicago[1] (1926–1954) University of Wisconsin[1] (1955–1960) |
| Doctoral advisor | William Ernest Castle |
| Other academic advisors | Wilhelmine Key |
Sewall Green WrightForMemRS[3]HonFRSE (December 21, 1889 – March 3, 1988) was an Americangeneticist known for his influential work onevolutionary theory and also for his work onpath analysis. He was a founder ofpopulation genetics alongsideRonald Fisher andJ. B. S. Haldane, which was a major step in the development of themodern synthesis combininggenetics with evolution. He discovered theinbreeding coefficient and methods of computing it inpedigree animals. He extended this work topopulations,[4] computing the amount ofinbreeding between members of populations as a result of randomgenetic drift, and along with Fisher he pioneered methods for computing the distribution ofgene frequencies among populations as a result of the interaction ofnatural selection,mutation, migration and genetic drift. Wright also made major contributions tomammalian and biochemical genetics.[5][6][7]
Sewall Wright was born inMelrose, Massachusetts, toPhilip Green Wright and Elizabeth Quincy Sewall Wright. His parents were first cousins,[8] an interesting fact in light of Wright's later research oninbreeding. The family moved three years later after Philip accepted a teaching job atLombard College, aUniversalist college in Galesburg, Illinois.
As a child, Wright helped his father and brother print and publish an early book of poems by his father's studentCarl Sandburg. At the age of seven, in 1897, he wrote his first "book", entitledWonders of Nature,[5] and he published his last paper in 1988:[9] he can be claimed, therefore, to be the scientist with the longest career of science writing. Wright's astonishing maturity at the age of seven may be judged from the following excerpt quoted in the obituary:[5]
Have you ever examined the gizzard of a fowl? The gizzard of a fowl is a deep red colar with blu at the top. First on the outside is a very thick muscle. Under this is a white and fleecy layer. Holding very tight to the other. I expect you know that chickens eat sand. The next two layers are rough and rumply. These layers hold the sand. They grind the food. One night when we had company we had chicken-pie. Our Aunt Polly cut open the gizzard, and in it we found a lot of grain, and some corn.
He was the oldest of three gifted brothers—the others being the aeronautical engineerTheodore Paul Wright and the political scientistQuincy Wright. From an early age Wright had a love and talent for mathematics and biology. Wright attendedGalesburg High School and graduated in 1906. He then enrolled inLombard College where his father taught, to study mathematics. He was influenced greatly by ProfessorWilhelmine Key, one of the first women to receive a Ph.D. in biology.[10][11][12] Wright received his Ph.D. fromHarvard University, where he worked at theBussey Institute with the pioneering mammalian geneticistWilliam Ernest Castle investigating the inheritance of coat colors in mammals. He worked for theU.S. Department of Agriculture until 1925, when he joined the Department of Zoology at theUniversity of Chicago. He remained there until his retirement in 1955, when he moved to theUniversity of Wisconsin–Madison. He received many honors in his long career, including theNational Medal of Science (1966), theBalzan Prize (1984), and theDarwin Medal of theRoyal Society (1980). He was a member of theNational Academy of Sciences,[13] theAmerican Philosophical Society,[14] theAmerican Academy of Arts and Sciences,[15] and aForeign Member of the Royal Society.[3] TheAmerican Mathematical Society selected him as the Josiah Willards Gibbs lecturer for 1941.[16][17] For his work on genetics of evolutionary processes, Wright was awarded theDaniel Giraud Elliot Medal from the National Academy of Sciences in 1945.[18]
He died inMadison, Wisconsin, on March 3, 1988.
