Hermann Joseph Muller (most commonly referred to as H. J. Muller) (December 21, 1890 - April 5, 1967) was an American geneticist and educator. In 1946 he was awarded the Nobel Prize, "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 scientific advancements. He is also remembered for his outspoken political beliefs, and frequently warned of the long-term dangers of radioactive fallout from nuclear war and nuclear testing. In 1955 he was one of eleven prominent intellectuals to sign the Russell-Einstein Manifesto. He was a signatory 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. He was awarded the Linnean Society of London's prestigious Darwin-Wallace Medal in 1958, and served as president of the American Humanist Association from 1956 to 1958. He died in 1967 at the age of 76.