SEWALL WRIGHT
James F. Crow
Sewall Wright was one of the great trio, R. A. Fisher, J. B. S. Haldane, and
himself, who, starting about the time of World War I, founded the mathematical
theory of microevolution and population genetics. Until the end of World War
II, these three almost totally dominated the field. Wright’s three most important
contributions, all mathematical in nature, are: the theory of inbreeding and popu-
lation structure, the shifting-balance theory of evolution, and the method of path
analysis. But these are only part of a long and extremely productive scientific life.
He was also a rarity among biologists in contributing to philosophy: his theory of
organism and the mind-body problem.
After a brief biography, I discuss Wright’s contributions to inbreeding theory,
statistics, physiological genetics, population genetics, evolution, and philosophy.
At the end I have added a short section on Sewall Wright the man — his character
and personality.
Much of this material is taken from a more detailed article[Crow, 1992].For
more details of Wright’s life, both personal and scientific, see Provine’s book
[Provine, 1986]. Wright has summarized in four volumes most of his own work as
well as that of many others[Wright, 1968-78].
1 ABIOGRAPHYINBRIEFSewall Wright was born in Melrose, Massachusetts on December 21, 1889. Shortly
afterward, his father accepted a teaching position at Lombard College in Galesburg
Illinois, where Sewall grew up. He was a precocious child, being able to read, write,
and do arithmetic before starting school. He astonished his first grade teacher by
knowing how to extract cube roots. At the teacher’s request, he demonstrated
this at the blackboard for the eighth grade class. The consequence, he said, was
instant unpopularity with the other students. Thereafter he remained studiously
quiet in class, rarely volunteering anything.
In due course he enrolled at Lombard College, where his father taught an aston-
ishing variety of courses, including mathematics, surveying, astronomy, and En-
glish composition, in addition to his own subject, economics. Later he joined the
Brookings Institute and wrote several books on economic policies. Sewall Wright
had two brothers, Quincy who became widelly known as a scholar of international
law and Theodore, equally well known in aeronautical engineering.
Many of Wright’s college courses were taught by his father. Although most
biologists regard Wright as a formidable mathematician, actually what he didn’t
General editors: Dov M. Gabbay,
©c2007 Elsevier B.V. All rights reserved.
Handbook of the Philosophy of Science. Philosophy of Biology
Volume editors:
Paul Thagard and John WoodsMohan Matthen and Christopher Stephens