New archaeological research suggests that seabird guano, the nutrient-rich bird droppings, may have played a major role in transforming ancient Peruvian agriculture and helped the Chincha kingdom emerge as one of the most prosperous and influential societies before the Incas.
The study’s lead author, Dr Jacob Bongarth, a digital archaeologist at the University of Sydney and a visiting fellow at the Australian Museum Institute, said the findings reveal the surprisingly powerful influence bird droppings had on Andean civilization.
“Although seabird guano may seem trivial, our study suggests that this powerful resource may have contributed significantly to sociopolitical and economic changes in the Peruvian Andes,” Dr. Bongers said.
“Guano dramatically increased the production of maize (maize), and this agricultural surplus served crucially to stimulate the economy of the Chincha Kingdom, fostering trade, wealth, population growth, regional influence, and forming a strategic alliance with the Inca Empire.
“In ancient Andean cultures, fertilizer was power.”
Ancient fertilizer revealed by scientific analysis
This study pro swanexamined biochemical markers in 35 maize samples recovered from burial graves in the Chincha Valley. The area once supported a strong coastal community with an estimated population of approximately 100,000 people.
Laboratory analysis showed that corn had very high nitrogen levels. These levels far exceeded what the surrounding soil could naturally produce. The results strongly suggest that crops were fertilized with nitrogen-rich seabird guano because seabirds feed on marine life.
“The guano was most likely extracted from the nearby Chincha Islands, which are famous for their rich and high-quality guano deposits,” Dr Bongers said. “The colonial texts we studied report that communities in coastal Peru and northern Chile would sail to several nearby islands on rafts to collect seabird droppings for fertilizer.”
The team also studied archaeological artefacts in the area. Images of seabirds, fish, and sprouted corn appear together on textiles, pottery, pottery, wall carvings, and paintings. These depictions provide further evidence that seabirds and corn had deep cultural significance in these societies.
“Taken together, the chemical and physical evidence we studied supports previous research showing that guano was intentionally collected and used as fertilizer,” Dr. Bongers said. “But it also points to a deeper cultural significance, suggesting that people recognized the extraordinary power of this fertilizer and actively celebrated, protected, and even ritualized the important relationship between seabirds and agriculture.”
Dr. Emily Milton, a postdoctoral fellow at the Smithsonian Institution in Washington, D.C., said combining multiple research approaches is key to understanding this practice.
“Historical records documenting how bird guano was applied to corn fields helped us interpret chemical data and understand the regional significance of this practice,” she said. “Our study expands the known geographic range of guano fertilization, mirrors recent discoveries in northern Chile, and suggests that soil management began in Peru at least about 800 years ago.”
Farming in one of the driest places on earth
Agriculture along the Peruvian coast has always been difficult, as the region has some of the driest environments on earth. Even irrigated farmland loses nutrients quickly. Guano shipped from offshore islands provided farmers with a powerful, renewable fertilizer that made it possible to grow large quantities of corn in the Chincha Valley.
Corn was one of the most important staple crops in the Americas. The ability to grow it in abundance created an agricultural surplus that supported merchants, farmers, and fishermen. This prosperity led the Chincha to become major coastal traders.
“We know that the Chincha were extremely wealthy and one of the most powerful coastal societies of their time. But what underpinned their prosperity? Previous research has often pointed to the vertebral shell, the spiny oyster, as the main driver of merchant wealth,” Dr. Bongers said.
“Our evidence suggests that guano was central to the success of the Chincha Kingdom, and Chincha maritime knowledge and access to the Chincha Islands likely reshaped its strategic importance in the region.”
Guano, trade, and relations with the Inca Empire
Based in the high Andes, the Inca civilization established the largest indigenous empire in the Americas before the arrival of Europeans. Corn was of great cultural importance to the Incas and was used to make a ceremonial fermented beer called “chicha.” However, it was difficult to grow large amounts of corn in the highlands, and the Incas lacked navigational skills.
“Guano was a highly sought-after resource that the Incas wanted access to, and it played an important role in diplomatic agreements between the Inca and Chincha communities,” Dr. Bongars said.
“This expanded Chincha’s agricultural productivity and commercial influence, leading to exchanges of resources and power.”
Ecological knowledge behind Chincha’s prosperity
Co-author Dr. Joe Osborn of Texas A&M University said the discovery prompts a broader rethinking of how wealth and power functioned in the ancient Andes.
“Chincha’s real power was not just access to resources, but mastery of complex ecosystems,” she says. “They had traditional knowledge of the connections between marine and terrestrial life and turned that knowledge into agricultural surpluses that built their kingdoms. Their art celebrates this connection and shows us that their power was rooted in ecological wisdom, not just gold and silver.”
This research also builds on Dr. Bongers’ previous work on the Band of Holes, located just south of the Chincha Valley. He suggests that the site may have functioned as an ancient market run by the Chincha Kingdom.
“This study adds a new layer to our understanding of how the Chincha, and perhaps other coastal communities, used resources, trade, and agriculture to expand their influence in pre-Hispanic times,” Dr. Bongers said.
Funding for the archaeological fieldwork and isotopic analysis of corn samples was provided to JLB by the National Science Foundation Graduate Research Fellowship Program (DGE-1144087), the Boston University Society of Fellows, the Ford Foundation Fellowship Program, the National Geographic Young Explorers Grant Program (9347-13), and the Sigma Xi Grants-in-Aid Research Program. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
