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The other theory argues that replication based on nucleic acids (RNA and/or DNA) came after biological entities could support metabolism. Günter Wächtershäuser proposed a version of this metabolism-first theory in which hot water from volcanoes flowed over mineral-rich rocks to ignite (catalyze) chemical reactions that fused simple carbon-based compounds into larger ones. While catalytic enzymes, which are proteins, did not yet exist, minerals, such as those in rocks, can and do function as prebiotic catalysts for chemical reactions. According to this theory, a key step occurred when, through a series of these prebiotic reactions, the circle was closed by the regeneration of the original compound. Through such a process, complex biological molecules (proteins, nucleotides, lipids, and carbohydrates) could be made, forming the basis of simple protocells that made energy and replicated.
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Joseph E. LeDoux (The Deep History of Ourselves: The Four-Billion-Year Story of How We Got Conscious Brains)