Recooking the Recipe for Prebiotic Soup: Scripps Professor Revisits the Miller Experiment and the Origin of Life

Scripps Institution of Oceanography / University of California, San Diego

In the fall of 1952, Stanley Miller, now a chemistry professor emeritus at the University of California, San Diego (UCSD), began simulating primitive earthly conditions in an experiment that produced the basic building blocks of life. When he published the results in Science on May 15 the following year, he kick-started research on the origin of life and transformed modern thinking on a dormant area of science.

Jeffrey Bada, a professor of marine chemistry at Scripps Institution of Oceanography, UCSD, and an expert on origin of life processes, revisits the famous "Miller experiment" in a report published in the May 2 issue of Science.

"Up to Miller's experiment there was a large vacuum in our understanding of how life began on the earth," said Bada, who coauthored the report with Antonio Lazcano, a scientist at the Universidad Nacional Autónoma de México, and is a visiting scholar at UCSD in Miller's laboratory. "Up to that point no one had demonstrated how compounds like amino acids could be synthesized under possible early Earth conditions."

Bada and Lazcano's essay traces the history of the Miller experiment, which originated when the late Nobel Laureate and UCSD Chemistry Professor Harold Urey discussed the idea behind the experiment in a lecture at the University of Chicago. Miller, then a graduate student in the audience, eventually presented Urey the idea of a prebiotic synthesis experiment applying an electric discharge to a mixture of methane, ammonia, water vapor, and hydrogen. Urey eventually agreed to the idea.

Results of the famous Miller experiment, which used the glass apparatus pictured, were published by Science 50 years ago. The lower flask was designed to simulate the oceans and the upper flask the atmosphere. The energy was supplied by sparking between two wire electrodes.

During Miller's experiment, the mixture of gases was circulated through a liquid water solution and continuously zapped with the electric spark, which substituted for lightning. The surprising products of the process were "biochemically significant" compounds such as amino acids, hydroxy acids, and urea. Thus, with Urey's guidance, Miller had produced the basic building blocks of contemporary life forms on Earth.

"In the early 1950s, several groups were attempting organic synthesis under primitive conditions," Bada and Lazcano note in their essay. "But it was the Miller experiment, placed in the Darwinian perspective provided by Oparin's ideas and deeply rooted in the 19th century tradition of synthetic organic chemistry, that almost overnight transformed the study of the origin of life into a respectable field of inquiry."

Bada and Lazcano also note that Miller's study was published only a few weeks after Watson and Crick's landmark paper on the DNA double-helix model and the authors highlight the important link between the two young fields in the years that followed.

EVENT NOTE: Bada will be giving a public lecture on the 50th anniversary of the Miller experiment at 3 p.m. on Tuesday, June 10, 2003, during "Celebrating 50 Years of Prebiotic Chemistry," a public event at the Robinson Building Complex Auditorium, Graduate School of International Relations & Pacific Studies (IR/PS), Thurgood Marshall College, UCSD campus. The event, which also features Gerald Joyce of the Scripps Research Institute, is sponsored by the NASA Specialized Center of Research and Training (NSCORT) in Exobiology, the UCSD Dean of Physical Sciences, the Department of Chemistry and Biochemistry at UCSD, and the National Aeronautics and Space Administration. For information about the event: 858/534-1891; or visit the NSCORT/Exobiology web site at http://exobio.ucsd.edu. Scripps Institution of Oceanography on the web: http://scripps.ucsd.edu Scripps News on the web: http://scrippsnews.ucsd.edu Scripps Centennial on the web: http://scripps100.ucsd.edu