Strong El Nino episodes were so rare that relatively few people witnessed a truly catastrophic incident during their lifetimes. In a society where life expectancy was twenty-five to thirty-five years, generational memories were short. Great El Nino soon became remote happenings, almost beyond recollection except as near-mythic catastrophes recalled in oral traditions. The Moche lived in a uniform, usually reliable environment, with only drought as a common hazard. They built an elaborate, top-heavy society on this shakiest of foundations. Over many centuries, the coastal valley populations steadily rose, far beyond the natural carrying capacity of the and environment, until the only way to feed everyone was through massive, highly organized irrigation systems that used every drop of water that cascaded downstream during the spring mountain thaw. The warrior priests held the reins of power because they could deploy thousands of villagers to build and maintain some of the most intensive irrigation works ever built in the ancient world. But their tight hold on power was transitory, because their inflexible beliefs and insistence on absolutely centralized government left them at the mercy of powerful environmental forces. They had no long-term strategy against a phenomenon as maverick as El Nino.

The Moche's roots lay deep in the ancient cultures that had flourished for millennia along the Pacific coast of Peru. For thousands of years, small fishing and foraging groups settled at the mouths of dry coastal river valleys. They lived off the bountiful anchovy shoals that fed close inshore. In years when Pacific waters warmed up and the anchovy left for new feeding grounds, the people simply consumed other foods, such as shellfish and the winter fog-nourished wild plants that grew in dense clumps in river valleys close to the ocean. The ancient coastal people had such a variety of foods to live on that many groups stayed in one place for months on end. Theirs was a flexible, egalitarian society, with a reasonably ample supply of alternative foods to fall back on if the fishery failed or torrential rains came. Although some settlements were larger and more permanent, their total population was but a few thousand, partly because they lacked cotton for nets and lines and hollow gourds to serve as net floats, critical innovations for fishing on a large scale.

Population densities even in the most favorable areas were sufficiently low to allow for a degree of mobility, while stands of wild plant foods had not yet been overexploited. For many centuries, most groups lived in foggy zones close to the Pacific, where such foods were to be found. By 2000 B.C., many had moved. They still gathered plant foods but also relied on domesticated plants such as squashes and beans grown on river valley floors.

Today we take cotton for granted. The Andeans not only domesticated fine-quality, long-stranded cotton but made their mountain and lowland homeland a crucible of agricultural innovation, developing many different strains. Cotton soon became a staple of coastal society, used for fishing nets and lines and as a substitute for textiles made of cactus and grass fiber. Coastal communities discovered that cotton could be grown successfully in low-lying warm environments, and they developed a lucrative trade in fabric with the mountain highlands. This may have been why they opened up large areas of desert valley land to irrigation when many families and neighboring villages joined together to develop small-scale water control works. By 1800 B.C., as Egypt was recovering from political chaos, some Andean north-coast settlements boasted between one thousand and three thousand inhabitants living off a combination of fishing and agriculture. Valley populations rose far above the natural carrying capacity of the desert as the Andeans used irrigation technology and new styles of leadership to feed much larger communities.

Under such circumstances, how does a society cope with a strong El Nino. Given the Andeans' short life expectancy, El Nino strategies must have resided in communal rather than individual memory. As the New Guinea anthropologist Roy Rappaport emphasized as long ago as 1971, religious rituals were vital in the communication and validation of information, especially in areas like the Peruvian coast where conditions could change within a few weeks and rapid, flexible responses were essential. Under these circumstances, individuals with spiritual authority play important roles in supervising food storage. Over the generations, distinctive ideologies developed that validated strong leadership and the complex relations between the living and spiritual worlds. The messages of these ideologies have come down to us on textiles.

The coastal people were expert weavers. The dry climate of the Peruvian coast has preserved cotton cloth well over two thousand years old, much of it dyed in at least 109 hues in several natural color categories. The weavers spelled out a simple ideology in symmetrical, angular motifs that persisted for centuries. Anthropomorphic figures, perhaps shamans in trance, appear with flowing hair or snakes dangling from their waists. Birds of prey, snarling felines, and twoheaded snakes hint at close ties with a mythic, supernatural world. When fresh and brightly colored, the cotton textiles vividly depicted the myths, themes, and spirit creatures that inhabited the cosmos. The textiles bore a straightforward message that forged close links between the living and the dead, between communities and their ancestors, who interceded with the beings that controlled the land, food supplies, and forces of nature.

The coastal world changed rapidly as each community became more sedentary, more closely tied to river valley lands. By 1000 B.C., the kin leaders of earlier centuries had parlayed their powers as intermediaries with the ancestors into new, powerful roles. The ablest of them became competitive, authoritarian chieftains, capable of marshaling hundreds of villagers to labor on impressive pyramids and mounds honoring the supernatural forces that controlled the Andean world. During the quiet months of the farming year, teams of kin-group members labored to build such structures of rubble and adobe, some of which would endure for more than three thousand years. The Salinas de Chao pyramid on the north coast stands more than twenty-four meters high, a dwarf by the standards of Egypt's Pyramids of Giza, but still an imposing structure. The foundations of Moche civilization stemmed from these earlier cultural traditions, according to which shaman-rulers commanded by virtue of their control over the supernatural world.

The Moche state, named after the small river valley where it began, coalesced out of smaller valley kingdoms at about the time of Christ. The new supreme rulers took all the reins of power into their hands as they crafted a highly centralized state. Their capital, at Cerro Blanco in the heart of the Moche Valley, was a center of immense wealth and spiritual authority. The city's magnificent buildings sprawled around two enormous adobe huacas (pyramids). Nearby lay extensive cemeteries and the many workshops that produced ceremonial pottery and other artifacts for the elite.

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