Was Every Mass Extinction Caused by an Asteroid?
Was Every Mass Extinction Caused by an Asteroid?
My father taught school in a village so small that a trip to an actual movie theater was something you could brag about for a week. The outing he remembered best was the one we took alone together, just the two of us, to see One Million Years B.C. It was a film that had already been out for years by the time we finally caught it, but one he had always wanted to see.
I did not make it far. The dinosaurs on screen were too much for me, and I begged to leave. My father handed me some money for the diner next door, told me to eat and wait, and went back inside to finish the movie alone.
It is a funny memory now. Years later, I learned two things in school that quietly undid it: non-avian dinosaurs and humans never shared the planet, and Earth has lived through this kind of ending five times before.
A father and son walking toward a small rural movie theater to watch One Million Years B.C., a nostalgic childhood memory before learning about Earth's mass extinctions.
The Big Five Don't All Fit the Asteroid Story
Five mass extinctions sounds like five versions of the same disaster: something enormous falls from the sky, and the world resets. Only one of them actually fits that picture.
Earth's "Big Five" mass extinctions are the end-Ordovician, end-Devonian, end-Permian, end-Triassic, and end-Cretaceous events, according to the National Park Service. Each wiped out a large share of life, then handed the empty niches to whatever survived. Only the end-Cretaceous event, which also ended the non-avian dinosaurs, is tied to a confirmed asteroid strike.
That distinction has a name in the research literature. A 2023 classification framework in National Science Review sorts the Big Five by what set each one off: the end-Permian and end-Triassic as volcanically triggered, the end-Ordovician and end-Devonian as driven by the biosphere itself reshaping the planet's carbon cycle, and the end-Cretaceous alone as bolide-triggered. I'd always filed all five under the same asteroid-shaped assumption, so seeing them split apart like that was the first surprise in putting this piece together.
This framework matters, because the same paper places modern, human-caused carbon release in the biosphere-triggered category, not the volcanic one. The thing that reshaped the carbon cycle those first two times was life itself, evolving. This time, the paper suggests, it's us.
The one everyone already knows, the asteroid strike that ended the dinosaurs, turns out to be the outlier in that scheme, not the template.
Scientific illustration of Earth's Big Five mass extinctions showing five catastrophic events that reshaped life and biodiversity across deep geological time.
What Killed the Other Four Wasn't a Rock From Space
Four of the five didn't need anything to fall from orbit. The planet did this to itself, more than once, using nothing but its own oceans, ice, and volcanoes.
The end-Ordovician extinction, about 444 million years ago, arrived through glaciation. A rapid ice age over the ancient supercontinent Gondwana pulled sea levels down and drained the shallow shelves where much marine life lived.
Then the ice melted just as fast, flooding everything again. The National Park Service describes the damage landing in two short, brutal pulses rather than one long decline. That same 2023 classification paper goes further, suggesting the glaciation itself may have been triggered from within: early life reshaping the ocean's carbon chemistry, then absorbing the consequences.
The end-Devonian extinction, roughly 372 million years ago, is messier still. The Park Service lists global cooling, volcanic activity, a possible comet or extraterrestrial impact, and a bloom-and-suffocate cycle (nutrient runoff feeding algae blooms that stripped oxygen from the water) as competing explanations, without settling on one.
That refusal to settle is the point. The usual mental image of a mass extinction is a single dramatic scene; the Devonian looks more like a slow, multi-front siege that lasted long enough to collect several plausible culprits.
Then came the end-Permian, 251.9 million years ago, and the numbers stop being comparable to anything else on this list. The National Park Service estimates that about 96 percent of species were lost.
The number, like most of what we know about the Big Five, is built mainly from the marine invertebrate fossil record, the group with the best preservation through deep time. The likely driver was the Siberian Traps, a colossal volcanic eruption whose carbon dioxide and sulfur dioxide output appears to have driven both climate change and ocean acidification.
The end-Triassic followed a similar script about 200 million years ago: roughly 80 percent of species gone, tied again to volcanism, this time linked to the Atlantic Ocean prying the supercontinent Pangaea apart. What emerged afterward was ecological room, space that dinosaurs, until then a minor group, spent the next 135 million years filling.
Four extinctions, one recurring engine: not a strike from outside, but the planet's own chemistry running out of slack. None of the four have the drama of a fireball, which is probably why I'd never really registered any of them until I sat down to write this. It's hard not to read the pattern as a warning about what "catastrophe" actually tends to look like, not a single blow, but a slow tightening most of the victims never saw coming.
The End-Permian mass extinction with massive Siberian Trap volcanic eruptions, collapsing ecosystems, and the largest biodiversity loss in Earth's history.
Was the Cretaceous Extinction Really That Fast?
Then there is the extinction everyone already knows, and it earns its fame honestly, though not quite the way people picture it. The impact itself was over in an instant. What it triggered was not. That gap is the part I keep turning over: a few seconds against years of consequence.
