Mass extinction events
The Killing That Took Ten Million Years to Finish
The asteroid that ended the dinosaurs was almost merciful — the extinction event before it killed 96% of all life on Earth, and it did so slowly, in waves, over millions of years.
The Idea
When people think of mass extinctions, the picture is usually cinematic: a rock from space, a wall of fire, darkness, and silence. The Cretaceous-Paleogene extinction 66 million years ago fits that template reasonably well. But the deadliest extinction in Earth's history — the Permian-Triassic event, 252 million years ago — unfolded more like a slow catastrophe than a sudden blow, and that distinction changes everything about what we think extinction actually means. The Permian-Triassic boundary is sometimes called 'the Great Dying.' Nearly 96% of marine species and around 70% of terrestrial vertebrate species vanished. The trigger was volcanic — the Siberian Traps, one of the largest volcanic provinces ever to exist, erupted over roughly a million years, releasing enough carbon dioxide and sulfur dioxide to destabilise the climate, acidify the oceans, and deplete oxygen in the water column. What's striking is that the killing didn't happen in a single pulse. Geologists and palaeontologists now read the rock record as showing multiple extinction waves: initial shocks, partial recoveries, then further collapses. This matters because it reframes what 'extinction event' means. It isn't a switch being flipped — it's an ecosystem being worn down until its buffers are exhausted. Species that survived one wave found themselves in a world with fewer resources, fewer ecological partners, and less resilience to absorb the next shock. The Great Dying was, in a sense, a lesson in how systems fail.
In the World
In the Karoo Basin of South Africa, the rock layers tell the story with unusual clarity. Palaeontologist Michael Benton and his colleagues have spent years reading the Permian-Triassic boundary there through the fossils of a group called dicynodonts — sturdy, beaked herbivores that dominated Permian landscapes much as large mammals dominate ours today. Below the extinction horizon, dicynodont fossils are abundant and diverse. Above it, almost nothing. Then, briefly, a handful of species reappear — survivors clinging to a degraded world. What the Karoo record shows is not a single wipeout but a landscape being destabilised repeatedly. Benton's team found evidence of at least two distinct extinction pulses within the broader event, separated by a partial recovery — suggesting that ecosystems got close to stabilising, then were knocked back again by further volcanic emissions or cascading ecological collapse. Some researchers describe the aftermath as a 'dead zone' lasting up to ten million years, during which biodiversity was so suppressed that normal evolutionary diversification barely functioned. The Triassic that eventually emerged on the other side looked almost nothing like the Permian world before it. The slate had been wiped so thoroughly that entirely new body plans and ecological roles had room to evolve — eventually including the dinosaurs, who were themselves products of a world rebuilding from the most thorough destruction life has ever endured.
Why It Matters
There's a temptation to treat mass extinctions as dramatic but distant — geological footnotes that belong to deep time. But the mechanisms that drove the Great Dying are not exotic. Rapid carbon release, ocean acidification, warming, oxygen depletion, habitat collapse — these are processes with modern analogues, which is precisely why palaeontologists find themselves increasingly in conversation with climate scientists. More personally, the Great Dying offers a way of thinking about systemic fragility that goes beyond biology. The idea that a system can absorb shocks up to a point, partially recover, and then fail catastrophically under the next stress — not because that stress was uniquely severe, but because resilience had already been spent — applies far beyond geology. It describes how ecosystems, institutions, and perhaps even personal circumstances tend to break: not all at once, but in accumulated stages that only look inevitable in retrospect. Knowing that 96% of species were erased and life still found a way forward is, depending on your temperament, either deeply comforting or a useful corrective to any assumption that the particular forms of life we value are somehow guaranteed to persist.
A Question to Ponder
If extinction events don't happen all at once but in waves — with partial recoveries in between that create false hope — how would you know, from inside such a system, whether you were in a lull or a genuine recovery?
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