Papua New Guinea (PNG) is the most linguistically diverse nation on the planet, but also one of the world's least developed countries. What accounts for that heterogeneity? Can this explain weak development outcomes, or do other factors â€“ such as geographical constraints or historical legacies â€“ play the more significant role? For this paper, we assembled a unique database showing the extent of linguistic diversity in PNG's 85 rural districts in order to investigate its impact on human development (measured using child mortality and school attendance). We find some evidence of a relationship between linguistic diversity and development, but a careful reading of PNG's history suggests that it would be mistaken to interpret this as evidence of heterogeneity impeding development. Whereas some economists see linguistic diversity as having a linear relationship with the time-distance since human settlement, we argue that shifting crop cultivation technologies, warfare, disease and environmental convulsions â€“ in tandem with time-depth â€“ offer the better explanation. We also test and reject the fashionable hypothesis that â€˜pre-colonial hierarchyâ€™ has a strong and enduring influence over contemporary development outcomes.