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While we don't know precisely how life got its start on Earth, most scientists accept what's called the "RNA world" hypothesis, which posits that RNA molecules kickstarted the process by acting as both catalysts and genetic material. This does, however, leave an awkward question: how did proteins get involved?

Proteins are long chains of chemicals called amino acids, and it's not clear how or why these molecules would have become associated with RNAs. Now, some research published in Angewandte Chemie is suggesting that chains of amino acids could have formed spontaneously, driven by nothing more than a cyclical dry period.

Amino acids are just what their name implies: they have an acidic group on one side of the molecule and a nitrogen-containing amino group on the other. It's possible to link these two groups together in a reaction that releases a water molecule. Once linked, they're stable, but the reaction that links them isn't energetically favorable. So, people pondering the origin of life have wondered whether there was a pathway in which the bond could form spontaneously.

One possible method for getting it to form would be for a solution of amino acids to dry out. As the solution becomes ever more concentrated, a reaction that produces a water molecule could become favorable even if it's expensive in purely energetic terms. But so far, the reaction conditions to get this to work have been rather extreme...

Repeated drying cycles can form protein-like polymers | Ars Technica

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