Lots of llama droppings helped the ancient Inca build the largest empire ever to exist in the Americas, according to a new study.
Human populations took off and developed into complex societies in the Andes by switching from hunter-gathering to agriculture centered on maize, according to the research published in the June issue of the journal Antiquity. llama poop helped fertilize that crucial crop.
"This leap occurred 2,700 years ago and was made possible by a huge availability of animal excrement. Organic fertilizers enabled corn to be cultivated at very high altitudes, allowing the Inca to settle and flourish," Alex Chepstow-Lusty, a palaeoecologist from the French Institute for Andean Studies in Lima, Peru, told Discovery News.
The Inca ruled the largest empire on Earth -- stretching from the present-day southern border of Colombia to central Chile -- by the time their last emperor, Atahualpa, was executed by Spanish conquistadors in 1533.
Because the Inca language has no written form -- it has long been considered the only major Bronze Age civilization without a written language -- and due to the destruction of their heritage by the Spanish, the details of their meteoric rise have remained a mystery.
Chepstow-Lusty found reliable witnesses to reconstruct the "extraordinary plant-breeding event" which might be at the basis of the Inca Empire. These were pollen and mites buried in layers of mud on the floor of Lake Marcacocha in the Cuzco region of the Peruvian Andes, where Machu Picchu sits.
Similar to the rings in the trunk of a tree, each layer of sediment represents a fixed period of time. Taking a 6.3-meter (20.6 foot)-long sediment core from the lake bottom, Chepstow-Lusty investigated and radiocarbon-dated organic material from six layers, basically analyzing a 4,200-year-old sediment record.
The researcher found that maize pollen appears for the first time in the lake muds around 700 B.C., showing that the cereal could be cultivated at high altitudes of at least 3,350 meters (10,990 feet) above sea level.
Until then, Andean people were eating potatoes and quinoa, a grain-like plant similar to spinach which is very protein-rich.
According to Graham Thiele, an Andean agriculture specialist at the International Potato Center in Lima, maize indeed made a difference. More energy-dense than potato, it could be stored for much longer and was easier to transport.
"This really matters where there are no flat roads and wheeled vehicles and everything has to be carried on the back of a man or llama," Thiele told Discovery News.
"In addition, maize is more suitable for accumulation in elite controlled stores, and would have supported rent extraction by the emergent Wari and Inca elites. So maize trumps potato on transportability, storage and suitability for paying tribute," he said.
The lake sediment core also revealed that the highest abundance of oribatid mites, which eat animal dung, corresponded with the first appearance of maize.
This would show that, although corn was introduced to South America about 5,000 years ago, it reached the inhospitable Andes only with the help of llama herds. Located next to an ancient trade route between the jungle and the mountains, Marcaccocha was an ideal stop for llamas transporting goods.
"They used the pasture next to lake where they defecated communally. This was food for the mites, but also provided fertilizer which was easily collected and necessary for the maize to grow," Chepstow-Lusty said.
A brief period of warming between two major droughts also helped in growing maize at high altitudes.
"The Marcacocha record shows that a series of droughts associated with temperature increases, corresponding with major societal changes, occurred approximately every 500 years after 700 B.C.," Chepstow-Lusty said.
From 1100 A.D., the warming was sustained for at least five centuries, allowing the growth of the biggest Empire in the western hemisphere and lasting beyond the arrival of the Spanish in 1532 A.D.