The Supe Valley stretches eastward from the Pacific coastline and up the slopes of the Andes. Caral has some of the largest buildings of all the sites discovered in the valley; the largest platform mound of Caral is approximately the length of two football fields, nearly as wide, and five stories high.
The site also has a variety of apartment-like buildings, whose residential nature was indicated by the trash found inside. Other buildings at the site may have been used for ceremonial or administrative purposes, according to Science. Some of the architecture at Caral, such as two sunken circular plazas at the center of the site, is also typical of many younger sites that have been discovered in South America.
Haas said the radiocarbon dating offers greater insight into the ancient settlement. "Certain structures at Caral are common in the Andes, but now we know that these are some of the first. It's like saying, 'We're looking at the first Christian church,' " Haas said.
Research indicates that Caral's inhabitants used irrigation to cultivate a variety of plants, but no grains. "The planning that irrigation requires and the large amount of labor needed to build the city both imply that Caral was a state with a powerful government," the scientists concluded.
How such a powerful irrigation structure arose in the first place raises interesting questions, Creamer said. Researchers have long assumed that most complex societies cultivated some type of grain, which can be stored in large amounts and exchanged for work.
"We assume that providing a surplus of food is one of the first ways of concentrating wealth," she said. "One of the really intriguing aspects of our research is that there wasn't a product like corn in the Supe valley, but they still managed to develop in this complex way."
Creamer speculates that the citizens of the Supe Valley cities may have used an alternative type of food "currency," such as dried fish. Although economic systems based on corn have been extremely common worldwide, dried fish may have worked well enough for the several hundred years before corn was available, she noted.
The scientists say more work is needed to solve this mystery and other questions about Caral and the other sites in the Supe Valley, such as whether they were inhabited at the same time.
In fact, most of the Supe Valley sites have yet to be studied thoroughly, according to Creamer. Part of the reason they have received little attention, she explained, is because the sites, when discovered, appeared to lack many of the typical artifacts sought by archeologists and museum curators. The area's remote location is also a factor. Even today, the valley has no paved roads, electricity, or a public water system.
The research on Caral was funded by the National Geographic Society, the Istituto Nacional del Cultura of Peru, the Universidad Nacional Mayor de San Marcos, the National Museum of Natural History, and Northern Illinois University.
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