Science writer Andrew Lawler probes new ideas about how El Niño transformed ancient human societies—and what this means for our future.
As a child, I peered through a second-story window at an eerie orange dusk that had fallen in Norfolk, Virginia, where I grew up. A tropical storm was roaring into the town’s harbor, and I stood transfixed as a single wave suddenly rose up, sweeping toward our neighbor’s five-meter motorboat tied to a dock. Snapping the line, the foaming mountain of water catapulted the craft into the air and smashed it against the rocks on shore. It was my first experience of nature’s violence and power.
Throughout history, extreme weather has been the enemy of our species. Floods, storms, droughts, and prolonged cold spells are a constant backdrop to human history. The famous kamikaze, or divine wind, wrecked the fleet of Kublai Khan in 1281 and destroyed Mongol dreams of conquering Japan, while a drying climate uprooted indigenous groups from large parts of the American Southwest centuries before the arrival of Europeans.
But extreme weather may bring more than wrack and ruin to human societies. New archaeological research suggests that abrupt climate shifts and severe weather events can also create novel opportunities for radical change. Indeed, the earliest civilization in the Americas may owe its beginnings in part to such natural calamities.
“You don’t get through climatic or environmental change without changing your culture,” says University of Maine archaeologist Dan Sandweiss. In his studies of ancient societies along the Peruvian coast, Sandweiss has found evidence that one of the world’s most notorious weather patterns—El Niño—may have helped to spur the rise of the New World’s earliest cities, and may also have triggered their fall.
Sandweiss’s research certainly bears thinking about today, as a new El Niño gathers force in the central and eastern Pacific Ocean. In August, the US National Oceanic and Atmospheric Administration warned that this year’s El Niño could be more devastating than any since 1950, when comprehensive record keeping on the pattern began. And this forecast has prompted widespread warnings about surging coastal storms and disastrous mudslides in regions such as southern California.
El Niño, a Spanish phrase meaning “Christ child,” acquired its deceivingly mild moniker in the 19th century, when sailors noticed that the generally cold waters off the coast of Peru and Ecuador turned warm some years around Christmas time. Scientists began to study the phenomenon in earnest starting in the 1920s, and their research now shows that El Niño recurs once or twice every decade with varying intensity. During the winter of 1997 and 1998, for example, weather associated with El Niño took an estimated 24,000 lives and cost more than US $34-billion in damage around the world.
But all classic El Niños are born from the same conditions. A band of warm water forms in the central Pacific, while a high-pressure system develops to the west and a corresponding low settles along the eastern edge of the ocean.
In severe years, these changes in the sea and sky set in motion complex interactions with dramatic repercussions around the globe. Grasslands in southeast Australia tend to dry up and catch fire, and packs of Category 3, 4, and 5 typhoons rove the eastern Pacific, threatening Guam and Japan. Already this year, a record-breaking 22 major cyclones have spun across the northern half of the Pacific Ocean. When Hurricane Patricia struck Mexico’s coast on October 23, it was the most powerful storm in terms of barometric pressure recorded in the Western Hemisphere.
But northern Peru tends to be one of the hardest hit places. The waters off its Pacific coast are home to one of the planet’s most productive fisheries. During an El Niño year, however, the warming waters kill mollusks, seabirds, and sea lions, and force the migration—or interfere with the reproduction—of vast numbers of fish. In a country that relies on its anchovy catch to make fish meal and is the world’s top producer of this commodity, there are fears of serious repercussions.
A strong El Niño also brings heavy downpours that inundate northern Peru’s coastal deserts and the parched hills that huddle near the foot of the Andes there. This rainfall in turn triggers heavy floods that send debris down the steep stream beds, destroying fields and irrigation works and sweeping away homes and bridges all the way to the ocean’s edge.
The repercussions don’t end with the cessation of rain. In the aftermath of an El Niño in 1578, a Spanish priest watched in horror as remaining crops were “eaten by crickets and locusts and some green worms and yellow ones and other black ones that were bred from the putrefaction of the earth.” Then came mice “the size of medium rabbits” that gobbled up any scrap of surviving food. And often, along with the threat of famine and swarms of insects, come deadly tropical diseases that attack already weakened human populations.
Records of El Niños before the arrival of the Spanish in the 16th century are scarce. Peru’s ancient indigenous cultures did not leave any written records that researchers can understand today. And the lake bottoms, trees, and glaciers that typically provide scientists with data on ancient local climates are either in short supply on this stark coast or are difficult to analyze.
But Sandweiss found a clue to Peru’s ancient climate in 1980 when he took a walk among piles of shells discarded 6,500 years ago near the fishing port of Chimbote. The young archaeologist picked up a few shells that he could not identify and took them to an expert in Lima. She said that they must have come from the warmer Ecuadorian coast 640 kilometers to the north. When he told her their origin, she replied, “Impossible.” The shellfish, she added, couldn’t survive in cold Peruvian waters.
