What we're learning from Caral is going to rewrite the way we think about the development of early Andean civilisation

Jonathan Haas, Field Museum in Chicago

This date pushes back the emergence of the first complex society in the New World by nearly 800 years.

And it suggests that the people behind the project were advanced enough to organise the labour needed to create the architectural wonder of the day.

Caral is one of 18 sites in central Peru's Supe Valley, which stretches eastward from the Pacific coastline, up the slopes of the Andes.

Earth pyramids

All the inland settlements once had architecture on a grand scale, including the six huge platform mounds seen at Caral.

Because of its size and complexity, archaeologists had thought Caral was built about 1,500 BC.

But carbon dating of plant samples found at the site add another 1,000 years or so to this figure.

The pyramids are buried under a layer of windblown and sand

That puts Caral in the same period as the great pyramids of Egypt, and long before the huge stone structures of Mexico.

"What we're learning from Caral is going to rewrite the way we think about the development of early Andean civilisation," said study leader Jonathan Haas of the Field Museum in Chicago, US.

The Peruvian-American archaeological team says the pyramids and irrigation system show an organised society in which masses of people were paid, or compelled, to work on centralised projects.

This suggests that power and wealth were held by an elite group at a time when, in most of the Americas, people were still hunting and gathering in much smaller communities.

No pots

"The size of a structure is really an indication of power," said Haas.

"It means that leaders of the society were able to get their followers to do lots of work."

What is surprising to archaeologists is that the city was created by a society that had yet to invent pottery or cultivate grain.

Its people grew peppers, beans, avocadoes and potatoes - all of which they roasted, having no pots to boil them in.

They also ate lots of anchovies, which may have been used in dried form as a kind of currency, as grain was later.

The research is published in the journal Science.