20 Historical Events That Almost Killed EVERYONE

20 Historical Events That Almost Killed EVERYONE Q8P7Y2

Welcome to WatchMojo, and today we’re looking at the moments when humanity came dangerously close to going extinct.

Chernobyl (1986)

If it wasn’t for the quick thinking and incredible heroism of the response team, who knows what could have happened with Chernobyl? In the early morning of April 26, 1986, a reactor at the Chernobyl Nuclear Power Plant exploded and sent fatal amounts of radiation hurling into the atmosphere. The USSR and Eastern Europe were hit by dangerous radioactive fallout, and the immediate surrounding area became uninhabitable. Nearby cities were completely evacuated, and a massive effort involving over half a million people and the equivalent of $68 billion worth of clean-up was immediately launched. The reactor is currently enclosed within the Chernobyl New Safe Confinement, and cleaning efforts continue to this day. This was the workplace accident to end all workplace accidents.

The Large Hadron Supercollider (2010)

In 2010, the world’s most powerful particle accelerator - Large Hadron Collider - was ramping up to full power after its initial startup. Built to smash particles together at near light speed, it promised groundbreaking discoveries about the nature of the universe. Not everyone was excited. Some scientists and critics warned of terrifying possibilities: microscopic black holes, strange matter, even a vacuum decay event that could theoretically unravel reality itself. Lawsuits were filed, and headlines spread. Then, in March 2010, the first high-energy collisions began. In the end, nothing catastrophic happened, and particle physics took a major leap forward. But for a moment, humanity seriously debated whether flipping that switch might be the last decision it ever made.

Third Cholera Pandemic (1846–60)

In the mid-19th century, a deadly wave of disease swept across the globe. The Third Cholera Pandemic began in India before spreading through Asia, Europe, and North America. Cities were hit fast and hard, with little understanding of how the disease spread. At the time, many still believed in “bad air” rather than contaminated water. That misunderstanding made the outbreak far more dangerous, killing millions. Then came a breakthrough. In London, physician John Snow traced a major outbreak to a single contaminated water pump on Broad Street. Removing its handle helped stop the spread, marking one of the first victories of modern epidemiology. Without that shift in understanding, cholera - and diseases like it - could have continued spreading unchecked.

The Plague of Justinian (541–49)

In the 6th century, a silent killer swept through the ancient world. The Plague of Justinian spread across the Byzantine Empire and beyond, striking cities with terrifying speed. At its peak, it is believed to have killed thousands per day in Constantinople alone. Likely arriving through trade routes from Egypt, it spread rapidly across Europe, North Africa, and the Mediterranean. Entire communities were wiped out. Some estimates suggest the pandemic may have killed up to half the population where it appeared. The empire began to buckle under the weight of it. Trade collapsed, armies weakened, and Emperor Justinian’s ambitions to restore the Roman Empire faltered. No one understood what was happening. Without knowledge of bacteria or transmission, people were defenseless.

Holocene Extinction Event

This one isn’t some dark event in humanity's past: it’s happening right now, even as you watch this video. The Holocene extinction refers to the rapid loss of species driven largely by human activity. Deforestation, overhunting, pollution, and climate change are decimating Earth’s biodiversity. Scientists estimate extinction rates today are tens to hundreds of times higher than natural background levels. At first glance, that might not sound like an “end of the world” scenario. But ecosystems are interconnected. Remove enough species, and the systems that support life - food chains, pollination, clean water - begin to break down. In some regions, those cracks are already visible. If it continues unchecked, it has the potential to destabilize the very systems human life depends on.

Late Bronze Age Collapse (~1200 B.C.E.)

Around 1200 B.C.E., the ancient world just... unraveled. Within the span of a few short decades, major civilizations across the Mediterranean and Near East began to collapse. The Late Bronze Age collapse saw the fall of the Mycenaeans, the Hittite Empire, and the weakening of Egypt. Cities burned. Trade routes vanished. Entire regions were plunged into chaos. No single cause explains it. Instead, it appears to have been a perfect storm: climate change, drought, famine, internal rebellion, and invasions by displaced warriors. Many achievements of the ancient age vanished into prehistory, setting back human progress. Writing disappeared in some regions. Populations declined. It would take centuries for parts of the world to recover.

Bonilla Comet (1883)

In 1883, an astronomer in Mexico saw something impossible. José Bonilla reported hundreds of dark objects crossing the face of the Sun over the course of two days. At the time, no one could explain what he had witnessed. More than a century later, scientists revisited Bonilla's photographs and came to a chilling conclusion: Bonilla may have been observing fragments of a comet passing shockingly close to Earth. They may have come within a few hundred to a few thousand kilometers. If true, the objects may have been tens to hundreds of meters across. Had even a fraction of those fragments entered Earth’s atmosphere, the results could have been catastrophic. A direct impact - or multiple impacts - might have caused regional or even global devastation.

Younger Dryas (~12,800 B.C.E.)

