Explaining culture through contagion mechanics has appealed to some anthropologists, from a theoretical standpoint, and some quantitative sociologists have proposed formal models for this phenomenon. Studying the spread of culture through the lens of epidemiology has a kind of natural appeal, as it seems to intuitively make sense. The dynamics of epidemics, with their sometimes explosive behavior in a pandemic, combined with oscillations or endemic patterns, seem to capture the phase transitions of cultural spread. The particular links between economics and epidemiology were surveyed in Avery et al. (2020): economics can bring new perspectives in epidemiological modeling by endogenizing certain parameters, which can have a significant impact on how contagion dynamics are understood and projected. The research into the endogeneization of important parameters in epidemiological models, however, has been purely concentrated on medical or biological applications. We propose a utility-based model for cultural contagion, which extends the class of so-called SIR models in epidemiology, and apply it first to the spread of Romanity in the ancient Greek world, through the dynamics of Roman names acquisition, and then to the spread of Christianism through Christian names acquisition. The dynamics of the transition from a pure Greek world to a Romanized world, explosive at the outset, appear to have been fundamentally driven by an intense adoption of Romanity, but combined with an equally intense return to traditional Greek traits. The transition from pagan to Christian names, on the other hand, saw less of a reversal effect.