Inca culture spread from Andes after manure from llama herds provided fertiliser for corn crops at high altitude.
The Incas may have created the biggest empire in the Americas and built Machu Picchu, among other wonders, thanks to a previously overlooked ingredient: llama dung.
Manure from llama herds provided fertiliser which enabled corn to be cultivated at very high altitudes, allowing the Inca civilisation to flourish in the Andes and conquer much of South America, according to research.
The “extraordinary plant-breeding event” some 2 700 years ago transformed the region’s political economy and enabled the Incas to emerge centuries later, said Alex Chepstow-Lusty, of the French Institute of Andean Studies in Lima.
“This widespread shift to agriculture and societal development was only possible with an extra ingredient—organic fertilisers on a vast scale.” The study, published in the latest edition of the journal Antiquity, found corn pollen in the mud of Marcacocha lake, near Ollantayambo, showing the cereal could be grown at least 3 350m above sea level.
“From 2 700 years ago we can see the beginnings of agriculture in the first appearance of formal field systems, the introduction of maize, and weeding as common practice,” said Chepstow-Lusty, a British palaeo-ecologist.
The breakthrough reduced dependence on quinoa, a grain-like plant similar to spinach, and boosted calorie intake, leading to a decline in the growth and consumption of wild quinoa “and the origins of the Inca empire”.
Corn was introduced to South America from Mexico about 5 000 years ago but did not scale the Andes until humans enriched the soil with help from llama herds. “They defecate communally so it is easily gathered,” said Chepstow-Lusty.
He made the discovery by studying the lake mud’s abundant mites, which eat animal dung. Climate change, in the form of warmer temperatures, also helped Inca society to evolve by making it easier to cultivate corn at high altitudes.
The Incas also used llama manure as fuel to cook and make ceramics. Garcilaso de la Vega, an early Spanish chronicler, noted that farmers in the Cuzco valley also used human manure to fertilise crops.
In the 12th century the Incas were just one of several tribes in what is today Peru but by the 15th century they boasted an empire encompassing parts of modern-day Argentina, Boliva, Chile and Ecuador. The glory ended when Spanish conquistadores defeated the Incas and killed the emperor, Atahualpa, in 1533.
The citadel of Machu Picchu was abandoned and largely unknown to the outside world until an American explorer, Hiram Bingham, “rediscovered” it in July 1911. The anniversary is expected to boost the already large numbers of tourists who visit the site.—guardian.co.uk