H. J. Muller and science fiction Writer Ursula Le Guin were second cousins; his father (Hermann J. Muller Sr.) and her father's mother (Johanna Muller Kroeber) were siblings, the children of Nicholas Müller, who immigrated to the United States in 1848, and at that time dropped the umlaut from his name. Another cousin was Herbert J. Muller, whose grandfather Otto was another son of Nicholas and a sibling of Hermann Sr. and Johanna.
Hermann Joseph Muller (or H. J. Muller) (December 21, 1890 – April 5, 1967) was an American Geneticist, educator, and Nobel laureate best known for his work on the physiological and genetic effects of radiation (mutagenesis) as well as his outspoken political beliefs. Muller frequently warned of long-term dangers of radioactive fallout from nuclear war and nuclear testing, which resulted in greater public scrutiny of these practices.
In the USSR, Muller supervised a large and productive lab, and organized work on medical genetics. Most of his work involved further explorations of genetics and radiation. There he completed his eugenics book, Out of the Night, the main ideas of which dated to 1910. By 1936, however, Joseph Stalin's repressive policies and the rise of Lysenkoism was making the USSR an increasingly problematic place to live and work. Muller and much of the Russian genetics community did what they could to oppose Trofim Lysenko and his Larmarckian evolutionary theory, but Muller was soon forced to leave the Soviet Union after Stalin read a translation of his eugenics book and was "displeased by it, and...ordered an attack prepared against it."
Muller remained at Columbia (the pre-eminent American zoology program at the time, thanks to E. B. Wilson and his students) for graduate school. He became interested in the Drosophila genetics work of Thomas Hunt Morgan's fly lab after undergraduate bottle washers Alfred Sturtevant and Calvin Bridges joined his Biology Club. In 1911-1912, he studied metabolism at Cornell University, but remained involved with Columbia. He followed the drosophilists as the first genetic maps emerged from Morgan's experiments, and joined Morgan's group in 1912 (after two years of informal participation).
In 1914, Julian Huxley offered Muller a position at the recently founded william Marsh Rice Institute, now Rice University; he hurried to complete his Ph.D. degree and moved to Houston for the beginning of the 1915-1916 academic year (his degree was issued in 1916). At Rice, Muller taught biology and continued Drosophila lab work. In 1918, he proposed an explanation for the dramatic discontinuous alterations in Oenothera larmarckiana that were the basis of Hugo de Vries's theory of mutationism: "balanced lethals" allowed the accumulation of recessive mutations, and rare crossing over events resulted in the sudden expression of these hidden traits. In other words, de Vries's experiments were explainable by the Mendelian-chromosome theory. Muller's work was increasingly focused on mutation rate and lethal mutations. In 1918, Morgan—short-handed because many of his students and assistants were drafted for the U.S. entry into World War I—convinced Muller to return to Columbia to teach and to expand his experimental program.
Muller taught at The University of Texas from 1920 until 1932. Soon after returning to Texas, he married mathematics professor Jessie Marie Jacobs, whom he had courted previously. In his early years at Texas, Muller's Drosophila work was slow going; the data from his mutation rate studies were difficult to interpret. In 1923, he began using radium and X-rays, but the relationship between radiation and mutation was difficult to measure because such radiation also sterilized the flies. In this period, he also became involved with eugenics and human genetics. He carried out a study of twins separated at birth that seemed to indicate a strong hereditary component to I.Q. Muller was critical of the new directions of the eugenics movement (such as anti-immigration), but was hopeful about the prospects for positive eugenics.
1926 marked the beginning of a series of major breakthroughs. Beginning in November, Muller carried out two experiments with varied doses of X-rays, the second of which used the crossing over suppressor stock ("ClB") he had found in 1919. A clear, quantitative connection between radiation and lethal mutations quickly emerged. Muller's discovery created a media sensation after he delivered a paper entitled "The Problem of Genetic Modification" at the Fifth International Congress of Genetics in Berlin; it would make him one of the better known public intellectuals of the early 20th century. By 1928, others had replicated his dramatic results, expanding them to other model organisms such as wasps and maize. In the following years, he began publicizing the likely dangers of radiation exposure in humans (such as Physicians who frequently operate X-ray equipment).
