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Mite fossils show Incas' rise and fall

March 31, 2007|Thomas H. Maugh II | Times Staff Writer

An international team of archeologists has found a new way to trace the rise and fall of the Inca civilization -- the fossils of tiny soil-dwelling organisms called mites.

In the absence of written records, the mites may provide the most reliable way to document the Incas and other South American societies, said the study's leader, paleoecologist Alex J. Chepstow-Lusty of the University of Montpellier in France.

The mites feed on the droppings of llamas, the primary beast of burden in the region, in moist grasslands and pastures, and their chitinous shells are readily preserved in waterlogged sediments.

The team concluded that the number of mite fossils in a soil sample is related to the number of llamas that used the pasture, and thus to the population.

They studied core samples from the sacred lake Marcacocha in the Patacancha Valley of Peru, near Cuzco. The remnants of the lake lie within 50 yards of a major trade route that linked the Amazon forest to the east with the strategic Inca settlement of Ollantaytambo about eight miles downstream.

During the height of Inca civilization, Spanish records indicate, llama trains consisting of up to 1,000 animals used the trade route regularly, carrying coca leaves and other products.

The team reported this week in the Journal of Archaeological Science that they drilled an 8 1/4-yard core from the lake and measured mite concentrations at various levels, which were also dated accurately.

They found a marked increase in mite fossils as the Inca Empire expanded from Cuzco in the early 1400s -- toward the end of a period of warm temperatures known as the Medieval Warm Period.

A later, but very sudden, drop in the number of mites reflects the cataclysmic indigenous human population collapse with the arrival of the Spanish and their own domesticated animals. Historical accounts document that two-thirds of the llamas in the Cuzco region died of horrendous skin diseases.

When the Spanish introduced their own livestock onto the landscape in the 1600s, the frequency of fossils increased again.

In the early 1700s, the mites underwent another decline. This was not only the coldest part of the climatic period known as the Little Ice Age, but a plague was also ravaging the area, killing as many as 600 people a day in Cuzco.

Having validated the technique at Marcacocha, the team is preparing to employ it in areas where there is less historical documentation of settlement patterns.

"To get to grips with the nitty-gritty detail of human activity through history ... even the smallest and most mundane of animals, such as excrement-eating mites, can sometimes provide a window into the calamitous impact that the Europeans had when they settled in the New World," Chepstow-Lusty said.

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