To explore how molecules became signs I will ask: “What sort of process is necessary and sufficient to treat a molecule as a sign?” This requires focusing on the interpreting system and its interpretive competence. To avoid assuming any properties that need to be explained I develop what I consider to be a simplest possible molecular model system which only assumes known physics and chemistry but nevertheless exemplifies the interpretive properties of interest. Three progressively more complex variants of this model (...) of interpretive competence are developed that roughly parallel an icon-index-symbol hierarchic scaffolding logic. The implication of this analysis is a reversal of the current dogma of molecular and evolutionary biology which treats molecules like DNA and RNA as the original sources of biological information. Instead I argue that the structural characteristics of these molecules have provided semiotic affordances that the interpretive dynamics of viruses and cells have taken advantage of. These molecules are not the source of biological information but are instead semiotic artifacts onto which dynamical functional constraints have been progressively offloaded during the course of evolution. (shrink)