You probably didn’t know this, but for a long time, researchers have suspected that bird droppings may have helped nations like Peru dominate their regions in ancient times. Now science has confirmed that bird poop is, in fact, a kingmaker of sorts.

New research published in PLOS One provides chemical evidence that guano from offshore islands fertilized maize grown by the Chincha Kingdom as far back as 800 years ago, and possibly much earlier. All that is to say that researchers think there is a ton of credible evidence suggesting that an abundance of seabird poop supported these coastal civilizations’ agriculture, which, in turn, provided a ton of political leverage.

The Humboldt Current, a.k.a. the Peru Current, is an ocean current that flows along the western coast of South America. It’s cold and nutrient-rich, making it one of the most productive marine ecosystems on Earth. Fish thrive there, which of course means that seabirds thrive there, too.

On the rocky islands just off the coast of Peru and Chile, centuries worth of bird poop piled up and turned into natural fertilizer, where all that nitrogen-rich material turned into an agricultural gold mine.

Dr. Jacob Bongers of the University of Sydney analyzed maize kernels recovered from tombs in the Chincha Valley. The crops contained elevated nitrogen levels and isotope ratios strongly associated with seabird guano. Combined with earlier archaeological evidence, like art depicting seabirds, fish, and sprouting maize, the chemical data confirms large-scale fertilizer use fueled by nitrogen-rich bird poop.

By at least 1250 CE, the Chincha were sailing 25 kilometers offshore to harvest guano, returning with loads to enrich their fields. The practice quickly became vital to their economy and culture as they exported surplus fertilizer via llama caravans, generating an incredible wealth.

As the Inca rose and crushed any other neighboring civilization that dared threaten them, the Chincha survived. Historical accounts suggest that the eventual incorporation into the Inca Empire wasn’t achieved through conquest but rather through negotiation. Access to all that rich, rich fertilizer, fueled by bird poop, might be the reason. They controlled the fertilizer; they controlled food production.

The Inca, recognizing how important this fertilizer was, reportedly banned island visits during seabird breeding seasons, a policy the researchers now consider an early example of conservation that demonstrates early civilizations’ understanding of life’s interconnectedness.

Of course, as they are wont to do, Europeans would later strip these islands for fertilizer and gunpowder, triggering global trade and starting wars, but long before industrial agriculture made a mess of indigenous civilizations, there was at least one group that understood that bird poop has a ton of value beyond a little bit of luck should you get pooped on.