Oldest city in the Americas left a warning in clay 4,000 years ago, now we know what it says

On a dusty stretch of Peru’s central coast, clay walls in Caral show starving bodies, expectant mothers, and scenes of deep loss.

Archaeologists now read these scenes as a record of a climate catastrophe that forced one of the Americas’ earliest civilizations to change how it lived.

These murals come from new settlements that rose after the city of Caral, a major urban center in the Supe Valley, could no longer rely on its usual rains.

Faced with collapsing harvests about four millennia ago, its people shifted toward fresh towns near the sea and rivers, and they did so without clear signs of war.

Climate warning in Caral’s clay walls

An official Caral frieze, a raised band of sculpted wall decoration, shows starving adults in a lower row of figures.

Above them, a second register highlights young, thin dancers and large fish that allude to scarce food and fragile survival.

Higher still, a human shaped toad stretches its hands around a closed eyed face while a lightning bolt strikes its head.

Together the stacked images trace a story from death and hunger toward the long awaited return of water.

The work was led by Ruth Shady Solís, a Peruvian archaeologist who directs long term excavations across the Caral region.

Her research focuses on early Andean cities, trade networks, and the ways communities respond to environmental stress.

These temple walls stood in ceremonial rooms where people gathered to perform rituals, hear stories, and remember past disasters.

By carving hunger, lightning, and fertile bodies into mud plaster, the community turned lived trauma into a shared warning for future generations.

Leaving Caral without weapons

Farther up the Supe River, Caral itself was a planned city with stepped pyramids, sunken plazas, and dense housing.

Radiocarbon dating, a way to estimate age from radioactive carbon, places Caral’s monumental center between about 2600 and 2000 before the common era.

Archaeologists working at Peñico and Vichama see reused building styles but almost no weapons, fortification walls, or evidence of organized killing.

Instead of fighting over shrinking crops, families shifted toward fishing in the cold Pacific and farming along nearby river terraces.

New settlements kept familiar religious layouts with pyramids and sunken plazas, yet they anchored daily life closer to the sea and dependable groundwater.

Across the Atlantic and beyond, researchers studying cave deposits and lake mud cores describe a prolonged megadrought. That term refers to a decades-long period with unusually low rainfall that began near 4,200 years ago.

Trade, stories, and status

Peñico seems to have connected valley farms, coastal fisheries, and highland routes that stretched toward the Amazon.

Excavations there reveal monkey and macaw remains, tropical shells, and painted ceramics that point to long distance exchange.

Clay figures of men and women with decorated faces and hair suggest shared status across genders. Archaeologists think these figures stood in homes and ritual spaces to reinforce social roles.

Its plazas probably worked as markets where fish, cotton, squash, maize, and imported goods moved between neighbors and travelers. This steady flow of items from different regions would have eased the strain of poor harvests.

Carved conch shell trumpets called pututus appear in reliefs and as instruments, marking leaders who could call people together for announcements, rituals, or crisis meetings.

Music, architecture, and story packed walls all worked together to hold communities together while rivers shrank and winds dried the fields.

Connecting Caral’s walls with drought

Climate records from cave speleothems, mineral deposits that grow slowly from dripping water, ocean sediments, and dust layers show that rainfall patterns changed sharply.

Many of those records cluster around a shift near 4,200 years ago, when several regions became drier and more variable.

Ancient Mesopotamian texts and archaeological layers from the Akkadian Empire, the Indus cities, and parts of Syria point to abandoned fields, invasive dust storms, and disrupted trade around this time. 

Scholars continue to debate how much climate versus politics mattered in those collapses, a conversation that now draws on dozens of regional climate records and new excavations.

Caral’s people lived far from those empires, yet their move from the main city into coastal and inland satellites fits the same rough window of stress.

Instead of building out fortresses, they built out harbors, canals, terraces, and memory laden temples that reorganized how people found food and meaning.

Seen in this wider frame, the murals at Vichama and Peñico do more than mourn a local drought, they quietly map a regional system adapting to global change.

Their characters show that survival meant keeping trade routes open, honoring fertility, and acknowledging the costs of imbalance between people and their environment.

Lessons from Caral’s walls

Caral’s experience does not offer an easy answer for modern climate change, but it points to choices that helped an early society handle shrinking rivers.

They spread risk across many communities, protected water, and relied on varied food sources.

Archaeologists note that ancient builders placed towns on high terraces, cared for riverbank forests, and built canals to stretch limited water. Those approaches still matter today, even with advanced tools and technology.

Researchers say the murals were created to ensure people would remember how severe the drought had been and what caused it.

They also explain that the final image, showing a toad struck by lightning, was meant to signal the long-awaited return of water and the hope of renewal.

The study is published in Nature.

Photograph: Caral Archaeological Zone.

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