Around 12,800 years ago, the Earth suddenly plunged back into near-glacial conditions. The Younger Dryas saw temperatures drop dramatically across the Northern Hemisphere in what should have been a steady warming period after the last Ice Age. In a matter of decades, ecosystems shifted, and megafauna populations declined. Early human societies were forced to adapt or move. The cause remains debated. One leading theory points to a massive influx of freshwater into the North Atlantic, disrupting ocean circulation. Another, more controversial idea suggests a comet impact may have triggered the event. Either way, the result was the same: the sudden climate shock put both ecosystems and early human populations under intense pressure.

GMO Soil Bacteria (1994)

In the 1990s, scientists engineered a strain of Raoultella planticola designed to turn crop waste into ethanol. It sounded like a miracle of science and a brand new source of fuel. But early lab tests raised a disturbing possibility: the modified bacteria also produced alcohol at levels that appeared to inhibit plant growth in treated soil. Some researchers, including Elaine Ingham, warned that releasing it prematurely could devastate crops. In worst-case scenarios, it could potentially spread through soil systems in unpredictable ways. Those claims were later criticized as overstated, based on limited lab conditions. The organism was never deployed commercially. Even so, the episode revealed how a single miscalculation in genetic engineering could ripple outward - to potentially devastating effect.

The Tunguska Event (1908)

At dawn on June 30, 1908, something tore through the skies over Siberia. Then the world exploded. A massive airburst flattened over 800 square miles of forest, snapping an estimated 80 million trees like matchsticks. Witnesses described a blinding fireball, a shockwave that knocked people off their feet, and heat intense enough to scorch the ground. The blast has been estimated at up to 50 megatons - hundreds of times more powerful than Hiroshima. Luckily, it happened in one of the most remote places on Earth. If that same object detonated over a major city, the death toll would have been staggering. A slightly larger object - or a different angle of entry - could have triggered far wider atmospheric effects. If it fell hours later, it would have annihilated St. Petersburg.

The Great Genetic Bottleneck (~800,000-900,000 Years Ago)

Nearly a million years ago, humanity almost disappeared before it even really had a chance to get going. Genetic evidence suggests that early human ancestors went through a severe population bottleneck, with numbers dropping to as few as roughly 1,000 breeding individuals. That doesn’t mean just 1,000 people total, but it is a shockingly small population. That low population level lasted for a staggering 100,000 years. For one hundred millennia, generation after generation of our ancestors lived on the razor's edge of extinction. The exact cause remains unknown. Scientists point to climate shifts, environmental stress, or a combination of factors. Whatever the cause, modern humans likely descend from this tiny, fragile population.

Kola Superdeep Borehole (1970-95)

In the 1970s, Soviet scientists embarked on a straightforward mission: to drill as deep into the Earth as possible. The Kola Superdeep Borehole, a 7.6-mile-deep chasm, remains the deepest artificial point on Earth. The experiments conducted there told us a great deal about both life on earth and the planet's makeup. But what if they’d gone deeper? Experts of the time worried about drilling into the Earth's mantle. Could such an experiment have triggered volcanic activity or seismic shifts? Luckily, the mantle remains unbreached. The project stalled in 1995 due to both skyrocketing temperatures and costs. Let’s just hope it wasn’t also a case of humanity dodging a geological bullet.

Nuclear War Games (1979)

In 1979, a training tape meant to simulate a Soviet nuclear attack was accidentally fed into NORAD's live warning system. The resultant scare nearly led to nuclear Armageddon. Alarms blared as screens lit up with what appeared to be an incoming missile barrage. Military commanders scrambled to respond, alerting nuclear forces and bringing the world to the brink of catastrophe. Thankfully, cool heads noted that nothing was coming up on radar or seismic sensors. Fortunately, the error was caught before any retaliation orders were issued. Still, the incident exposed just how close humanity could come to accidental annihilation thanks to human error. It was a stark reminder that in the nuclear age, even a single man's accident could have deadly consequences.

Eruption of Mount Thera (~1600 B.C.E.)

Volcanoes have shaped civilizations thanks to the fertile soils left in their fiery wake. But their destructive power also holds civilization-ending potential. Krakatoa’s 1883 eruption unleashed energy equivalent to 200 megatons of TNT, devastating Java and Sumatra. In 1815, Tambora’s eruption brought “the year without a summer. ” Ash in the atmosphere sent global temperatures plunging, sparking worldwide famines. But Mount Thera, which erupted around 1600 BCE, takes center stage in volcanic history. Its eruption obliterated much of the Minoan civilization, the real-life inspiration for Atlantis. The shock of the explosion sent tsunamis cascading through the Mediterranean Sea, devastating many early human settlements. Had the aftereffects been more widespread, humanity might have been set back centuries - or worse.

