March 7, 2011

Happy Birthday, Stanley Miller

This guy asked a question a lot of people have asked before and since:

How did life on Earth get started?

Although many religions offer stories about the beginning of the world and of life, science is based on evidence and testable ideas called hypotheses. Some people think there's no way we can use science to figure out what happened in the past—but of course there's tons of evidence we can study and many experiments we can run to find out about things that happened in the past—yesterday, last month or year, history and pre-history and pre-pre-history. (Just ask any detective or CSI unit!)

Stanley Miller, who was born in California on this day in 1930, wondered what would happen if he and his colleagues could experimentally re-create conditions believed to exist on Earth billions of years ago. In 1952 they created a mixture of ammonia, methane, hydrogen—an atmosphere like that of Jupiter in the present—plus water, and they introduced an electrical charge as an energy source, since there was (and still is) lightning. Amino acids and other organic compounds were created (although of course actual, self-replicating life wasn't, nor was expected to be, created!).

This classic experiment on the origins of life is called the Miller-Urey experiment.

After operating the apparatus continuously for a week, Miller reported that 11 out of 20 amino acids had formed. Note that scientists didn't expect to create functioning cells or self-replicating life in just a week of simulated early-Earth conditions! After all, life may have arisen after the build-up of organic molecules and amino acids after millions and millions of years, possibly even an entire thousand million (otherwise known as a billion) years.

When Stanley Miller died in 2007, scientists examined some sealed vials preserved from the original experiment and found that there were more than 20 different amino acids—not the mere 11 Miller reported.

Since the Miller-Urey experiment, discoveries have indicated that the early Earth environment included a lot of volcanic eruptions and that the atmosphere would have been richer in compounds, including carbon dioxide, nitrogen, hydrogen sulfide, and sulfur dioxide, that would provide even more material for organic molecules. Subsequent origin-of-life experiments have produced many more diverse organic molecules.

By the way, the study of how life on Earth began is called abiogenesis.

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