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A second look at how life began on Earth

Column: By reexamining early experiments, scientists draw new conclusions.

NASA

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Scientists who study the rise of earthly life take their work with a grain of salt. They know that reanalysis of old data can jerk their theories around. Two such cases – a new look at some 55-year-old “primordial soup” experiments and a reexamination of the “oldest fossils” of photosynthetic microbes – illustrate this point.

In 1953, the late Stanley Miller published what became the most famous experiments in pre-life biochemistry. He discharged electric sparks through mixtures of ammonia, hydrogen, and methane, which he thought were abundant in Earth’s early atmosphere. This effort produced chemical residues containing amino acids, which are the building blocks of proteins. That made a good case for believing that lightning in the early atmosphere literally sparked a chemical reaction that eventually led to organic life itself. But as early Earth research progressed, geophysicists came to doubt that the primitive atmosphere had the mix of chemicals Mr. Miller’s experiments assumed.

Fast forward to the 21st century. When Miller died last year, Jeffrey Bada at Scripps Institution of Oceanography in San Diego and Adam Johnson at Indiana University in Bloomington found vials containing dried chemical residues from the original experiments among Miller’s effects. Dr. Bada says it was “a great opportunity to reanalyze these historic samples using modern methods.”

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