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Sewall Green Wright FRS(For) Honorary
FRSE Fellowship of the Royal Society of Edinburgh (FRSE) is an award granted to individuals that the Royal Society of Edinburgh, Scotland's national academy of science and letters, judged to be "eminently distinguished in their subject". This soci ...
(December 21, 1889March 3, 1988) was an American
geneticist A geneticist is a biologist or physician who studies genetics, the science of genes, heredity, and variation of organisms. A geneticist can be employed as a scientist or a lecturer. Geneticists may perform general research on genetic processes ...
known for his influential work on
evolutionary theory Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
and also for his work on path analysis. He was a founder of
population genetics Population genetics is a subfield of genetics that deals with genetic differences within and between populations, and is a part of evolutionary biology. Studies in this branch of biology examine such phenomena as adaptation, speciation, and po ...
alongside
Ronald Fisher Sir Ronald Aylmer Fisher (17 February 1890 – 29 July 1962) was a British polymath who was active as a mathematician, statistician, biologist, geneticist, and academic. For his work in statistics, he has been described as "a genius who ...
and
J. B. S. Haldane John Burdon Sanderson Haldane (; 5 November 18921 December 1964), nicknamed "Jack" or "JBS", was a British-Indian scientist who worked in physiology, genetics, evolutionary biology, and mathematics. With innovative use of statistics in biolo ...
, which was a major step in the development of the
modern synthesis Modern synthesis or modern evolutionary synthesis refers to several perspectives on evolutionary biology, namely: * Modern synthesis (20th century), the term coined by Julian Huxley in 1942 to denote the synthesis between Mendelian genetics and ...
combining
genetics Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinian friar work ...
with
evolution Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
. He discovered the inbreeding coefficient and methods of computing it in pedigree animals. He extended this work to
population Population typically refers to the number of people in a single area, whether it be a city or town, region, country, continent, or the world. Governments typically quantify the size of the resident population within their jurisdiction usi ...
s, computing the amount of
inbreeding Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are closely related genetically. By analogy, the term is used in human reproduction, but more commonly refers to the genetic disorders a ...
between members of populations as a result of random
genetic drift Genetic drift, also known as allelic drift or the Wright effect, is the change in the frequency of an existing gene variant (allele) in a population due to random chance. Genetic drift may cause gene variants to disappear completely and there ...
, and along with Fisher he pioneered methods for computing the distribution of gene frequencies among populations as a result of the interaction of
natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Cha ...
,
mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, m ...
, migration and genetic drift. Wright also made major contributions to
mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur ...
ian and biochemical genetics.


