Half buried in the deserts of Peru's central coast, the ruins of Caral have been dubbed America's first city. Dated to about 2627 B.C.E., it preceded all other known New World settlements by nearly 800 years. But Caral, it turns out, was no one-hit wonder. New radiocarbon dates from sites in adjoining river valleys expands this early civilization from one city to 20. The discovery, reported in the 22 December issue of Nature, sheds new light on the emergence of the first settled agricultural society in the New World.
Researchers led by anthropologist Jonathan Haas of Chicago's Field Museum report many ruins in the Norte Chico region are very similar to Caral. Structures included monumental stone buildings, circular ceremonial plazas, and rectangular platform mounds. Short irrigation canals capable of watering large fields bordered every city. To establish the ages of the sites, the researchers analyzed organic materials from 13 of the 20 cities. When possible, they sampled the very materials used to construct the buildings--cane fibers woven into bags and filled with rock.
Nearly a third of the samples fell between 3200 and 2500 B.C.E., pointing to a sudden human population explosion. "There's a big group of sites arising at the same time," Haas says. "By 2200, about 18 sites are occupied at the same time." The fuel behind this phenomenal growth, the researchers say, was the adoption of agriculture. Although crops such as cotton and squash had been domesticated earlier on the continent, Haas says, "this marks the first time you see agriculture emerging as a full-time economy in the Americas."
Domesticated cotton, squash, avocado, and guava remains have all been found in the area. Yet evidence of a staple grain--a nutritional foundation of the world's other early civilizations--is missing. Instead, Peru's first urbanites may have roasted, chewed, and then spat out the tuberous root of a type of cane. Sardine remains in fossil feces indicate residents ate seafood as well.
Together with previous dates from the contemporary coastal site of Aspero, the findings point to a widespread trade network. Cotton fishing nets in maritime settlements 150 miles north, which lacked their own inland cities, suggest fishermen up and down the coast traded their catches for Norte Chico plant products. That prosperity, says Haas, translated into 1200 years of cultural dominance. "If you look at Andean civilization as a long story, it starts at Norte Chico and ends with the Inca in 1500."