Life on Earth may have emerged twice. Researchers studied the protein structures of enzymes in the genomes of bacteria and archaea, and found "cases where the ancestors of bacteria and archaea independently evolved structurally distinct enzymes to catalyze the same essential metabolic reaction."

Life on Earth may have emerged twice. Researchers studied the protein structures of enzymes in the genomes of bacteria and archaea, and found "cases where the ancestors of bacteria and archaea independently evolved structurally distinct enzymes to catalyze the same essential metabolic reaction."