The end-Cretaceous extinction, 66 million years ago, began with the Chicxulub impact. The asteroid strike triggered abrupt climate disruption and plunged Earth into darkness, killing off the non-avian dinosaurs along with much of marine life, according to the National Park Service.
The familiar shorthand is "an asteroid killed the dinosaurs." The more precise version is that the impact disrupted photosynthesis and collapsed food webs, with effects that reached far beyond the initial blast.
The Park Service adds one detail worth sitting with: the ecological space the dinosaurs left behind is what let mammals, who had spent the whole Cretaceous living in the shadow of a world dinosaurs already ran, finally expand into daylight. Ours is one of the lineages that walked through that door.
Maybe that is the uncomfortable footnote to the most famous extinction of all. The room we are standing in was cleared out by a catastrophe, not offered to us on purpose.
The Chicxulub asteroid impact that triggered the end-Cretaceous mass extinction, causing global darkness and killing off the non-avian dinosaurs.
Is a Sixth Mass Extinction Already Underway
Every extinction on this list eventually got a name once researchers worked out what caused it. The one possibly happening right now does not have that luxury, because it is still going.
A 2015 analysis by Gerardo Ceballos and colleagues found current extinction rates running far above the natural background rate, with human activity identified as the driver. The researchers described this as a sixth mass extinction already in motion.
Amphibians make the case concretely. Research on frogs and salamanders by David Wake and Vance Vredenburg found land-use change, climate shifts, and the rapid spread of disease working together, with more than a third of the world's amphibian species considered threatened as a result.
Not every region is losing species at the same pace, and the label itself is contested. A 2025 review in Trends in Ecology and Evolution argues that documented losses to date fall far short of the roughly 75 percent threshold that defined the Big Five, making the comparison premature. Researchers who do accept the framing are careful to call it a process still underway, rather than a finished, dated catastrophe like the other five.
That same 2023 classification is where this gets personal. The paper doesn't file today's carbon release next to the volcanoes of the Permian and Triassic.
It files it next to the Ordovician and the Devonian. Those are the two extinctions this article opened with, the ones caused by life itself reshaping the planet's chemistry. Of everything I ran into researching this, that's the line that actually stayed with me. One way to read this is the least comfortable version of the whole subject: for the first known time, the species doing the reshaping might also be the one that has to live through what comes next.
Life may be able to survive plenty of extremity, at least in theory. Saturn's moon Enceladus hides a sunless ocean beneath its icy shell, one that vents water vapor into space through cracks at its south pole.
Scientists consider it a potentially habitable environment, not confirmed to host life, but a place where the right ingredients exist. None of that would rescue what is happening to this one.
Modern environmental crisis showing climate change, biodiversity loss, deforestation, melting glaciers, and human-driven risks of a sixth mass extinction.
| Extinction Event | Approximate Date | Primary Driver |
|---|---|---|
| End-Ordovician | ~444 million years ago | Rapid glaciation and sea-level collapse |
| End-Devonian | ~372 million years ago | Disputed: cooling, volcanism, possible impact |
| End-Permian | ~251.9 million years ago | Siberian Traps volcanism |
| End-Triassic | ~200 million years ago | Pangaea rifting and volcanism |
| End-Cretaceous | ~66 million years ago | Chicxulub asteroid impact |
If there is one thing life keeps teaching, it is that nothing holds forever. What kind of ending are we actually heading toward? Does decline arrive all at once, or does it creep in the way the Ordovician ice did, one slow squeeze at a time?
I do not know that extinction is avoidable, for us any more than it was for anything else on that list. Standing in front of what the planet has already done four times over, that feels less like pessimism than arithmetic.
There is one more piece of this that has nothing to do with fossils. Years after that afternoon at the theater, I saw Raquel Welch again — the same actress from One Million Years B.C., pinned to the wall of Andy Dufresne's cell in The Shawshank Redemption. For a moment, without meaning to, I thought of my father, sitting alone in that dark theater, finishing a movie his son could not sit through.
An elderly man reflecting on childhood memories beneath a Raquel Welch poster while contemplating Earth's deep history, extinction, and humanity's impermanence.
Sources & References
National Park Service, "Mass Extinctions Through Geologic Time"
Algeo, T.J. & Shen, J., "Theory and Classification of Mass Extinction Causation," National Science Review, 11(1), nwad237, doi.org/10.1093/nsr/nwad237
Ceballos et al., "Accelerated Modern Human-Induced Species Losses: Entering the Sixth Mass Extinction", Stanford MAHB
Wake & Vredenburg, amphibian decline research, NCBI Bookshelf
Wiens, J.J. & Saban, K.E., "Questioning the Sixth Mass Extinction," Trends in Ecology & Evolution, 40(4), 375-384 (2025)
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