Newswise — Canals discovered in the Peruvian Andes dating back over 5,400 years offer long-sought proof that irrigation was at the heart of the development of one of the earth's first civilizations.
The discovery by Vanderbilt University anthropologist Tom Dillehay and his colleagues, Herbert Eling, Instituto Naciona de Anthropolotica e Historia in Coahulila, Mexico, and Jack Rossen, Ithaca College, was reported in the Nov. 22 issue of the Proceedings of the National Academy of Sciences.
The anthropologists discovered the canals in Peru's upper middle Zana Valley, approximately 60 kilometers east of the Pacific coast. Preliminary results indicate one of the canals is over 6,700 years old, while another has been confirmed to be over 5,400 years old. They are the oldest such canals yet discovered in South America.
"Peru is one of the few places on the planet where there was independent development of civilization. One of the signatures of the beginning of civilization and complex society is intensive agriculture, where you have not only crops but also irrigation technology," Dillehay, distinguished professor of anthropology and chair of the department, said. "That element—irrigation technology—was always missing in archaeological findings of early Andean civilization. We found it by looking farther up the valley away from the coastal plains and by excavating deeply."
Anthropologists had presumed that the canals that helped support early Andean civilization had lain closer to the surface and were hence destroyed by human activity and nature over time. Dillehay and his team found that the canals had not been destroyed but had been buried by sediment. The team made its initial discovery of the canal system in 1989 and has been working since to uncover the broader picture of the canals and the civilization that they supported.
"Our findings indicate that people were building these canals and creating artificial wetlands—essentially garden plots—in the Andes over 5,400 years ago," Dillehay said. "This was an important moment for this civilization as it established a codependency between the crops and the people, which allowed and encouraged larger groups of people to begin to settle down in one place.
"This type of agriculture also created leisure time, allowing people to do things such as crafts and to become involved in public ritual," Dillehay continued. "What you see in a civilization after they start cultivating food and domesticating animals are changes in social life."
The team uncovered four canals ranging in length from one to four kilometers. The canals are narrow, symmetric, shallow and U-shaped. They were lined with stones and small pebbles, and appear to be individually designed to take advantage of different periods of water availability. The canals were built along the edge of a terrace above a nearby stream and used gravity to deliver water downhill to the agricultural fields. A striking feature of the canals is that they are located on a very slight slope, indicating that their builders were able to engineer them to function hydraulically in a relatively sophisticated manner. All domestic sites found in the area lie within 2.5 kilometers of the canals and share tools, structures, dietary remains and other features, indicating they were part of the same society.
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Proceedings of the National Academy of Sciences (22-Nov-2005)