The Surprising Secret Behind an Ancient Andean Kingdom’s Rise

Seabird guano fertilization boosted maize production in ancient Peru, fueling Chincha wealth, trade networks, and strategic Inca alliances.

New archaeological findings show that seabird guano—nutrient-rich bird droppings—was not simply a farming aid but a foundation of economic and political power in ancient Peru. By dramatically improving corn yields, it may have played a central role in the emergence of the Chincha Kingdom as one of the most powerful and prosperous societies before the Inca.

Dr. Jacob Bongers, a digital archaeologist at the University of Sydney and Visiting Research Fellow at the Australian Museum Research Institute, said the research reveals how something as unassuming as bird droppings could shape entire civilizations in the Andes.

“Seabird guano may seem trivial, yet our study suggests this potent resource could have significantly contributed to sociopolitical and economic change in the Peruvian Andes,” Dr. Bongers said.

“Guano dramatically boosted the production of maize (corn), and this agricultural surplus crucially helped fuel the Chincha Kingdom’s economy, driving their trade, wealth, population growth, and regional influence, and shaped their strategic alliance with the Inca Empire. In ancient Andean cultures, fertilizer was power.”

Ancient Fertilizer-Powered Chincha Prosperity

The study, published in PLOS One, examined biochemical markers in 35 maize samples recovered from burial tombs in the Chincha Valley, which was once home to an estimated 100,000 people and a major coastal political center.

Laboratory testing found unusually high nitrogen concentrations in the maize, far exceeding what local soils would naturally provide. This is strong evidence that farmers enriched their crops with seabird guano, which contains elevated nitrogen levels because seabirds feed on marine life.

“The guano was most likely harvested from the nearby Chincha Islands, renowned for their abundant and high-quality guano deposits,” Dr. Bongers said. “Colonial‑era writings we studied report that communities across coastal Peru and northern Chile sailed to several nearby islands on rafts to collect seabird droppings for fertilization.”

Chemical Evidence Confirms Guano Fertilization

Beyond chemical testing, the team reviewed artwork from the region that depicts seabirds, fish, and sprouting maize together on textiles, ceramics, pottery, wall carvings, and paintings. These images provide additional evidence that seabirds and maize were deeply intertwined in daily life and belief systems.

“Together, the chemical and material evidence we studied confirms earlier scholarship showing that guano was deliberately collected and used as a fertilizer,” Dr. Bongers said. “But it also points to a deeper cultural significance, suggesting people recognized the exceptional power of this fertilizer and actively celebrated, protected, and even ritualized the vital relationship between seabirds and agriculture.”

Dr. Emily Milton, a postdoctoral fellow at the Smithsonian Institution in Washington, D.C., emphasized the importance of combining scientific data with historical sources.

“The historical records documenting how bird guano was applied to maize fields helped us interpret the chemical data and understand the regional importance of this practice,” she said. “Our work extends the known geographic extent of guano fertilization, echoing recent findings in northern Chile, and suggests soil management began at least around 800 years ago in Peru.”

Guano in Art, Ritual, and Historical Records

Agriculture along Peru’s coastline has always been difficult. It is one of the driest regions on Earth, and even irrigated farmland quickly becomes depleted of nutrients. Transporting guano from offshore islands offered farmers a powerful and renewable fertilizer, allowing communities in the Chincha Valley to grow maize, one of the most important staple crops in the Americas, in large quantities.

Reliable harvests created a surplus that sustained merchants, farmers, and fisherfolk, and helped turn the Chincha into dominant traders along the coast.

“We know the Chincha were extraordinarily wealthy and one of the most powerful coastal societies of their time. But what underpinned that prosperity? Previous research often pointed to spondylus shells, the spiny oyster, as the key driver of merchant wealth,” Dr. Bongers said.

Desert Agriculture and Coastal Trade Networks

“Our evidence suggests guano was central to the Chincha Kingdom’s success, with the Chincha’s maritime knowledge and access to the Chincha Islands likely reframing their strategic importance in the region.”

The Inca, who later built the largest native empire in the Americas before European contact, were based in the Andean highlands. They valued maize highly, using it to brew ceremonial fermented beer known as ‘chicha.’ However, they struggled to cultivate large amounts of maize in high-altitude environments and did not have seafaring capabilities.

“Guano was a highly sought-after resource the Incas would have wanted access to, playing an important role in the diplomatic arrangements between the Inca and the Chincha communities,” Dr. Bongers said.

“It expanded Chincha’s agricultural productivity and mercantile influence, leading to exchanges of resources and power.”

Guano Shaped Inca–Chincha Alliances

Coauthor Dr. Jo Osborn at Texas A&M University said the findings challenge modern assumptions about wealth in the ancient Andes.

“The true power of the Chincha wasn’t just access to a resource; it was their mastery of a complex ecological system,” she said. “They possessed the traditional knowledge to see the connection between marine and terrestrial life, and they turned that knowledge into the agricultural surplus that built their kingdom. Their art celebrates this connection, showing us that their power was rooted in ecological wisdom, not just gold or silver.”

The research also builds on Dr. Bongers’ earlier work at the Band of Holes, located just south of the Chincha Valley, which he has proposed was an ancient marketplace constructed by the Chincha Kingdom.

“This research adds another layer to our understanding of how the Chincha, and potentially other coastal communities, used resources, trade, and agriculture to expand their influence in the pre-Hispanic era,” Dr. Bongers said.

Reference: “Seabirds shaped the expansion of pre-Inca society in Peru” by Jacob L. Bongers, Emily B. P. Milton, Jo Osborn, Dorothée G. Drucker, Joshua R. Robinson and Beth K. Scaffidi, 11 February 2026, PLOS ONE.
DOI: 10.1371/journal.pone.0341263

Funding for archaeological fieldwork and isotopic analyses of maize samples was provided to JLB by the National Science Foundation Graduate Research Fellowship Program, the Society of Fellows at Boston University, the Ford Foundation Fellowship Program, the National Geographic Young Explorers Grant Program, and the Sigma Xi Grants-in-Aid Research Program.

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