with natural selection as a major evolutionary process. According to de Vries (joined by other geneticists such as William Bateson in England), there are two kinds of variation in organisms. One is the “ordinary” variation observed among individuals of a species, which is of no lasting consequence in evolution because, according to de Vries, it could not “lead to a transgression of the species border even under conditions of the most stringent and continued selection.” The other consists of the changes brought about by mutations, spontaneous alterations of genes that yield large modifications of the organism and give rise to new species. According to de Vries, a new species originates suddenly, produced by the existing one without any visible preparation and without transition.

Mutationism was opposed by many naturalists, and in particular by the so-called biometricians, led by Briton Karl Pearson, who defended Darwinian natural selection as the major cause of evolution through the cumulative effects of small, continuous, individual variations (which the biometricians assumed passed from one generation to the next without being subject to Mendel’s laws of inheritance).

The controversy between mutationists (also referred to at the time as Mendelians) and biometricians approached a resolution in the 1920s and 1930s through the theoretical work of several geneticists (5). These geneticists used mathematical arguments to show, first, that continuous variation (in such characteristics as size, number of eggs laid, and the like) could be explained by Mendel’s laws; and second, that natural selection acting cumulatively on small variations could yield major evolutionary changes in form and function. Distinguished members of this group of theoretical geneticists were R.A.Fisher and J.B.S.Haldane in Britain and Sewall Wright in the United States (6–8). Their work contributed to the downfall of mutationism and, most importantly, provided a theoretical framework for the integration of genetics into Darwin’s theory of natural selection. Yet their work had a limited impact on contemporary biologists because it was formulated in a mathematical language that most biologists could not understand; because it was almost exclusively theoretical, with little empirical corroboration; and because it was limited in scope, largely omitting many issues, such as speciation, that were of great importance to evolutionists.

Dobzhansky’s Genetics and the Origin of Species advanced a reasonably comprehensive account of the evolutionary process in genetic terms, laced with experimental evidence supporting the theoretical arguments. It had an enormous impact on naturalists and experimental biologists, who rapidly embraced the new understanding of the evolutionary process as one of genetic change in populations. Interest in evolutionary studies was greatly stimulated, and contributions to the theory soon began to follow, extending the synthesis of genetics and natural selection to a variety of biological fields.

The main writers who, together with Dobzhansky, may be considered the architects of the synthetic theory were the zoologists Ernst Mayr (9) and Julian Huxley (10), the paleontologist George G.Simpson (11), and the botanist George Ledyard Stebbins (12). [The National Academy of Sciences held in January 1994 a colloquium (13) to commemorate the 50th anniversary of the publication of Simpson’s seminal book, Tempo and Mode in Evolution (11).] These researchers contributed to a burst of evolutionary studies in the traditional biological disciplines and in some emerging ones—notably population genetics and, later, evolutionary ecology. By 1950 acceptance of Darwin’s theory of evolution by natural selection was universal among biologists, and the synthetic theory had become widely adopted.

The line of thought of Genetics and the Origin of Species is surprisingly modern—in part, no doubt, because it established the pattern that successive evolutionary investigations and treatises largely would follow. Dobzhansky writes in the preface: “The problem of evolution may he approached in two different ways. First, the sequence of the evolutionary events as they have actually taken place in the past history of various organisms may be traced. Second, the mechanisms that bring about evolutionary changes may be studied…. The present book is dedicated to a discussion of the mechanisms of species formation in terms of the known facts and theories of genetics.” The book starts with a consideration of organic diversity and discontinuity. Successively, it deals with mutation as the origin of hereditary variation, the role of chromosomal rearrangements, variation in natural populations, natural selection, the origin of species by polyploidy, the origin of species through gradual development of reproductive isolation, physiological and genetic differences between species, and the concept of species as natural units. The book’s organization was largely preserved in the second. (1941) and third (1951) editions, and in Genetics of the Evolutionary Process (14), published in 1970, a book that Dobzhansky thought of as the fourth edition of the earlier one, but had changed too much for publication under the same title.

Dobzhansky sought to extend the evolutionary synthesis to mankind in numerous articles and several books, most notably Mankind Evolving (15), published in 1962, a book that many judge to be as important as Genetics and the Origin of Species. Dobzhansky was a leading experimentalist and prolific writer, who published several books and nearly 600 papers dealing with leading questions in population and evolutionary genetics, as well as with philosophical problems and humanistic issues. The experimental organisms of most of his research were Drosophila fruitflies.

Theodosius Dobzhansky was born on January 25, 1900, in Nemirov, a small town 200 km southeast of Kiev in the Ukraine. He was the only child of Sophia Voinarsky and Grigory Dobrzhansky (precise transliteration of the Russian family name includes the letter “r”), a teacher of high school mathematics. In 1910 the family moved to the outskirts of Kiev, where Dobzhansky lived through the tumultuous years of World War I and the Bolshevik revolution. In those times the family was often beset by various privations, including hunger.

In his unpublished autobiographical Reminiscences for the “Oral History Project” of Columbia University, Dobzhansky states that his decision to become a biologist was made about 1912. Through his early high school years, Dobzhansky became an avid butterfly collector. A school teacher gave him access to a microscope that Dobzhansky used particularly during the long winter months. In the winter of 1915–1916 he met Victor Luchnik, a 25-year-old college drop-out, who was a dedicated entomologist specializing in Coccinellidae beetles. Luchnik convinced Dobzhansky that butterfly collecting would not lead anywhere and that he should become a specialist. Dobzhansky chose to work with ladybird beetles, which would be the subject of his first scientific publication in 1918. (Reference to Dobzhansky’s publications can be found in the extensive bibliography published by the National Academy of Sciences, ref. 16.)

Dobzhansky graduated in biology from, the University of Kiev in 1921. Before his graduation, he was hired as an instructor in zoology at the Polytechnic Institute in Kiev. He taught there until 1924, when he became an assistant to Yuri Filipchenko, head of the new department of genetics at the University of Leningrad. Filipchenko was familiar with Thomas Hunt Morgan’s work in the United States and had started a Drosophila laboratory, where Dobzhansky was encouraged to investigate the pleiotropic effects of genes.

In 1927, Dobzhansky obtained a fellowship from the International Education Board (Rockefeller Foundation) and arrived in New York on December 27 to work with Thomas Hunt Morgan at Columbia University. In the summer of 1928 he