Theodosius Dobzhansky

Theodosius Dobzhansky helped create the Modern Synthesis of Evolution
National Institutes of Health

Early Life and Education

Born January 24, 1900 - Died December 18, 1975

Theodosius Grygorovych Dobzhansky was born on January 24, 1900 in Nemyriv, Russia to Sophia Voinarsky and math teacher Grigory Dobzhansky. The Dobzhansky family moved to Kiev, Ukraine when Theodosius was ten years old. As an only child, Theodosius spent much of his high school years collecting butterflies and beetles and studying Biology.

Theodosius Dobzhansky enrolled in the University of Kiev in 1917 and finished his studies there in 1921. He stayed and taught there until 1924 when he moved to Leningrad, Russia to study fruit flies and genetic mutations.

Personal Life

In August of 1924, Theodosius Dobzhansky married Natasha Sivertzeva. Theodosius met the fellow geneticist while working in Kiev where she was studying evolutionary morphology. Natasha's studies led Theodosius to take more interest in the Theory of Evolution and incorporate some of those findings in his own genetics studies.

The couple had only one child, a daughter named Sophie. In 1937, Theodosius became a citizen of the United States after working there for several years.


In 1927, Theodosius Dobzhansky accepted a fellowship from the International Educational Board of the Rockefeller Center to work and study in the United States. Dobzhansky moved to New York City to begin work at Columbia University.

His work with fruit flies in Russia was expanded at Columbia where he studied in the "fly room" established by geneticist Thomas Hunt Morgan.

When Morgan's lab moved to California at the California Institute of Technology in 1930, Dobzhansky followed. It was there that Theodosius did his most famous work studying fruit flies in "population cages" and relating the changes that were seen in the flies to the Theory of Evolution and Charles Darwin's ideas of Natural Selection.

In 1937, Dobzhansky wrote his most famous book Genetics and the Origin of Species. It was the first time someone had published a book correlating the field of genetics with Charles Darwin's book. Dobzhansky redefined the term "evolution" in genetics terms to mean "a change in the frequency of an allele within a gene pool". It followed that Natural Selection was driven by mutations in a species' DNA over time.

This book was the catalyst for the Modern Synthesis of the Theory of Evolution. While Darwin had proposed a supposed mechanism for how Natural Selection worked and evolution happened, he was unaware of genetics since Gregor Mendel had not yet done his work with pea plants at that time. Darwin knew that traits were passed down from parents to offspring generation after generation, but he did not know the actual mechanism of how that happened. When Theodosius Dobzhansky wrote his book in 1937, much more was known about the field of Genetics, including the existence of genes and how they mutated.

In 1970, Theodosius Dobzhansky published his final book Genetics and the Evolutionary Process that spanned 33 years of his work on the Modern Synthesis of the Theory of Evolution. His most enduring contribution to the Theory of Evolution was perhaps the idea that changes in species over time was not gradual and many different variations could be seen in populations at any given time.

He had witnessed this countless times when studying fruit flies throughout this career.

Theodosius Dobzhansky was diagnosed in 1968 with leukemia and his wife Natasha died shortly after in 1969. As his illness progressed, Theodosius retired from active teaching in 1971, but took an Emeritus Professor position at the University of California, Davis. His often quoted essay "Nothing in Biology Makes Sense Except in the Light of Evolution" was written after his retirement. Theodosius Dobzhansky died on December 18, 1975.