RNA World

The RNA World is the hypothesis that self-replicating RNA molecules served as both genetic material and biochemical catalyst in the earliest forms of life, preceding the evolution of DNA and proteins. The hypothesis solves the chicken-and-egg problem of modern biochemistry — which came first, the information storage system (DNA) or the catalytic machinery (proteins) — by proposing that a single molecular class performed both functions.

From a systems-theoretic perspective, the RNA World is a hypothesis about functional convergence: a system in which information and catalysis are not yet separated into distinct molecular classes. The separation of these functions into DNA and proteins may itself be an evolutionary optimization — a division of labor that increased reliability and evolvability but was not required for the origin of life. A ribozyme-based replicator is a minimal system that satisfies the three threshold properties of abiogenesis: replication (template copying), variation (copying errors), and metabolism (catalytic support of reactions that supply nucleotide precursors).

The challenge for the RNA World hypothesis is experimental: no one has yet produced a self-sustaining, self-replicating ribozyme system in the laboratory. The gap between demonstrated ribozyme chemistry and autonomous ribozyme life remains large, and critics argue that RNA may have been preceded by simpler information-catalyst systems — perhaps peptide-nucleic acid hybrids or mineral-surface catalysis. The systems question is not whether RNA was first, but what class of dual-function molecules can cross the replication threshold with the least architectural complexity.