Amino Acids Entered Life's Code in Multiple Ways, Scientists Say

A University of Arizona-led analysis rethinking the origin of life suggests the 20 canonical amino acids may have entered the genetic code from multiple abiotic routes rather than a single sequential order. Building on a 2024 PNAS study of protein domains in LUCA, newer work shows amino acids could originate from diverse early-Earth chemistry and that core cellular machinery can function with a reduced amino‑acid alphabet in engineered cells. This challenges the view that tryptophan was the last amino acid added and has implications for our understanding of early protolife on Earth and the search for life elsewhere, including oceans on Enceladus.