The Washington PostDemocracy Dies in Darkness

Fossil study challenges assumptions about the ‘Great Dying’

Xiaokang Liu, left, Yi Wang and Luyi Miao look for fossil samples in the Guizhou province of China in 2018. (Xu Dai)
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About 250 million years ago, a catastrophic mass extinction event ravaged almost all life on Earth. Known as the Permian-Triassic extinction event, it’s still the planet’s most severe known mass extinction.

Long-standing scientific theory says the event, also called the Great Dying, was an evolutionary setback for Earth’s oceans. Only simple organisms remained, and it took between 5 million and 10 million years for more complex beings to slowly emerge.

But new research is challenging that long-held theory with fossil evidence of complex organisms and a diverse ocean ecosystem only about 1 million years after the extinction event.

Published in the journal Science, the study focuses on a large set of fossils from the Early Triassic epoch discovered near Guiyang in what is now South China. An international team of researchers date the fossils to about 1 million years after the Permian-Triassic extinction.

The fossil assemblage includes a dizzying array of life forms that would have swum in oceans once thought inhospitable to most life because of high surface temperatures, ocean acidity and periods of oxygen depletion.

“The fossils of the Guizhou region reveal an ocean ecosystem with diverse species making up a complex food chain that includes plant life, boney fish, ray-finned fish, crabs, lobsters, shrimp and [mollusks],” Morgann Perrot, who co-wrote the study as a postdoctoral researcher at McGill University, said in a news release.

The researchers found evidence of animals at all levels of the food chain and write that even though they did not find fossilized algae, they infer that it was part of the ocean’s food system.

How did previous scientists miss this kind of evidence of ocean life so soon after the extinction event? Perhaps they weren’t looking in the right place. Citing biases in terms of which fossils were preserved through the millennia and where researchers looked for such evidence, the researchers imply it’s time to lay the theory of a slow ocean recovery to rest.