New Evidence Is Challenging What We Know About the Deadliest Mass Extinction in History

Illustration for article titled New Evidence Is Challenging What We Know About the Deadliest Mass Extinction in History

The extinction at the end of the Permian period 252 million years ago was one of the darkest chapters in the history of life. Up to 96% of all marine species and 70% of terrestrial life forms vanished in a geologic blink.


But was the Great Dying really as sudden and devastating as its name would suggest? On land, perhaps not. In fact, new evidence is causing geologists to question whether a terrestrial mass extinction occurred at all.

At the Geological Society of America meeting this week, a team of scientists presented the results of a new dating analysis on the rock layers surrounding Dicynodon, a relative of early mammals whose death is held as key evidence for the terrestrial mass extinction at the end of the Permian. Surprisingly, their results show that Dicynodon vanished more than a million years before the onset of the Permian extinction in the marine record. What’s more, fossils of other plant and animal species, previously thought to have vanished along with Dicynodon, were found in younger rock layers.

The findings not only question the idea of a sudden die off—for some, they raise doubts that a land-based mass extinction really took place.

Other geologists are taking the findings with a grain of salt. As paleobiologist Jennifer Botha-Brink told Science News, while the new Dicynodon extinction dates do challenge our understanding of the end Permian, they don’t necessarily invalidate a mass terrestrial extinction. “People forget that biology is messy,” she said. “You can never draw a line of when the extinction was. It’s an interval; it’s a changeover.”

The Great Dying has always been a sticky, controversial subject among geologists. Theories on what exactly doomed the planet range from overactive microbes to massive volcanic outpourings and abrupt climate change. Now, some are questioning the very idea that the extinction was global. If one thing’s certain, it’s that we’ve got a long way to go before the case is closed on this fascinating chapter in Earth’s history.

[Read the full scientific paper at Geology h/t Science News]

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The main thing that happened in the Gastaldo et al. paper is that they argue that the Karoo Basin rocks that have been interpreted as being the age of the Permian-Triassic boundary are actually a few (hundred thousands of) years older. They’re fully Permian, rather than being partially Permian and partially Triassic. That would mean that the Karoo Basin can’t be used to actually answer questions on what happened, on land, during the Permo-Triassic mass extinction.

It’s like... if forensic investigators had been saying, from the best evidence available, that a crime scene was part of a murder spree, and then a new piece of evidence came in showing that the crime scene happened days before the spree.

This doesn’t mean that the Permo-Triassic mass extinction did not happen. This doesn’t mean that the Permo-Triassic mass extinction did not affect terrestrial life. It just means (if it’s correct) that the Karoo Basin is not the place to study the Permo-Triassic mass extinction.