Hermann Joseph Muller

1890-1967

American Geneticist

Hermann Joseph Muller was a geneticist whose experiments with fruit flies demonstrated that x rays increase genetic mutations by altering gene structure. Upon discovering this connection, he began publicizing the danger of x rays and radiation, promoting radiation-safety measures, and fighting against nuclear bomb tests. His research on x rays was rewarded with the 1946 Nobel Prize for physiology or medicine.

Muller was born in New York City on December 21, 1890. He attended Morris High School in the Bronx, and then went on to Columbia University, where he received his bachelor's in 1910, his master's in 1911, and, after transferring briefly to Cornell University, his doctorate in 1916. During his years at Cornell, Muller was a member of Thomas Hunt Morgan's (1866-1945) research team. In 1910, the team verified that fruit flies had a fourth chromosome.

Before he earned his doctorate from Columbia, Muller became a biology instructor at Rice Institute and continued to hold a position there from 1915-1918. Next, he took a zoology instructor position at Columbia and then went on in 1920 to become an associate professor and then a professor of zoology at the University of Texas, where he remained for more than a decade.

During his changing faculty positions, Muller continued his genetics research. He was particularly interested in genetic mutations and set about trying to obtain a greater number of mutations than would occur naturally in the fruit flies he was studying. After finding in 1919 that heat heightened the mutation rate, he began to consider the reasons behind that increase and how he might enhance the effect. He deduced that x rays might exaggerate heat-related mutations, and over the next several years confirmed through experimentation that an x-ray application could increase the mutation rate by 150-fold. His finding, which he reported during an international scientific meeting, propelled him to scientific stardom. Using his technique, geneticists could now generate and study mutations in their research.

Despite the boon for genetics investigations, Muller saw the harmful side of this discovery as well, and began a crusade to publicize the dangerous nature of x rays, and to promote the safe use of radiation, particularly in health-care settings. When nuclear war loomed in the mid-1950s, he and many other scientists campaigned against the use of such weapons, with Muller concentrating on the potential the weapons posed for genetic mutations.

In addition, controversy swirled around him following the publication of his 1935 book Out of the Night, in which he described how the human race could be improved via artificial insemination using the sperm of particularly accomplished men.

On the professional side, Muller spent several years overseas, first as a researcher in Leningrad, and then in Moscow. When Soviet politics began to affect genetics research, Muller left Moscow and briefly served in a medical unit during the Spanish Civil War before moving on to spend two years at the Institute of Animal Genetics at the University of Edinburgh. Afterward, he returned to the United States, where he spent five years at Amherst College and then accepted a position as professor of zoology in 1945 at Indiana University, where he remained for the rest of his career. Over the years, he received many honors, including the Kimber Genetics Award in 1955, the Darwin Medal in 1959, and the Alexander Hamilton Award in 1960, in addition to the Nobel Prize in 1946. Muller died on April 5, 1967.

LESLIE A. MERTZ