One of the big mysteries in biology is how early organisms got started from pre-biotic conditions. In other words, how did self-replicating organic molecules develop from inorganic chemicals?
In an attempt to answer this nagging question, in the 1950s, two University of Chicago researchers, Stanley Miller and Harold Urey, performed a strange experiment. They ran electrical sparks through a mixture of gases that (at the time) were presumed to have been present in Earth’s atmosphere more than 3 billion years ago.
The results of this classic experiment were at the time astounding. Electricity running through the gas mixture produced a sludgy mess that proved to contain five amino acids, the building blocks of proteins and self-replicating molecules like DNA and RNA.
As it turns out, Miller and Urey had used two other slightly different set ups, and the results from the those they apparently ignored, since they appeared to be less successful. Still, Miller, who died in 2007, stashed the “failed” apparatus away — perhaps for posterity.
It’s a good thing he did. Researchers at Indiana University-Bloomington recently ran the sludge from the other experiments through modern analytical equipment, uncovering not five amino acids, but 22!
The 1953 Urey-Miller experiment assumed that pre-biotic Earth had a reducing atmosphere, a mixture of methane, ammonia, hydrogen and water vapor, torn by violent thunderstorms. Planetologists, however, now assume early Earth’s air had a different mix of gases than Urey and Miller had assumed, and that volcanoes, not lightning, provided the energy to get the ball rolling.
The latest results, however, vindicate the basic premise: it is possible to create a wide variety of complex organic molecules from basic molecules. The Indiana results also suggest that this mechanism could have produced complex organic molecules elsewhere in our solar system.
The full report is in the latest edition of Science. If you don’t have full access to Science, here’s a summary at physorg.com. For background on the original experiment, check here.
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