Miller, Stanley L. (1930- )

American chemist

Stanley Lloyd Miller is most noted for his experiments that attempted to replicate the chemical conditions that may have first given rise to life on Earth. In the early 1950s he demonstrated that amino acids could have been created under primordial conditions. Amino acids are the fundamental units of life; they join together to form proteins, and as they grow more complex they eventually become nucleic acids, which are capable of replicating. Miller has hypothesized that the oceans of primitive Earth were a mass of molecules, a prebiological "soup," which over the course of a billion years became a living system.

Miller was born in Oakland, California, the younger of two children. His father, Nathan Harry Miller, was an attorney and his mother, Edith Levy Miller, was a homemaker. Miller attended the University of California at Berkeley and received his B.S. degree in 1951. He began his graduate studies at the University of Chicago in 1951.

In an autobiographical sketch entitled "The First Laboratory Synthesis of Organic Compounds under Primitive Earth Conditions," Miller recalled the events that led to his famous experiment. Soon after arriving at the University of Chicago, he attended a seminar given by Harold Urey on the origin of the solar system. Urey postulated that the earth was reducing when it was first formed—in other words, there was an excess of molecular hydrogen. Strong mixtures of methane and ammonia were also present, and the conditions in the atmosphere favored the synthesis of organic compounds. Miller wrote that when he heard Urey's explanation, he knew it made sense: "For the nonchemist the justification for this might be explained as follows: it is easier to synthesize an organic compound of biological interest from the reducing atmosphere constituents because less chemical bonds need to be broken and put together than is the case with the constituents of an oxidizing atmosphere."

After abandoning a different project for his doctoral thesis, Miller told Urey that he was willing to design an experiment to test his hypothesis. However, Urey expressed reluctance at the idea because he considered it too time consuming and risky for a doctoral candidate. But Miller persisted, and Urey gave him a year to get results; if he failed he would have to choose another thesis topic. With this strict deadline Miller set to work on his attempt to synthesize organic compounds under conditions simulating those of primitive earth.

Miller and Urey decided that ultraviolet light and electrical discharges would have been the most available sources of energy on Earth billions of years ago. Having done some reading into amino acids, Miller hypothesized that if he applied an electrical discharge to his primordial environment, he would probably get a deposit of hydrocarbons, organic compounds containing carbon and hydrogen. As he remembered in "The First Laboratory Synthesis of Organic Compounds": "We decided that amino acids were the best group of compounds to look for first, since they were the building blocks of proteins and since the analytical methods were at that time relatively well developed." Miller designed an apparatus in which he could simulate the conditions of prebiotic Earth and then measure what happened. A glass unit was made to represent a model ocean, atmosphere, and rain. For the first experiment, he filled the unit with the requisite "primitive atmosphere"—methane, hydrogen, water, and ammonia—and then submitted the mixture to a low-voltage spark over night. There was a layer of hydrocarbons the next morning, but no amino acids.

Miller then repeated the experiment with a spark at a higher voltage for a period of two days. This time he found no visible hydrocarbons, but his examination indicated that glycine, an amino acid, was present. Next, he let the spark run for a week and found what looked to him like seven spots. Three of these spots were easily identified as glycine, alpha-alanine, and beta-alanine. Two more corresponded to a-aminon-butyric acid and aspartic acid, and the remaining pair he labeled A and B.

At Urey's suggestion, Miller published "A Production of Amino Acids under Possible Primitive Earth Conditions" in May of 1953 after only three-and-a-half months of research. Reactions to Miller's work were quick and startling. Articles evaluating his experiment appeared in major newspapers; when a Gallup poll asked people whether they thought it was possible to create life in a test tube; seventy-nine percent of the respondents said no.

After Miller finished his experiments at the University of Chicago, he continued his research as an F. B. Jewett Fellow at the California Institute of Technology from 1954 to 1955. Miller established the accuracy of his findings by performing further tests to identify specific amino acids. He also ruled out the possibility that bacteria might have produced the spots by heating the apparatus in an autoclave for eighteen hours (fifteen minutes is usually long enough to kill any bacteria). Subsequent tests conclusively identified four spots that had previously puzzled him. Although he correctly identified the a-amino-n-butyric acid, what he had thought was aspartic acid (commonly found in plants) was really iminodiacetic acid. Furthermore, the compound he had called A turned out to be sarcosine (N-methyl glycine), and compound B was N-methyl alanine. Other amino acids were present but not in quantities large enough to be evaluated.

Although other scientists repeated Miller's experiment, one major question remained: was Miller's apparatus a true representation of the primitive atmosphere? This question was finally answered by a study conducted on a meteorite that landed in Murchison, Australia, in September 1969. The amino acids found in the meteorite were analyzed and the data compared to Miller's findings. Most of the amino acids Miller had found were also found in the meteorite. On the state of scientific knowledge about the origins of human life, Miller wrote in "The First Laboratory Synthesis of Organic Compounds" that "the synthesis of organic compounds under primitive earth conditions is not, of course, the synthesis of a living organism. We are just beginning to understand how the simple organic compounds were converted to polymers on the primitive earth...nevertheless we are confident that the basic process is correct."

Miller's later research has continued to build on his famous experiment. He is looking for precursors to ribonucleic acid (RNA ). "It is a problem not much discussed because there is nothing to get your hands on," he told Marianne P. Fedunkiw in an interview. He is also examining the natural occurrence of clathrate hydrates, compounds of ice and gases that form under high pressures, on the earth and other parts of the solar system.

Miller has spent most of his career in California. After finishing his doctoral work in Chicago, he spent five years in the department of biochemistry at the College of Physicians and Surgeons at Columbia University. He then returned to California as an assistant professor in 1960 at the University of California, San Diego. He became an associate professor in 1962 and eventually full professor in the department of chemistry.

Miller served as president of the International Society for the Study of the Origin of Life (ISSOL) from 1986 to 1989. The organization awarded him the Oparin Medal in 1983 for his work in the field. Outside of the United States, he was recognized as an Honorary Councilor of the Higher Council for Scientific Research of Spain in 1973. In addition, Miller was elected to the National Academy of Sciences. Among Miller's other memberships are the American Chemical Society, the American Association for the Advancement of Science, and the American Society of Biological Chemists.

See also Evolution and evolutionary mechanisms; Evolutionary origin of bacteria and viruses; Miller-Urey experiment