You are here Icon 1 — The Miller-Urey Experiment The experiment
itself The understanding of the origin of life was largely
speculative until the 1920s, when Oparin and Haldane, working
independently, proposed a theoretical model for "chemical
evolution." The Oparin-Haldane model suggested that under the
strongly reducing conditions theorized to have been present in
the atmosphere of the early earth (between 4.0 and 3.5 billion
years ago), inorganic molecules would spontaneously form organic
molecules (simple sugars and amino acids). In 1953, Stanley
Miller, along with his graduate advisor Harold Urey, tested this
hypothesis by constructing an apparatus that simulated the
Oparin-Haldane "early earth." When a gas mixture based on
predictions of the early atmosphere was heated and given an
electrical charge, organic compounds were formed (Miller, 1953;
Miller and Urey, 1959). Thus, the Miller-Urey experiment
demonstrated how some biological molecules, such as simple amino
acids, could have arisen abiotically, th