Wright married Louise Lane Williams (1895–1975) in 1921.[19][20] They had three children: Richard, Robert, and Elizabeth.[21][22]
Sewall Wright worshipped as aUnitarian.[23][24]
His papers oninbreeding,[4][25]mating systems,[26] andgenetic drift[27] make him a principal founder oftheoretical population genetics, along withR. A. Fisher andJ. B. S. Haldane. Their theoretical work is the origin of themodern evolutionary synthesis or neo-Darwinian synthesis.[28] Wright was the inventor/discoverer of theinbreeding coefficient andF-statistics, standard tools in population genetics. He was the chief developer of the mathematical theory of genetic drift,[27] which is sometimes known as the Sewall Wright effect,[29] cumulative stochastic changes ingene frequencies that arise from random births, deaths, and Mendelian segregations in reproduction. In this work he also introduced the concept ofeffective population size. 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 andfitness asfitness surfaces orevolutionary landscapes. On these landscapes mean population fitness was the height, plotted against horizontal axes representing theallele 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. He did not accept Fisher's genetic theory of dominance,[30] but instead considered it to arise from biochemical considerations.[31][32] Although set aside for many years, his interpretation is at the basis of modern ideas of dominance.[33][34]
Wright's explanation forstasis was that organisms come to occupyadaptive peaks.[35] 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[27] if the population is small enough. If a species was divided into small populations, some could find higher peaks. If there was somegene flow between the populations, these adaptations could spread to the rest of the species. This was Wright'sshifting 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's statistical method ofpath analysis,[4][36] which he invented in 1921 and which was one of the first methods using agraphical model, is still widely used in social science. He was a hugely influential reviewer of manuscripts,[3] as one of the most frequent reviewers forGenetics.
Wright strongly influencedJay Lush, who was the most influential figure in introducingquantitative genetics into animal and plant breeding. From 1915 to 1925 Wright was employed by the Animal Husbandry Division of the U.S. Bureau of Animal Husbandry. His main project was to investigate the inbreeding that had occurred in the artificial selection that resulted in the leading breeds of livestock used in American beef production. He also performed experiments with 80,000 guinea pigs in the study of physiological genetics. Furthermore he analyzed characters of some 40,000 guinea pigs in 23 strains of brother-sister matings against a random-bred stock. (Wright 1922a-c). The concentrated study of these two groups of mammals eventually led to the Shifting Balance Theory and the concept of "surfaces of selective value" in 1932.[9]
He did major work on the genetics of guinea pigs,[37][38] and many of his students became influential in the development of mammalian genetics. He appreciated as early as 1917 that genes acted by controllingenzymes. An anecdote about Wright, disclaimed by Wright himself, describes a lecture during which Wright tucked an unruly guinea pig under his armpit, where he usually held a chalkboard eraser: according to the anecdote, at the conclusion of the lecture, Wright absent-mindedly began to erase the blackboard using the guinea pig.[citation needed]
The creation of thestatisticalcoefficient of determination has been attributed to Sewall Wright and was first published in 1921.[39]This metric is commonly employed to evaluateregression analyses incomputational statistics andmachine learning.
Wright was one of the few geneticists of his time to venture intophilosophy. He found a union of concept inCharles Hartshorne, who became a lifelong friend and philosophical collaborator. Wright endorsed a form ofpanpsychism. He 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.[40]
Wright and Fisher, along with J.B.S. Haldane, were the key figures in themodern synthesis that brought genetics and evolution together. Their work was essential to the contributions ofDobzhansky,Mayr,Simpson,Julian Huxley, andStebbins. The modern synthesis was the most important development in evolutionary biology afterDarwin. Wright also had a major effect on the development of mammalian genetics and biochemical genetics.
Judea Pearl and Dana Mackenzie'sThe Book of Why (2018) describes the contribution of Wright's work on path analysis and delays in its acceptance by several technical disciplines (specifically statistics and formal causal analysis).[41]
OpenMx has as its icon a representation of Wright's piebaldguinea pig.
They were married in Granville on September 10, 1921... The Wrights had two boys, Richard and Robert, during the remaining four years in Washington.
Wright worshipped as a Unitarian
Unitarian.