Biography

Sewall Wright was born in
Melrose, Massachusetts Melrose is a city located in the Greater Boston metropolitan area in Middlesex County, Massachusetts, United States. Its population, per the 2020 United States Census, is 29,817. It is a suburb located approximately seven miles north of Boston. ...
to Philip Green Wright and Elizabeth Quincy Sewall Wright. His parents were first cousins, an interesting fact in light of Wright's later research on
inbreeding Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are closely related genetically. By analogy, the term is used in human reproduction, but more commonly refers to the genetic disorders a ...
. The family moved three years later after Philip accepted a teaching job at
Lombard College Lombard College was a Universalist college located in Galesburg, Illinois. History Lombard College was founded in 1853 by the Universalist Church as the Illinois Liberal Institute. In 1855, however, a major fire damaged much of the college, p ...
, a Universalist 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 student
Carl Sandburg Carl August Sandburg (January 6, 1878 – July 22, 1967) was an American poet, biographer, journalist, and editor. He won three Pulitzer Prizes: two for his poetry and one for his biography of Abraham Lincoln. During his lifetime, Sandburg ...
. At the age of seven, in 1897, he wrote his first "book", entitled ''Wonders of Nature'', and he published his last paper in 1988: 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:
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 engineer Aerospace engineering is the primary field of engineering concerned with the development of aircraft and spacecraft. It has two major and overlapping branches: aeronautical engineering and astronautical engineering. Avionics engineering is sim ...
Theodore Paul Wright and the
political scientist Political science is the scientific study of politics. It is a social science dealing with systems of governance and power, and the analysis of political activities, political thought, political behavior, and associated constitutions and la ...
Quincy Wright Philip Quincy Wright (December 28, 1890 – October 17, 1970) was an American political scientist based at the University of Chicago known for his pioneering work and expertise in international law, international relations, and security studies. ...
. From an early age Wright had a love and talent for
mathematics Mathematics is an area of knowledge that includes the topics of numbers, formulas and related structures, shapes and the spaces in which they are contained, and quantities and their changes. These topics are represented in modern mathematics ...
and
biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary ...
. Wright attended
Galesburg High School Galesburg High School is a public high school in Galesburg, Illinois. Galesburg High School was established in 1861 in downtown Galesburg. It has since moved to Fremont Street on the west side of town. The school is located on of land with a full ...
and graduated in 1906. He then enrolled in
Lombard College Lombard College was a Universalist college located in Galesburg, Illinois. History Lombard College was founded in 1853 by the Universalist Church as the Illinois Liberal Institute. In 1855, however, a major fire damaged much of the college, p ...
where his father taught, to study
mathematics Mathematics is an area of knowledge that includes the topics of numbers, formulas and related structures, shapes and the spaces in which they are contained, and quantities and their changes. These topics are represented in modern mathematics ...
. He was influenced greatly by Professor
Wilhelmine Key Wilhelmine "Minnie" Marie Enteman Key (February 22, 1872 – January 31, 1955) was an American geneticist. She was the first woman to gain a PhD in zoology from the University of Chicago, where she studied coloration in paper wasps. She contrib ...
, one of the first women to receive a Ph.D. in
biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary ...
. Wright received his Ph.D. from
Harvard University Harvard University is a private Ivy League research university in Cambridge, Massachusetts. Founded in 1636 as Harvard College and named for its first benefactor, the Puritan clergyman John Harvard, it is the oldest institution of highe ...
, where he worked at the
Bussey Institute The Bussey Institute (1883–1936) was a respected biological institute at Harvard University. It was named for Benjamin Bussey, who, in 1835, endowed the establishment of an undergraduate school of agriculture and horticulture and donated land i ...
with the pioneering mammalian geneticist
William Ernest Castle William Ernest Castle (October 25, 1867 – June 3, 1962) was an early American geneticist. Early years William Ernest Castle was born on a farm in Ohio and took an early interest in natural history. He graduated in 1889 from Denison University ...
investigating the inheritance of coat colors in
mammals Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur o ...
. He worked for the
U.S. Department of Agriculture The United States Department of Agriculture (USDA) is the federal executive department responsible for developing and executing federal laws related to farming, forestry, rural economic development, and food. It aims to meet the needs of comme ...
until 1925, when he joined the Department of Zoology at the
University of Chicago The University of Chicago (UChicago, Chicago, U of C, or UChi) is a private research university in Chicago, Illinois. Its main campus is located in Chicago's Hyde Park neighborhood. The University of Chicago is consistently ranked among the b ...
. He remained there until his retirement in 1955, when he moved to the
University of Wisconsin–Madison A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. Universities typically offer both undergraduate and postgraduate programs. In the United Stat ...
. He received many honors in his long career, including the
National Medal of Science The National Medal of Science is an honor bestowed by the President of the United States to individuals in science and engineering who have made important contributions to the advancement of knowledge in the fields of behavioral and social scienc ...
(1966), the
Balzan Prize The International Balzan Prize Foundation awards four annual monetary prizes to people or organizations who have made outstanding achievements in the fields of humanities, natural sciences, culture, as well as for endeavours for peace and the br ...
(1984), and the
Darwin Medal The Darwin Medal is one of the medals awarded by the Royal Society for "distinction in evolution, biological diversity and developmental, population and organismal biology". In 1885, International Darwin Memorial Fund was transferred to the ...
of the
Royal Society The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...
(1980). He was a member of the
National Academy of Sciences The National Academy of Sciences (NAS) is a United States nonprofit, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the Nat ...
and a
Foreign Member of the Royal Society Fellowship of the Royal Society (FRS, ForMemRS and HonFRS) is an award granted by the judges of the Royal Society of London to individuals who have made a "substantial contribution to the improvement of natural knowledge, including mathematic ...
. The
American Mathematical Society The American Mathematical Society (AMS) is an association of professional mathematicians dedicated to the interests of mathematical research and scholarship, and serves the national and international community through its publications, meeting ...
selected him as the Josiah Willards Gibbs lecturer for 1941. For his work on genetics of evolutionary processes, Wright was awarded the
Daniel Giraud Elliot Medal The Daniel Giraud Elliot Medal is awarded by the U.S. National Academy of Sciences "for meritorious work in zoology or paleontology study published in a three- to five-year period." Named after Daniel Giraud Elliot, it was first awarded in 1917. L ...
from the National Academy of Sciences in 1945. He died in
Madison, Wisconsin Madison is the county seat of Dane County and the capital city of the U.S. state of Wisconsin. As of the 2020 census the population was 269,840, making it the second-largest city in Wisconsin by population, after Milwaukee, and the 80th ...
on March 3, 1988.


Family

Wright married Louise Lane Williams (1895–1975) in 1921. They had three children: Richard, Robert, and Elizabeth. Sewall Wright worshipped as a Unitarian.


