Iconography has played a central role in the development of writing systems. That all independently derived ancient scripts began as arrangements of pictograms before evolving into their elaborated forms evinces the fundamental importance of iconography in the evolution of writing. Symbols of the earliest logographic writing systems are characterized by a number of iconographic principles. Elucidation of these iconographic principles provides a theoretical framework for the analysis of structural similarities in unrelated, independently evolved writing systems. Two such writing systems are the ancient Indus Valley and Easter Island scripts. Although separated by vast tracts of time and space, the two writing systems share between forty and fifty complex characters, a problem first identified by Hevesy in 1932. Previous attempts to explain the similarities between the Indus Valley script and the rongorongo of Easter Island, which have relied on notions of cultural contact or historical derivation, have proved unfruitful. In reconsidering the problem, a novel approach based on comparative iconographic principles can explain the resemblances between the two scripts as the product of the universal iconography displayed by all writing systems in their pictographic and logographic stages of development.