A new archaeological study undertaken by researchers from the University of Sydney and Texas A&M University has revealed that seabird guano was instrumental in the rise of Southern Peru’s Chincha Kingdom 800 years ago.
Seabird guano, which is rich in phosphorous, nitrogen and potassium, is a fantastic soil fertiliser and is still used today to boost crop yields.
According to lead author Jacob Bongers, this ‘white gold’ not only supercharged agriculture in ancient Peru, it may have also sparked the rise of the Chincha Kingdom and allowed it to become one of the most prosperous and influential pre-Inca societies in South America.
“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,” he said. “In ancient Andean cultures, fertiliser was power.”
The Chincha Kingdom is named after the valley its peoples lived in. This 25km-long valley is somewhat of an oasis; surrounded by the Peruvian Coastal Desert - one of the driest areas on Earth - it’s the only place for hundreds of miles with reliable access to freshwater.
At the height of the Chincha Kingdom’s power 800 years ago, the valley was home to roughly 100,000 people.
Before they arrived at their guano-fuelled expansion conclusion, Bongers and co-author Jo Osborn analysed biochemical signatures in 35 maize samples recovered from burial tombs in the Chincha Valley.
These analyses revealed exceptionally high nitrogen levels in the maize - levels far beyond what they expected to see. This suggested the soil the maize was grown in was artificially fertilised, and the high nitrogen levels pointed Bongers and Osborn to a particularly potent, nitrogen-packed fertiliser, seabird guano.
“The guano was most likely harvested from the nearby Chincha Islands, renowned for their abundant and high-quality guano deposits,” 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 fertilisation.”
The Chincha Islands are home to Guanay cormorants, though the populations of these seabirds have declined by up to 90% in recent years due to climate change, bird flu, and overfishing of their food sources.
In the mid-19th century, when these islands became an international hub for guano mining, undisturbed deposits of droppings are said to have been up to 60m thick.
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As well as performing biochemical analyses, Bongers and Osborn examined regional artwork featuring seabirds, fish and sprouting maize. These artworks appeared on a variety of items, including textiles, ceramics and pottery, suggesting that seabirds and maize were very important to the Chincha people.
“The true power of the Chincha wasn’t just access to a resource; it was their mastery of a complex ecological system,” Osborn 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 Chincha Kingdom flourished in the Late Intermediate Period (900 AD - 1450 AD) before eventually disappearing in the mid-16th century, shortly after the Spanish conquest of Peru. Before its collapse, the kingdom fell under the dominion of the expanding Inca Empire, which is widely regarded as the ‘last chapter’ of thousands of years of Andean civilisations.
The study, undertaken by Bongers and Osborn, was published today in PLOS One: Seabirds shaped the expansion of pre-Inca society in Peru.
Top image: Chincha Valley. Credit: Jo Osborn
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