Wright, Sewall, 1889-1988

Alternative names
Birth 1889-12-21
Death 1988-03-03

Biographical notes:

Sewall Wright was a geneticist and educator, and was elected to the American Philosophical Society in 1932.

From the description of Papers, ca. 1915-1985. (American Philosophical Society Library). WorldCat record id: 122489532

One of the pioneers of quantitative genetics and evolutionary biology, Sewall Wright was born in Melrose, Massachusetts, to Philip Green Wright and Elizabeth Quincy Sewall Wright on December 21, 1889. He was, as he was fond of noting, the child of two cousins - the result of inbreeding. From early in his career, Wright contributed to emerging understandings of Darwinian natural selection and Mendelian genetics to lay the groundwork for modern population genetics and the Neo-Darwinian "modern synthesis." He made profound theoretical contributions in the theories of genetic drift and shifting balance, and was equally important in analyzing problems in the relationship of genotype and phenotype, biometrics, and biostatistics.

The hallmark of Wright's scientific work was his ability to combine experimental and theoretical approaches, and to apply novel mathematical and statistical methods to analyze problems in biology. Many of his theoretical insights took years to prove empirically, and others were so computationally intensive that they could not easily be tackled in the pre-computer era, but his influence, along with that of his friend, J.B.S. Haldane, and some-time antagonist, R. A. Fisher, helped reorient the disciplines of evolutionary biology and genetics along more rigorous, quantitive lines.

Wright's professional education began at Lombard College (BS, 1911), now defunct, and the University of Illinois (MS, 1912), from which he gained admission to Harvard. Opting to work on guinea pigs, one of the first groups of animals to be thoroughly studied by geneticists, Wright received his doctorate of science in 1915 for the lucidly-titled dissertation, An Intensive Study of the Inheritance of Color and of Other Coat Characteristics in Guinea Pigs . His choice of topic proved particularly fruitful in landing his first professional position, as Senior Animal Husbandman with the U.S. Department of Agriculture.

The U.S.D.A. was interested in having the brilliant young geneticist begin to analyze the extensive set of trait records they had gathered for their inbred guinea pig colonies established in 1906, all in the hope of applying the findings to improve livestock breeding. To make the connections between guinea pigs and swine, Wright felt it necessary first to develop a general theory of population genetics, which in turn, he argued, required more powerful and flexible statistical techniques than had previously been used. By 1918, Wright had worked out a new statistical approach, path analysis, which now has wide application in sociology, econometrics, and behavioral genetics, and with this new tool, began investigating some fundamental questions in inheritance and population genetics, delving into the relative influence of heredity and the environment in determining the appearance of traits.

By the early 1920s, Wright's methodological and theoretical approaches had matured, and he later believed that by the time he left the U.S.D.A. for the University of Chicago in 1926, he had developed most of his fundamental ideas about evolutionary processes. His first theoretical paper, the influential "Evolution in Mendelian populations," was written in 1925, though not published until 1931. Among the most controversial and far-reaching of his ideas was the theory of genetic drift, which was as widely misunderstood and misrepresented, according to Wright, as it was widely known, and which was the crux of a long-standing argument in the literature with R.A. Fisher, among others. Based on his findings, Wright suggested that small, random genetic changes ("drift") in small local populations can greatly increase the "field of variability" available for natural selection. The implications for understanding the speciation process and the rates and trajectories of evolutionary change were profound, and although controversial, his theory had a galvanizing influence on evolutionary studies, expanding the range of potential evolutionary mechanisms and invigorating debate over evolutionary mechanics. Although Wright is often said to have presented a "non-Darwinian" model for evolutionary change, he later insisted that what he had provided was instead a means of producing variability upon which the powerful forces of Darwinian natural selection could operate.

At the U.S.D.A. and at the University of Chicago, Wright also began to develop a view of evolution as consisting largely of "occasional shifts" from one state of genetic near equilibrium to another, rather than the progressivist paradigm that had dominated evolutionary studies (maintaining that evolution proceeded by the slow, incremental accumulation of small mutations and concentrating on the fixation of discrete characters). Perhaps more subtly, Wright also insisted upon focussing upon the evolution of "interaction systems" as opposed to isolated traits or organisms in isolation of their populations, laying the groundwork for understanding the evolutionary process as occurring at more than one hierarchically related levels. "An organism," he wrote, "is not a mere aggregation of characters, but a harmonious, tightly integrated entity," implying that this integration was as true at the level of the population as the gene. It would not be overstatement to suggest that Wright's theoretical, statistical, and empirical studies, in interaction with the work of Fisher, Haldane, George Gaylord Simpson, and others, were instrumental in fashioning the Neo-Darwinian synthesis of the 1940s, representing the firm fusion of Mendelian and Darwinian principles, and in galvanizing the macroevolutionary studies of the 1970s and 1980s.

At Chicago, Wright was employed (successively) as Associate Professor of Zoology, Professor, and the Ernest D. Burton Distinguished Service Professor, earning a reputation as a conscientious, demanding, and engaging teacher, who always incorporated the latest available information in his lectures. He also spent visiting years as Hitchcock Professor at the University of California Berkeley (1943) and as Fulbright Professor at the University of Edinburgh (1949-1950).

In 1955, Wright joined the faculty of the University of Wisconsin as Leon J. Cole Professor of Genetics, and worked for five years until his "retirement" in 1960. For Wright, though, retirement did not mean a slacking off of research. Virtually until the day of his death at age 98, Wright remained an active participant in the Genetics Department at Wisconsin as Professor Emeritus. Many of the 210 scientific papers he wrote during his career were published after his departure from Chicago -- literally up until the time of his death -- and his magnum opus, the four volume Evolution and the Genetics of Populations (Chicago, 1968-1978), was completed only months before his 90th birthday.

Wright's professional associations were numerous, as were the laurels of his innovative and influential scientific career. He was awarded ten honorary doctorates during his lifetime, was president of five scientific organizations and the recipient of nine medals or prizes, and he held memberships in thirteen scientific societies or national and international organizations. In 1932, he was elected to membership in the American Philosophical Society.

Wright married Louise Lane Williams in 1921, with whom he had three children, Richard, Robert, and Elizabeth Quincy Wright Rose. Louise Wright died in 1975, followed by Sewall on March 3, 1988, in Madison.

From the guide to the Sewall Wright Papers, 1885-1988, (American Philosophical Society)


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  • Heredity
  • Genetics
  • Evolution (Biology)
  • Population genetics
  • Evolution
  • Genetic algebras
  • Breeding


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