Sandweiss had stumbled on some of the first physical evidence for a climate regime that predated periodic El Niños. During that earlier regime, waters off the northern coast of Peru were generally warm all year round, and small populations of human hunters and gatherers roamed along the coast. But things began to change some 5,800 years ago. For reasons that remain unclear, Peru’s northern waters became predominantly cold, with aperiodic warming of the seas in winter—the familiar El Niño pattern.
In the centuries that followed this shift, indigenous people began to build the earliest known monumental structures in South America. One such structure, a mound called Los Morteros, located on the north coast, rose 15 meters in the air, and sprawled over an area the size of three soccer fields. And by 2600 BCE, what is arguably the first city in the Americas took shape at Caral in the nearby Supe Valley. Urban centers soon sprang up across the valley. “The whole area goes boom,” says Sandweiss.
Sandweiss now thinks the sudden penchant for urban living in Peru was closely connected to the rise of recurrent El Niños. The extreme weather seems to have happened only once in a lifetime or less during this era, but the resulting floods posed a new threat to coastal dwellers, a threat that became embedded in their collective memories. Dealing with these natural catastrophes required a different sort of society. “This was an opportunity for political entrepreneurs who could say, ‘Hey, I can solve the problem!’”Sandweiss suggests.
Cause and effect in human history is difficult to prove. But the emergence of El Niño appears to have spurred at least in part the dramatic transformation of Peruvian coastal life. Temples and irrigation works multiplied in size and scope, concrete signs that people were developing new belief systems to deal with the crises and new forms of infrastructure to prevent, minimize, and repair destruction caused by El Niño. And these changes seem to have given rise to a society capable of coping with the weather challenge.
About 850 BCE, however, for reasons that remain obscure, El Niño began to take place on a more frequent and intense basis—about once or twice a decade. And suddenly, construction of the big temples ceased. “There is no sign of a demographic collapse,” Sandweiss says. Instead, the sudden increase in natural disasters may have undermined support for established beliefs and the prevailing political system.
Centuries passed before large temples again appeared: this time they were bigger than before and they rose from the middle of elite urban enclaves. Clearly a different culture had emerged as the drumbeat of disaster increased in tempo.
Did El Niño help spur and then reshape the New World’s first civilization? Sandweiss is quick to acknowledge that further research is needed to pin down the timing of both climate shifts and human activities.
But what’s compelling about Sandweiss’s theory is the underlying idea that humans are not passive victims of nature’s ravages. In this scenario, the challenges thrown at us by the vagaries of weather shake us up in ways that can be as creative as destructive. We don’t just suffer through natural disasters; these events transform us. They are part of who we are.
Today, humans are altering our planet’s weather through our own actions. And in this era of global warming, the question facing our species is whether we will rise to the occasion, as ancient Peruvians did almost six millennia ago, when they collaborated to build a new faith and political organization to confront a daunting climate challenge in a creative fashion. “There may well be lessons here for the modern world and our future,” concludes Sandweiss.
The world leaders who are currently in Paris for the United Nations Climate Change Conference hope to hash out a legally binding agreement on climate to reduce carbon emissions. Whatever the outcome, our species will need to consider other ways to limit and counter climate change and devise ways to protect the vulnerable populations who live along the islands and coasts of the Arctic, Pacific, and Indian oceans, and who stand to suffer the most from more intense storms and rising sea levels.
This can be done. Before Hurricane Patricia crashed ashore, Mexican authorities did a remarkable job preparing for a disaster. Television, radio, and social media sites warned those likely to be affected, while public officials with bullhorns shouted warnings in the streets of cities and towns in the storm’s projected path. Only six deaths in Central America were officially linked to the storm. Some of that was luck—Patricia did not make landfall in a major population center and quickly lost strength over the coastal mountains. But successful prevention measures can be expanded to other places, while we work on long-term plans to ensure the safety of the billion-plus people who live in low-lying coastal areas.
Retooling our civilization to ensure our survival will not be simple, cheap, or smooth. There is no guarantee of success. But the urgent threat of climate change and more extreme weather events could prompt us to rethink our values, create new organizations, and fix what no longer works. It’s a call for reinvention.
What I remember most about the tropical storm that battered my home long ago is not the screaming wind and pounding surf. What sticks in my mind is the next morning, when the Sun appeared and the clouds blew out to sea.
Neighbors spontaneously formed teams to clear wreckage from yards and haul damaged boats to high ground. Those who had generators prepared hot food and coffee and set up card tables on the sidewalks to hand out this fare. For a few crucial hours, our community rose to the occasion, and we were, despite the trauma of the long night, the better for it.
