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 per cent of all marine species and 70 per cent 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 raises doubts that 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 terrestrial mass extinction really took place.
But many geologists are taking the findings with a grain of salt. As palaeobiologist Jennifer Botha-Brink told Science News, while the new Dicynodon dates raise questions about our understanding of the end Permian, they don’t necessarily invalidate a 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 premise 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.