In September 1932, Muller moved to Berlin to work with the Russian expatriate Geneticist Nikolay Timofeeff-Ressovsky, a trip intended as a limited sabbatical stretched into an eight-year, five-country journey. In Berlin, he met two physicists who would later be significant to the biology community: Niels Bohr and Max Delbrück. The Nazi movement was precipitating the rapid emigration of scientific talent from Germany, and Muller was particularly opposed to the politics of National Socialism. But the FBI was investigating Muller because of his involvement with The Spark, so he chose instead to go to the Soviet Union (an environment better suited to his political beliefs). In 1933, Muller and his wife reconciled, and she and their son David E. Muller moved with Hermann to Leningrad. There, at the Institute of Genetics, he imported the basic equipment for a Drosophila lab—including the flies—and set up shop. The Institute was moved to Moscow in 1934, and Muller and his wife were divorced in 1935.
When Muller returned to the United States in 1940, he took an untenured research position at Amherst College, in the department of Otto C. Glaser. After the U.S. entry into World War II, his position was extended indefinitely and expanded to include teaching. His Drosophila work in this period focused on measuring the rate of spontaneous (as opposed to radiation-induced) mutations. Muller's publication rate decreased greatly in this period, from a combination of lack of lab workers and experimentally challenging projects. However, he also worked as an adviser in the Manhattan Project (though he did not know that was what it was), as well as a study of the mutational effects of radar. Muller's appointment was ended after the 1944–1945 academic year, and despite difficulties stemming from his socialist political activities, he found a position as professor of zoology at Indiana University. Here, he lived in a Dutch Colonial Revival house in Bloomington's Vinegar Hill neighborhood.
In 1946 Muller was awarded the Nobel Prize in Physiology or Medicine, "for the discovery that mutations can be induced by x-rays". Genetics, and especially the physical and physiological nature of the gene, was becoming a central topic in biology, and X-ray mutagenesis was a key to many recent advances, among them George Beadle and Edward Tatum's work on Neurospora that established in 1941 the one gene-one enzyme hypothesis. In Muller's Nobel Prize lecture he argued that there was no threshold dose of radiation that did not produce mutagenesis, which led to the adoption of the linear no-threshold model of radiation on cancer risks.
The Nobel Prize, in the wake of the atomic bombings of Hiroshima and Nagasaki, focused public attention on a subject Muller had been publicizing for two decades: the dangers of radiation. In 1952, nuclear fallout became a public issue; since Operation Crossroads, more and more evidence had been leaking out about radiation sickness and death caused by nuclear testing. Muller—and many other scientists—pursued an array of political activities to defuse the threat of nuclear war. With the Castle Bravo fallout controversy in 1954, the issue became even more urgent. In 1955 Muller was one of eleven prominent intellectuals to sign the Russell-Einstein Manifesto, the upshot of which was the first 1957 Pugwash Conference on Science and World Affairs, which addressed the control of nuclear weapons. He was a signatory (with many other scientists) of the 1958 petition to the United Nations, calling for an end to nuclear weapons testing, which was initiated by the Nobel Prize-winning Chemist Linus Pauling.
Muller was awarded the Linnean Society of London's Darwin-Wallace Medal in 1958 and the Kimber Genetics Award of the U.S. National Academy of Sciences in 1955. He served as President of the American Humanist Association from 1956 to 1958. The American Mathematical Society selected him as its Gibbs Lecturer for 1958.
Muller is survived by his daughter, Helen J. Muller, now a professor emerita at the University of New Mexico, who has a daughter, Mala Htun. His son, David E. Muller, a professor emeritus of mathematics and computer science at the University of Illinois and at New Mexico State University, died in 2008 in Las Cruces, New Mexico. David's mother was Jessie Jacobs Muller Offermann, Hermann's first wife. Helen's mother was Dorothea Kantorowicz Muller, Hermann's second wife.
It has however been argued that Muller's opinions on the effect of radiation on mutagenesis were not supported by studies on the survivors of the atomic bombings, or in research on mice. Some Scientists have criticized the approach of Muller; James F. Crow called Muller's view "alarmist" and wrote that it created in the public "an irrational fear of low-level radiation relative to other risks". It is also argued that he was familiar with another study that directly contradicted the linear no-threshold model he supported, leading to a charge in 2011 that Muller misled the public as to the then-current data available and that would have an effect on the formulation of policy that favored his model.
Muller—with about 250 strains of Drosophila—moved to Edinburgh in September 1937, after a brief stay in Madrid and Paris. In 1938, with war on the horizon, he began looking for a permanent position back in the United States. He also began courting Dorothea "Thea" Kantorowicz, a German refugee; they were married in May 1939. The Seventh International Congress on Genetics was held in Edinburgh later that year; Muller wrote a "Geneticists' Manifesto" in response to the question: "How could the world's population be improved most effectively genetically?" He also engaged in a debate with the perennial genetics gadfly Richard Goldschmidt over the existence of the gene, for which there remained little direct physical evidence.