Amino Acids May Have Arrived Out of Order, Rewriting Life's Origins
A University of Arizona study published in PNAS suggests the first amino acids did not appear in a simple, global sequence as traditionally thought. By analyzing the evolution of protein domains dating to LUCA, researchers find that tryptophan was more common in pre-LUCA life than post-LUCA, implying a more complex and regionally diverse origin of amino acids and a potentially ancient, diverse genetic code. These results challenge established timelines for life's beginnings and hint that amino acids could form in non-Earth environments, widening the search for extraterrestrial life (e.g., Enceladus' subsurface ocean).