The Great Dying: When Earth’s biodiversity nearly reached a dead end

Space · Published 26 October 2026 Swipe more like this →

In short: Imagine an ocean so oxygen-poor that modern fish would perish instantly, inhabited only by microbes and sluggish, blind organisms. This was the world 543 million years ago. It took an evolutionary storm to spark complexity, only for life to face its most catastrophic collapse nearly 250 million years later.

Before the Cambrian Explosion, Earth's oceans were a tranquil but alien landscape. During the Ediacaran period, roughly 543 million years ago, life was simple and lacked predators. Organisms moved slowly over microbial carpets because there was no evolutionary pressure to develop defenses or speed. This changed rapidly within a few million years as the Cambrian period ushered in an 'evolutionary storm,' introducing highly diversified organisms with advanced anatomical features. Life during this time was almost exclusively marine and consisted primarily of algae and single-celled bacteria. These early multicellular organisms were limited in variety compared to what followed. The seafloor was covered by a sticky microbial carpet that served as the primary food source.

This era of rapid diversification eventually gave way to the Paleozoic Era, characterized by constant revolutions and catastrophic extinctions. The most severe of these was the Permian-Triassic extinction, popularly known as 'the Great Dying.' Occurring approximately 250 million years ago, this event was so devastating that no class of life was spared. Approximately 90% of oceanic organisms and 70% of terrestrial types perished, almost terminating existence across our world. This period is considered one of the most chaotic stretches in history due to its constant biological revolutions. It represents the first era of our current eon. The event was so profound it left a clear pattern in the fossil record where life suddenly vanishes.

While the Cretaceous-Tertiary extinction (65 million years ago) is more famous for ending the dinosaurs, the Great Dying was significantly worse in scale. Scientists are still investigating the 'fingerprints' of this catastrophe, which may have been caused by severe volcanism, a nearby supernova, the formation of a super-continent, or a massive asteroid impact—or a lethal combination of all four. Researchers are currently searching for clues hidden within tiny capsules of cosmic gas to solve this mystery. They look for evidence buried under massive layers of earth that have remained hidden for eons. The investigation seeks to determine which specific environmental changes triggered the collapse.

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