Pre-historic (i.e. before written language's in South America, before the Spanish Conquest in 1532) Peruvian civilizations were predicated on agriculture. The relatively dense population depended
on intensive cultivation for food, while the rulers of powerful empires like that of the Inca demanded a large agricultural surplus to underwrite their political apparatus. Successful agriculture, in turn, depended on climate. The Peruvian coast is an
exceptionally dry place, and coastal civilizations could only rise during pluvial (rainy) periods. Highland cultures, on the other hand, raised crops near their elevational and climatic limit (the altiplano, it should be remembered, is higher than most
Rocky Mountain peaks). Because of their dependence on cultivating crops in climatically sensitive areas, Peruvian civilizations rose and fell to the oscillations of climate.
In this figure, the accumulation record from Quelccaya is compared to
the archaeological record of Peruvian pre-history (the sequences presented here are based on pottery styles and other archaeological evidence). Because of a poorly understood mechanism, periods of wetness in the altiplano generally correspond to
periods of drought on the coast, while pluvial periods on the coast correspond to drought in the highlands. As the figure clearly demonstrates, highland cultures such as the Huari and Inca Empires flourished during highland pluvials, while coastal
cultures such as the Chimor flourished during highland droughts. As you can see, the Quelccaya ice cap provides not just vital information on Earth's climate history, but also valuable insight into Andean pre-history.
Thomas Andrews after Thompson (1992).
NOAA Paleoclimatology Program and INSTAAR, University of Colorado, Boulder
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