Ancient Peru site older, much larger

A Peruvian site previously reported as the oldest city in the Americas actually is a much larger complex of as many as 20 cities with huge pyramids and sunken plazas sprawled over three river valleys, researchers report.

Construction started about 5,000 years ago — nearly 400 years before the first pyramid was built in Egypt — at a time when most people around the world were simple hunters and gatherers, a team from Northern Illinois University and Chicago's Field Museum reports in today's issue of the journal Nature.

The society and its people — known only as the Andeans — persisted in virtually the same form for 1,200 years before they were overrun by more warlike neighbors. That is the longest time any known ancient civilization survived, according to archaeologist Jonathan Haas of the Field, who led the expedition.

The results greatly expand understanding of how complex states began in the Americas.

"We are seeing the emergence of centralized decision-making, government and religion out of pristine conditions," Haas said. "They were not following a pattern established by someone else. They were developing it on their own. An Andean culture was being invented in this area."

Haas said people always have thought the Americas were behind Europe, Africa and Asia in terms of developing civilizations. The new dates for the region show the two worlds developed more or less simultaneously.

The findings also are overturning the previous belief that South American civilization was based in coastal cities supported by fishing. Instead, Andean society seems to have been built primarily on cotton farming and trade, supported by fishing villages.

"There wasn't anything like this in the world as far as I can tell," Haas said.

The first city to be discovered, Caral in the Supe River Valley, about 120 miles north of Lima, lay virtually ignored for more than 100 years after its discovery, despite its nearly 100-foot-tall pyramids. It had no golden or jeweled artifacts, no pottery shards with which to date it, and no art or writing to indicate its origins.

It was not until Haas' team first reported radiocarbon dates for the site three years ago that scientists appreciated its antiquity. Those dates indicated that Caral was built about 2600 B.C., much earlier than thought possible.

A new series of dates from the Supe River Valley, as well as the nearby Pativilca and Fortaleza valleys, show construction began even earlier, about 3000 B.C.

The driving force may well have been the Humboldt Current, a broad band of cold water rich in marine life, which served as a valuable food source.

But the climate turned much drier beginning about 3100 B.C., eliminating naturally growing fruits and vegetables that villagers relied on to supplement their diet of fish. They began looking inland for new food sources, Haas said.

"They figured out that if you take water out of the rivers and put it on desert land, the desert blooms and becomes very productive," he said. In the Norte Chico region, they could do so by hand-digging short canals.

They grew guava, beans, peppers and fruits — but not the corn or potatoes that researchers previously believed necessary to support a large population. But their most important crop was cotton, which was traded to coastal villagers to make fishing nets.

Andeans were peaceful. "They didn't fight with each other, and nobody else was big enough to fight with them," Haas said.

But beginning about 1800 B.C., possibly because the soil began to lose its productivity, new buildings and monuments got smaller and the big cities began to decline. New, larger cities appeared north and south of Norte Chico.

Warfare eventually began, and Norte Chico was conquered and abandoned.

The only occupants today are scattered farmers.