Scientific achievements and credits


Population genetics

His papers on
inbreeding Inbreeding is the production of offspring from the mating or breeding of individuals or organisms that are closely related genetically. By analogy, the term is used in human reproduction, but more commonly refers to the genetic disorders a ...
,
mating system A mating system is a way in which a group is structured in relation to sexual behaviour. The precise meaning depends upon the context. With respect to animals, the term describes which males and females mate under which circumstances. Recognised ...
s, and
genetic drift Genetic drift, also known as allelic drift or the Wright effect, is the change in the frequency of an existing gene variant (allele) in a population due to random chance. Genetic drift may cause gene variants to disappear completely and there ...
make him a principal founder of theoretical population genetics, along with
R. A. Fisher Sir Ronald Aylmer Fisher (17 February 1890 – 29 July 1962) was a British polymath who was active as a mathematician, statistician, biologist, geneticist, and academic. For his work in statistics, he has been described as "a genius who a ...
and
J. B. S. Haldane John Burdon Sanderson Haldane (; 5 November 18921 December 1964), nicknamed "Jack" or "JBS", was a British-Indian scientist who worked in physiology, genetics, evolutionary biology, and mathematics. With innovative use of statistics in biolo ...
. 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 Genetic drift, also known as allelic drift or the Wright effect, is the change in the frequency of an existing gene variant (allele) in a population due to random chance. Genetic drift may cause gene variants to disappear completely and there ...
, 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. In this work he also introduced the concept of
effective population size The effective population size (''N'e'') is a number that, in some simplified scenarios, corresponds to the number of breeding individuals in the population. More generally, ''N'e'' is the number of individuals that an idealised population w ...
. Wright was convinced that the interaction of
genetic drift Genetic drift, also known as allelic drift or the Wright effect, is the change in the frequency of an existing gene variant (allele) in a population due to random chance. Genetic drift may cause gene variants to disappear completely and there ...
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 evolutionary landscapes. On these landscapes mean population fitness was the height, plotted against horizontal axes representing the allele frequencies or the average phenotypes of the population.
Natural selection Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in the heritable traits characteristic of a population over generations. Cha ...
would lead to a population climbing the nearest peak, while
genetic drift Genetic drift, also known as allelic drift or the Wright effect, is the change in the frequency of an existing gene variant (allele) in a population due to random chance. Genetic drift may cause gene variants to disappear completely and there ...
would cause random wandering. He did not accept Fisher's genetic theory of dominance, but instead considered it to arise from biochemical considerations. Although set aside for many years, his interpretation is at the basis of modern ideas of dominance.


Evolutionary theory

Wright's explanation for
stasis Stasis (from Greek στάσις "a standing still") may refer to: * A state in stability theory, in which all forces are equal and opposing, therefore they cancel out each other * Stasis (political history), a period of civil war within an ancient ...
was that organisms come to occupy
adaptive peak Adaptation, in biology, is the process or trait by which organisms or population better match their environment Adaptation may also refer to: Arts * Adaptation (arts), a transfer of a work of art from one medium to another ** Film adaptation, a ...
s. 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 Genetic drift, also known as allelic drift or the Wright effect, is the change in the frequency of an existing gene variant (allele) in a population due to random chance. Genetic drift may cause gene variants to disappear completely and there ...
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 In population genetics, gene flow (also known as gene migration or geneflow and allele flow) is the transfer of genetic material from one population to another. If the rate of gene flow is high enough, then two populations will have equivalent a ...
between the populations, these adaptations could spread to the rest of the species. This was Wright's
shifting balance theory The shifting balance theory is a theory of evolution proposed in 1932 by Sewall Wright, suggesting that adaptive evolution may proceed most quickly when a population divides into subpopulations with restricted gene flow. The name of the theory i ...
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 Sir Ronald Aylmer Fisher (17 February 1890 – 29 July 1962) was a British polymath who was active as a mathematician, statistician, biologist, geneticist, and academic. For his work in statistics, he has been described as "a genius who a ...
, who felt that most populations in nature were too large for these effects of genetic drift to be important.


Path analysis

Wright's statistical method of path analysis, which he invented in 1921 and which was one of the first methods using a
graphical model A graphical model or probabilistic graphical model (PGM) or structured probabilistic model is a probabilistic model for which a graph expresses the conditional dependence structure between random variables. They are commonly used in probabili ...
, 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.


Plant and animal breeding

Wright strongly influenced Jay Lush, who was the most influential figure in introducing
quantitative genetics Quantitative genetics deals with phenotypes that vary continuously (such as height or mass)—as opposed to discretely identifiable phenotypes and gene-products (such as eye-colour, or the presence of a particular biochemical). Both branches u ...
into
animal Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and go through an ontogenetic stage ...
and
plant breeding Plant breeding is the science of changing the traits of plants in order to produce desired characteristics. It has been used to improve the quality of nutrition in products for humans and animals. The goals of plant breeding are to produce cr ...
. 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. He did major work on the genetics of
guinea pigs The guinea pig or domestic guinea pig (''Cavia porcellus''), also known as the cavy or domestic cavy (), is a species of rodent belonging to the genus '' Cavia'' in the family Caviidae. Breeders tend to use the word ''cavy'' to describe the a ...
, and many of his students became influential in the development of mammalian genetics. He appreciated as early as 1917 that genes acted by controlling
enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...
s. 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.


