Sewall Green Wright
FRS(For) Honorary
FRSE (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 (biology), adaptation, ...
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 biolog ...
, 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 s ...
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 wor ...
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
The coefficient of inbreeding of an individual is the probability that two alleles at any locus in an individual are identical by descent from the common ancestor(s) of the two parents.
The coefficient of inbreeding is: The probability that two ...
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 using a ...
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 and o ...
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
Allele frequency, or gene frequency, is the relative frequency of an allele (variant of a gene) at a particular locus in a population, expressed as a fraction or percentage. Specifically, it is the fraction of all chromosomes in the population that ...
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 replication, DNA or viral repl ...
, migration and genetic drift. Wright also made major contributions to
mammalian and biochemical genetics.
Biography
Sewall Wright was born in
Melrose, Massachusetts 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 and o ...
. 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
Theodore Paul Wright (May 25, 1895 – August 21, 1970), also known as T. P. Wright, was a U.S. aeronautical engineer and educator.
Biography
He was born in Galesburg, Illinois on May 25, 1895. His father was the economist Philip Green Wri ...
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 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 i ...
. Wright attended Galesburg High School 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. 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.
A Doctor of Philosophy (PhD, Ph.D., or DPhil; Latin: or ') is the most common degree at the highest academic level awarded following a course of study. PhDs are awarded for programs across the whole breadth of academic fields. Because it is ...
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 i ...
. 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 high ...
, 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 university, private research university in Chicago, Illinois. Its main campus is located in Chicago's Hyde Park, Chicago, Hyde Park neighborhood. The University of Chic ...
. 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 (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 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, meetings, ...
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.
...
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-lar ...
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 and o ...
, 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 ...
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 biolog ...
. Their theoretical work is the origin of the modern evolutionary synthesis or neodarwinian synthesis. Wright was the inventor/discoverer of the inbreeding coefficient
The coefficient of inbreeding of an individual is the probability that two alleles at any locus in an individual are identical by descent from the common ancestor(s) of the two parents.
The coefficient of inbreeding is: The probability that two ...
and F-statistics
In population genetics, ''F''-statistics (also known as fixation indices) describe the statistically expected level of heterozygosity in a population; more specifically the expected degree of (usually) a reduction in heterozygosity when compared ...
, 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
Allele frequency, or gene frequency, is the relative frequency of an allele (variant of a gene) at a particular locus in a population, expressed as a fraction or percentage. Specifically, it is the fraction of all chromosomes in the population that ...
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
Allele frequency, or gene frequency, is the relative frequency of an allele (variant of a gene) at a particular locus in a population, expressed as a fraction or percentage. Specifically, it is the fraction of all chromosomes in the population that ...
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 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 ...
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 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 ...
, 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
Jay Laurence Lush (January 3, 1896 – May 22, 1982) was a pioneering animal geneticist who made important contributions to livestock breeding. He is sometimes known as the father of modern scientific animal breeding. Lush received National Me ...
, 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 Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...
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.[
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 coefficient of determination 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. He found a union of concept in Charles Hartshorne
Charles Hartshorne (; June 5, 1897 – October 9, 2000) was an American philosopher who concentrated primarily on the philosophy of religion and metaphysics, but also contributed to ornithology. He developed the neoclassical idea of God and ...
, who became a lifelong friend and philosophical collaborator. Wright endorsed a form of panpsychism. 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 s ...
that brought genetics and evolution together. Their work was essential to the contributions of Dobzhansky
Theodosius Grigorievich Dobzhansky (russian: Феодо́сий Григо́рьевич Добржа́нский; uk, Теодо́сій Григо́рович Добржа́нський; January 25, 1900 – December 18, 1975) was a prominent ...
, Mayr
Mayr is a German surname. Notable people with the surname include:
* Andrea Mayr (born 1979), Austrian female long-distance runner
* Ernst Mayr (1904–2005), German American evolutionary biologist
* Georg Mayr (1564–1623), Bavarian Jesuit pries ...
, Simpson
Simpson most often refers to:
* Simpson (name), a British surname
*''The Simpsons'', an animated American sitcom
**The Simpson family, central characters of the series ''The Simpsons''
Simpson may also refer to:
Organizations Schools
*Simpso ...
, Julian Huxley, 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 beli ...
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. Estabroo ...
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