Before photosynthesis emerged and filled the atmosphere with oxygen, Earth was essentially an oxygen-free zone, teeming with iron in its soluble 2+ form. Under those conditions, researchers report, ribonucleic acid could have been capable of even more feats than it is today (Nat. Chem. 2013, DOI: 10.1038/nchem.1649). RNA needs cations to fold properly, to catalyze chemical reactions, and to bind to other molecules. In most of modern biology, it uses magnesium cations. To examine what RNA would be like under prephotosynthetic conditions, Loren D. Williams and colleagues at Georgia Institute of Technology replaced RNA’s magnesium with iron while excluding oxygen. Sure enough, some of their RNA sequences became capable of catalyzing single-electron transfer reactions. This type of reduction reaction hasn’t been attributed to RNA before. The authors, who are part of the NASA Astrobiology Institute Center for Ribosomal Origins & Evolution, say their work implies that under these ancient conditions, RNA could have catalyzed the formation of DNA building blocks.