Statistics

The creation of the
statistical Statistics (from German: '' Statistik'', "description of a state, a country") is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of data. In applying statistics to a scientific, industr ...
coefficient of determination In statistics, the coefficient of determination, denoted ''R''2 or ''r''2 and pronounced "R squared", is the proportion of the variation in the dependent variable that is predictable from the independent variable(s). It is a statistic used i ...
has been attributed to Sewall Wright and was first published in 1921. This metric is commonly employed to evaluate regression analyses in
computational statistics Computational statistics, or statistical computing, is the bond between statistics and computer science. It means statistical methods that are enabled by using computational methods. It is the area of computational science (or scientific computin ...
and
machine learning Machine learning (ML) is a field of inquiry devoted to understanding and building methods that 'learn', that is, methods that leverage data to improve performance on some set of tasks. It is seen as a part of artificial intelligence. Machine ...
.


Wright and philosophy

Wright was one of the few geneticists of his time to venture into
philosophy Philosophy (from , ) is the systematized study of general and fundamental questions, such as those about existence, reason, knowledge, values, mind, and language. Such questions are often posed as problems to be studied or resolved. ...
. He found a union of concept in Charles Hartshorne, who became a lifelong friend and philosophical collaborator. Wright endorsed a form of
panpsychism In the philosophy of mind, panpsychism () is the view that the mind or a mindlike aspect is a fundamental and ubiquitous feature of reality. It is also described as a theory that "the mind is a fundamental feature of the world which exists thro ...
. 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.


Legacy

Wright and Fisher, along with J.B.S. Haldane, were the key figures in the
modern synthesis Modern synthesis or modern evolutionary synthesis refers to several perspectives on evolutionary biology, namely: * Modern synthesis (20th century), the term coined by Julian Huxley in 1942 to denote the synthesis between Mendelian genetics and ...
that brought genetics and evolution together. Their work was essential to the contributions of Dobzhansky, Mayr, Simpson,
Julian Huxley Sir Julian Sorell Huxley (22 June 1887 – 14 February 1975) was an English evolutionary biologist, eugenicist, and internationalist. He was a proponent of natural selection, and a leading figure in the mid-twentieth century modern synthesis. ...
, and Stebbins. The modern 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.
Judea Pearl Judea Pearl (born September 4, 1936) is an Israeli-American computer scientist and philosopher, best known for championing the probabilistic approach to artificial intelligence and the development of Bayesian networks (see the article on belief ...
and Dana Mackenzie's ''The 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).
OpenMx OpenMx is an open source program for extended structural equation modeling. It runs as a package under R. Cross platform, it runs under Linux, Mac OS and Windows.S. Boker, M. Neale, H. Maes, M. Wilde, M. Spiegel, T. Brick, J. Spies, R. Estabrook, ...
has as its icon a representation of Wright's Piebald
Guinea Pig The guinea pig or domestic guinea pig (''Cavia porcellus''), also known as the cavy or domestic cavy (), is a species of rodent belonging to the genus '' Cavia'' in the family Caviidae. Breeders tend to use the word ''cavy'' to describe the ...
.


Bibliography

* ** vol. 1, Genetic & Biometric Foundations. ** vol. 2, Theory of Gene Frequencies. ** vol. 3, Experimental Results and Evolutionary Deductions. ** vol. 4, Variability within and Among Natural Populations.


References


Further reading

* Ghiselin, Michael T. (1997
''Metaphysics and the Origin of Species''
NY: SUNY Press. * * * Wright 1934
"The Method of Path Coefficients"
''Annals of Mathematical Statistics'', 5: 161-215 * * Wright 1983
"Path Analysis in Genetic Epidemiology: A Critique"


External links



by Edric Lescouflair and James F. Crow
Sewall Wright Papers
at the
American Philosophical Society The American Philosophical Society (APS), founded in 1743 in Philadelphia, is a scholarly organization that promotes knowledge in the sciences and humanities through research, professional meetings, publications, library resources, and communit ...
* {{DEFAULTSORT:Wright, Sewall Green 1889 births 1988 deaths American biologists American statisticians American Unitarians Evolutionary biologists Fellows of the Econometric Society Foreign Members of the Royal Society Bussey Institution alumni History of genetics Lombard College alumni Members of the United States National Academy of Sciences Modern synthesis (20th century) National Medal of Science laureates Panpsychism Population geneticists 20th-century biologists