Llama Poop: A Scientific Method to Track the Rise and Fall of the Inca Empire

While in history class, we learned about the past of South American empires, one of them being the Inca Empire, and how we use different methods to historically investigate their rise and fall. The Inca Empire was primarily located in the Andes and stretched from the south of Colombia to present day Chile and out towards Bolivia.  The Andes is a diverse and long mountain range, and over many years the Incas developed and built intricate roads and paths to get to and from cities and towns. Travellers and merchants of the Inca empire would often travel to the ancient city of Ollantaytambo and pass by Lake Marcacocha on the way. Llamas were commonly used during these trips as a mode of transportation of goods and food used by the Incas. These llamas would then drink, rest, eat and defecate by the lake. The poop of Llamas was known to be a fertilizer for their crops, mainly maize, but it was also consumed by other organisms.

Greetings from Machu Picchu © Geriant Rowland CC BY-NC 2.0

Scientists have always found it difficult to accurately track and understand the rise, fall and disruption of empires. However, in recent years, a fungus known as Sporormiella has shed some light on the blurry past of South America. Sporormiella lives on herbivore dung and is commonly used to track the populations of plant eaters. Typically, a drop in Sporormiella numbers means the extinction of a species. However, in the case of the Inca Empire, this correlation is not technically true. When the Inca Empire was defeated, llamas were no longer used as much as before – however, they did not die off. Therefore, in this instance, Sporormiella can be thought of as relating to the proximity of the animal to the water with levels changing during dryer seasons as the lake shrinks in diameter. Alex Chepstow-Lusty writes in the Journal of Archaeological Science that Sporormiella is a better water level and environmental indicator than a species tracker.

There is another poop-eating organism known as mites which is a group of insects in the arthropod phylum. When the travellers, alongside their llamas, passed by the lake of Marcacocha there was a notable amount of Inca poop that was excreted in the lake and neighbouring grasslands. As a result, the mites that lived in the lake increased in number during the years of 1438 C.E. to 1533 C.E when the Inca Empire ruled the Andes. When mites die they sink to the bottom and reside in the layers of the lake. They can be counted by looking at the different layers of the sedimentary cores. It was found that the mites followed the historical account of the defeat of the Empire and its rise. When there were more llamas passing through Marcacocha, the number of mites increased.

It is quite incredible how we are able to use science and apply it to a historical investigation. This is only one of many examples in which science has intertwined with other disciplines to increase our understanding about the world.

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