Chemical analysis of ancient maize cobs reveals that the Chincha Kingdom harvested seabird guano as fertilizer from the 13th century onward. This nutrient-rich resource likely contributed to the kingdom's economic strength before its incorporation into the Inca Empire. Researchers highlight how access to guano provided a key advantage in agricultural productivity.
The Chincha Kingdom, which flourished between AD 1000 and 1400 in one of Peru's most productive coastal valleys, appears to have leveraged guano—a mix of seabird excrement, feathers, and carcasses—as a powerful fertilizer. Located just 25 kilometers from the Chincha Islands, home to colonies of Peruvian pelicans (Pelecanus thagus), Peruvian boobies (Sula variegata), and guanay cormorants (Leucocarbo bougainvilliorum), along with penguins and gulls, the kingdom transported this high-nitrogen material to inland fields.
Archaeological evidence comes from the analysis of 35 ancient maize cobs collected from 14 cemeteries in the Chincha valley. These cobs, possibly used as offerings for the dead, displayed unusually high nitrogen-15 isotope levels, indicating fertilization with seabird guano. To confirm this, researchers examined collagen from 11 seabird bones, including those from pelicans, boobies, cormorants, a gull, and a penguin, establishing a local isotopic baseline.
Jacob Bongers at the University of Sydney, who led the study with Emily Milton at the Smithsonian Institution, noted the significance: “Privileged access to a crucial resource is a pathway to power – which the Chincha Kingdom had in this case, and the Inca did not.” He added, “Social change may have arisen from a surprising source: bird poop. It’s a fascinating story.”
The findings, published in PLOS One (DOI: 10.1371/journal.pone.0341263), suggest guano use by at least 1250, as stated by Jo Osborn at Texas A&M University. Seabird imagery on Chincha textiles, ceramics, and architectural friezes underscores the cultural importance of these birds. While Inca use of guano is documented in colonial accounts, with strict controls and penalties for harming birds, this is the first firm evidence for the Chincha.
Dan Sandweiss at the University of Maine, not involved in the research, commented: “It makes a lot of sense that ancient Peruvians used guano as fertiliser... This Peruvian guano was the real stuff,” attributing its value to low rainfall preserving the nitrogen.