Biographical Memoirs Volume 64 (1994) / Chapter Skim
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Sewall Wright
Sewall Wright
Pages 438-470
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From page 439... ...
In acictition, he was a pioneer in physiological genetics and was uniquely responsible for the developmental en c! coatcolor genetics of guinea pigs.
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He also printed the Lombard College bulletin on his own printing press. Later, he did research at the Brookings Institution and published several books; one, The Tariff on Animal and Vegetable Oils, included a statistical appendix by his son Sewall.
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He took math courses from his father, going as far as differential and integral calculus. He never took any acivanced mathematics and his later theoretical work in population genetics clependec!
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Wright playocl a crucial role by suggesting the experiments to distinguish between the view, wrongly held by Castle, that the color changes were in the major gene itself, and the opposing (anc! correct)
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During this period Wright also developed what he later called the "shifting balance theory." In 1926 he moved to the University of Chicago where he continued his theoretical work as well as his experiments with guinea pigs. He also took up the standard academic duties, teaching several courses and supervising graduate students.
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These were: correlation analysis, animal breeding, and mammalian physiological genetics. His evolutionary ideas followeci soon after.
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From such a diagram Wright found simple rules by which one can easily write all the appropriate equations. The method has the virtue of making immediately obvious whether there are enough ciata and relationships to permit a solution.
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Wright's ( 1922, 2-4) studies on inbreeding and crossbreeding of guinea pigs, utilizing the accumulatecl USDA records and ciata of his own, were masterful.
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The steady improvement of milk production testifies to the effectiveness of a well-organized, cooperative selection program. The current methods superficially look quite different from path analysis, but they trace back to the Wright-Lush influence.
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Throughout his guinea pig studies Wright went as far toward a chemical explanation as knowlecige of the time would permit; he wanted to explain (luminance and epistasis in chemical terms. His quantitative bent led him to formulate the relationships in path diagrams and to express the kinetics as differential equations, assuming flux equilibrium kinetics.
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From page 449... ...
He showed in his "Fun(lamental Theorem of Natural Selection" that, regardless of gene interactions, selection acts on the acIditive (least squares linear) component of the genetic variance.
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So he argued that the best chance for the evolution of harmonious gene combinations lies in the population structure. In a population cliviclect into many local populations between which there is limited interchange, the gene frequencies will vary randomly in each of them (provicled the size is small enough)
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From page 451... ...
Fisher's "fundamental theorem of natural selection" is concerned with the total combined effects of alleles at multiple loci under the assumption of panmixia in the species as a whole. He recognized that it was an exceedingly slow process.
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Wright's work in population genetics was almost entirely theoretical, but he had an important collaboration with Th. Dobzhansky.
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Wright was quick to say that his philosophical views had little relevance to the day-to-day practice of science, and philosophy hardly ever entered his conversations with biological colleagues. WRIGHT'S IMPACT Wright made lasting contributions in statistics, mammalian genetics, animal breeding, population genetics, and the theory of evolution.
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It is a treasure of information for those who would like to know more than can be presented in this short article. I have also drawn freely on my own earlier writings, listed in the references below.
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From page 455... ...
F Crow, "Sewall Wright and Physiological Genetics," Genetics, 115(1987)
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Received B.S. from Lombard College, which later merged with Knox College.
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F Meckel Prize, American Society of Medical Genetics 1984 Balzan Prize, Balzan Foundation, Milano MEMBERSHIPS National Academy of Sciences American Philosophical Society American Academy of Arts and Sciences American Association for the Advancement of Science American Genetics Association American Statistical Association Genetics Society of America Biometric Society Royal Society of London (Foreign Member)
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From page 458... ...
1916 An intensive study of the inheritance of color and of other coat characters in guinea pigs with especial reference to graded variation. Carnegie Institute Washington Publ.
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Factors in the resistance of guinea pigs to tuberculosis with special regard to inbreeding and heredity.
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1927 With Leo Loeb. Transplantation and individuality differentials in inbred families of guinea pigs.
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Types of subnormal development of the head from inbred strains of guinea pigs and their bearing on the classification and interpretation of vertebrate monsters.
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Genetics 19:506-36. The results of crosses between inbred strains of guinea pigs differing in number of digits.
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Genetics 27:363-94. The physiological genetics of coat color of the guinea pig.
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XII. Experimental reproduction of some of the changes caused by natural selection in certain populations of Drosophila pseudoobscura.
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113:3364. Discussion on population genetics and radiation.
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Cold Springs Harbor Symp. Quant.
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Postnatal changes in the intensity of coat color in diverse genotypes of the guinea pig. Genetics 45:1503-29.
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103:56174. 1970 Random drift and the shifting balance theory of evolution.
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From page 469... ...
35:757-68. 1984 The first Meckel oration: On the causes of morphological differences in a population of guinea pigs.
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