Archaeologists used radiocarbon dating to chart the rise and fall of the little known culture, which reigned over three valleys north of Lima.

The society, whose heyday ran from 3000 to 1800BC, built ceremonial pyramids and complex irrigation systems.

The find casts doubt on the idea that Andean civilisation began by the sea.

"The scale and sophistication of these sites is unheard of anywhere in the New World at this time," said Jonathan Haas, MacArthur Curator of Anthropology at the Field Museum, Chicago.

"The cultural pattern that emerged in this small area in the third millennium BC later established a foundation for 4,000 years of cultural florescence in other parts of the Andes."

The Norte Chico civilisation differs from all other early civilisations in being based on marine resources rather than the cultivation of grains, says Winifred Creamer at Northern Illinois University in DeKalb, US, Haas's wife and colleague.
Their study reveals new complexity, with sites along the rivers growing squash, beans and avocados, and irrigating fields to grow cotton, which they exchanged for fish from the coast.
Refuse shows that inland residents had a diet heavy in small fish such as anchovies, which were abundant along the coast, while the cotton provided the nets needed to catch them, says Creamer.
The sites were permanent communities marked by rectangular stone step pyramids, typically 100 metres by 90 metres at the base. They were built by carefully assembling stones and plastering them to form a smooth floor before adding the next layer. Each site also had a circular sunken plaza, typically 20 m to 40 m in diameter.