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The El Niño Effect Volume 54 Number 5, September/October 2001
by Colleen P. Popson

[image] Mollusk shells can track changes in El Niño. ( Johnson) [LARGER IMAGE]

Researchers analyzing mollusk shells recovered from middens along the Peruvian coast believe they have found a link between the abandonment of early centers in the region and El Niño, the oceanic and atmospheric condition that causes rainfall and flooding along the Pacific coast every three to seven years. Because mollusks are sensitive to temperature change, they can be used to track changes in the frequency of El Niño over time.

Construction of monumental ceremonial centers on the Peruvian coast began during the third millennium B.C. These centers were abandoned by 500 B.C., a period that coincides with an increase in El Niño frequency. In an environment already marked by climatic extremes, the inhabitants of these sites may not have been adequately prepared for El Niño's intensified repeat performances.

Although the researchers don't suggest the El Niño phenomenon was a primary cause for the demise of sites in the area, they find the concurrence of major cultural and environmental change during this period on the Peruvian coast intriguing.

"It could be coincidence, but that seems highly unlikely," says lead author Dan Sandweiss of the University of Maine Department of Anthropology and Institute of Quaternary and Climate Studies. "Changes in El Niño must have been a strong motivating force."

© 2001 by the Archaeological Institute of America