“The Carrington Event” (1859)

In 1859, the sun unleashed a geomagnetic storm so powerful it electrified telegraph lines, sparked fires, and created auroras visible near the equator. Known as the Carrington Event, it was a cosmic warning shot to the future of electronic-age humanity. At the time, the world ran on steam, coal, and oil. Electricity was both rare and simple, with the effects of the solar storm localized and minimal. Today, our interconnected digital infrastructure is far more vulnerable. A modern equivalent could fry satellites, disable power grids, and plunge modern society into utter chaos. Estimates suggest such an event would cost trillions in damage. It would take a modern society years to recover from a repeat of the Carrington Event.

Cuban Missile Crisis (1962)

The Cuban Missile Crisis brought humanity to the very brink of nuclear annihilation. As the United States discovered Soviet missile installations in Cuba, tensions escalated into a 13-day standoff. Behind the scenes, military leaders on both sides advocated for war. U.S. generals proposed an invasion of Cuba. Soviet commanders in Cuba were authorized to launch tactical nuclear strikes if attacked. President John F. Kennedy and Soviet Premier Nikita Khrushchev ultimately chose diplomacy over devastation. They negotiated a secret deal that removed missiles from both Cuba and, eventually, Turkey. The crisis was a stark reminder of how human decision-making narrowly averted catastrophe. Had cooler heads not prevailed, civilization as we know it could have ended in nuclear fire.

The Chicxulub Impact (66,000,000 B.C.E.)

Near misses with asteroids remind us how precarious life on Earth can be. In 1989, the asteroid 4581 Asclepius skimmed past our planet at a cosmic hair’s breadth. Now imagine an asteroid not missing - like the Chicxulub impact. A space rock the size of Mount Everest slammed into what is now Mexico’s Yucatán Peninsula more than 66 million years ago. The collision released a level of energy that is difficult to comprehend. Firestorms and acid rain ensued. The impact also triggered a “nuclear winter” that blocked sunlight. This instant ice age collapsed most ecosystems, wiping out 75% of life on Earth, including most dinosaurs. A similar impact in the future would almost certainly deliver equally deadly results.

Spanish Flu (1918-20)

In an increasingly globalized world, pandemics reveal the vulnerable underbelly of human civilization. COVID-19 paralyzed the planet, killing millions and exposing the fragility of our interconnected systems. But even this pales in comparison to the Spanish flu of 1918. Emerging in the shadow of World War I, the influenza virus infected one-third of the global population. The death toll of the Spanish Flu was estimated by many as 50 million people. This far eclipsed the death toll of the war itself. With no antibiotics to treat secondary infections and limited medical knowledge, it spread with terrifying speed. It devastated urban centers and remote villages alike. Infrastructure crumbled, economies stalled, and communities were pushed to the brink. A deadlier communicable virus could ostensibly destroy humanity outright.

Ice Age (194,000 -135,000 BCE) & The Toba Supervolcano (70,000 B.C.E.)

During the devastating glacial periods, humanity teetered on the brink of extinction. As ice sheets expanded across vast swaths of the planet, the climate grew colder and drier. In this era before agriculture, food sources were decimated. Early humans were left with a choice: migrate or perish. Many did both. Through the millennia and centuries, Homo sapiens struggled to survive. The eruption of Toba the supervolcano further affected global temperatures around 70,000 years ago. Genetic evidence suggests that Homo sapiens dwindled to as few as 1,000 individuals. The "population bottleneck" was so severe it could have ended our species entirely. Survival demanded ingenuity, as small bands clung to life near Africa’s coasts, relying on marine resources for sustenance.

The Black Plague (1346-1353)

The Black Plague was one of the deadliest diseases in human history, killing an estimated 50 million people worldwide. It destroyed nearly 1/2 of Europe's population alone. The disease tore through towns and cities with terrifying speed. It spread along trade routes, leaving devastation in its wake. Societies crumbled as fear and superstition gripped survivors. Labor shortages reshaped both the economy and social hierarchies. But the plague wasn’t just a natural disaster; it was also an early example of biological warfare. In 1347, Mongols besieging the city of Caffa allegedly launched plague-ridden corpses over the walls, likely accelerating its spread into Europe. This dark precedent highlights the risks of weaponized diseases today, as advancements in biotechnology make pathogens like plague or smallpox potential weapons.

Trinity Test (1945)

The Trinity Test marked the birth of the nuclear age. It was an age born in fire with the potential to end just as quickly. As the first-ever detonation of a nuclear device, it was an experiment shrouded in uncertainty. Some Trinity scientists even feared that the explosion would ignite the Earth’s atmosphere. Such a chain reaction could consume the planet in fire. While those fears proved unfounded, the test confirmed humanity’s ability to unleash catastrophic destruction. Since then, nuclear weapons have brought us perilously close to annihilation. Near-misses, from misinterpreted radar signals to mistaken drills, remind us how easily things could spiral out of control. The haunting specter of the Trinity Test’s hypothetical conflagration mirrors the real, ongoing threat of nuclear war.

Which of these near-extinction events do you think came closest to ending humanity? Did we miss a moment where humanity almost didn’t make it? Let us know in the comments!