In places like coastal Peru, dry conditions preserved the nitrogen instead of washing it away, making the guano especially potent. Researchers say privileged access to this nutrient-rich fertiliser may have boosted agricultural output and economic power.

Credits: Unsplash; Author: Sam Badmaeva;

Scientists analysed 35 maize cobs from 14 cemeteries and compared them with isotopic data from 11 ancient seabird bones. The evidence suggests the Chincha Kingdom was harvesting guano from offshore islands by at least AD 1250. Historical records document Inca control of guano islands, but this provides firm archaeological evidence of earlier Chincha exploitation.