Theodosius Grigor'evich Dobzhansky

1900-1975

Russian-American Population Geneticist and Entomologist

Theodosius Dobzhansky (originally Feodosy Grigorevich Dobrzhanskii), one of the most influential biologists of the twentieth century, was born in the small city of Nemirov, Ukraine, on January 25, 1900. He was educated at home until 1910, when his parents moved to the outskirts of Kiev. He began to collect butterflies during his second year of Gymnasium (formal school) and by age 12 had decided to become a biologist. He attended his first amateur scientific excursion and was impressed by reading Charles Darwin's (1809-1882) Origin of Species at the age of 15.

At the Gymnasium Dobzhansky met Victor Luchnik (1892-1936), who invited Dobzhansky to join the local entomological society. On Luchnik's advice Dobzhansky decided to specialize in ladybird beetles (Coccinellidae) and began to collect and dissect them. His participation in this entomological circle influenced his later scientific ideas, leading him to study the morphology of sex organs as the defining trait for species.

In 1917 Dobzhansky graduated from the Gymnasium and began to work with Sergei Kushakevich (1878-1920), a professor at the University of Kiev. In the fall of that year Dobzhansky entered the Physico-Mathematical department of the university, where he received a broad education in natural science. He played an important role in assisting the geologist Vladimir Vernadsky (1863-1945). In 1921 Dobzhansky completed all of his courses at the university, although he never received a diploma. In 1918 he lost his father and two years later his mother.

Partially influenced by the cytologist Grigorii Levitskii (1878-1942) and the genetics publications of Yurii Filipchenko (1882-1929), Dobzhansky began investigating the genetics of Drosophila (fruit flies). His discovery of the correlation between the shape of genitalia and a geographic locality won him an invitation from Filipchenko to St. Petersburg University. Dobzhansky married Natalia Sivertsov, also a student of genetics, in 1925. On Filipchenko's nomination Dobzhansky won a Rockefeller Foundation fellowship to study with Thomas H. Morgan (1866-1945) at Columbia University. Dobzhansky departed for New York on December 6, 1927—never again to return to his homeland.

At the Morgan laboratory Dobzhansky worked with Alfred Sturtevant (1891-1970) and Calvin Bridges (1889-1938) in mapping Drosophila chromosomes. In 1928 the Morgan laboratory moved to the California Institute of Technology in Pasadena. During the 1930s Dobzhansky began to investigate the genetics of natural Drosophila populations. Based on his research he defined the formation of a new species in biological terms—as the change that occurs when two groups of a particular species (that were able to reproduce with each other) eventually became two distinct species (that could no longer produce fertile offspring).

In 1935 Dobzhansky delivered the Jessup Lectures at Columbia University, publishing them as Genetics and the Origin of Species (1937). This book became the foundation of the evolutionary "modern synthesis," which combined Mendelian genetics and the Darwinian theory of natural selection. Dobzhansky applied the theoretical work of Sewall Wright (1889-1988) to the study of natural populations, allowing him to address evolutionary problems in a novel way.

Dobzhansky was a synthesizer of genetic thought. In his nearly 600 publications, especially his series Genetics of Natural Populations (1938-1975), he drew on and extended the work of many researchers, including Nikolai Timofeev-Ressovsky (1900-1981) and Sergei Chetverikov (1880-1959). He also published several books on the relationship between biology, society, and religion. In Mankind Evolving (1962), for example, he discussed the moral concerns of natural selection when it is applied to human beings.

Between 1940 and 1962 Dobzhansky moved from Caltech to Columbia University in New York City, where he became professor of zoology. In 1962 he became professor emeritus at the Rockefeller Institute, a position he held until 1970, when he accepted his final position—adjunct professor at the University of California, Davis. Dobzhansky outlived his wife by six years, dying from heart failure in 1975.

LLOYD T. ACKERT JR.