In the Andean foothills of Peru, not far from the Pacific coast, archaeologists have found what they say is evidence for the earliest known irrigated agriculture in the Americas.
An analysis of four derelict canals, filled with silt and buried deep under sediments, showed that they were used to water cultivated fields 5,400 years ago, in one case possibly as early as 6,700 years ago, archaeologists reported in a recent issue of The Proceedings of the National Academy of Sciences.
Other scholars hailed the discovery as adding a new dimension to understanding the origins of civilization in the Andes. The canals are seen as the long-sought proof that irrigation technology was critical to the development of the earliest Peruvian civilization, one of the few major cultures in the ancient world to rise independent of outside influence.
It was assumed that by 4,000 years ago, perhaps 1,000 years earlier, large-scale irrigation farming was well under way in Peru, as suggested by the indirect evidence of urban ruins of increasing size and architectural distinction. Their growth presumably depended on irrigation in the arid valleys and hills descending to coastal Peru. But the telling evidence of the canals had been missing.
Then Tom D. Dillehay, an archaeologist at Vanderbilt University, started nosing around the Zaña Valley, about 40 miles from the ocean and more than 300 miles north of Lima.
On the south side of the Nanchoc River, he and his team uncovered traces of the four canals, narrow and shallow, lined with stones and pebbles, extending from less than a mile to more than two miles in length. The canals ran near remains of houses, buried agricultural furrows, stone hoes and charred plants, including cotton, wild plums, beans and squash.