About 250 million years ago, pretty much everything died.

Only one in ten species of plant and animal survived the largest-known, most-catastrophic die-off of life on Earth, which is thought to have been the only mass extinction event to have significantly affected insects. Marine species were hit worst, with 96 percent dying. Sea scorpions, trilobites and certain types of starfish were permanently made extinct, and only two and three percent of snails and squid survived, respectively.

A review in Nature Geosciences from Zhong-Qiang Chen, of the China University of Geosciences in Wuhan, and Michael Benton of the University of Bristol, concludes that it took ten million years before the Earth was able to fully recover.


The disaster, known as the Permian-Triassic extinction event and referred to by Nasa as "The Great Dying", occurred when the Earth's continents were mashed-up into one landmass, known as Pangaea. It's thought to have been triggered by a combination of climate change, acid rain, ocean acidification and anoxia.

Chen and Benton examined analyses of rock sections found in China and across the world to try and get an idea of the timeline of extinction. They claim that after the initial cataclysm, grim conditions returned in bursts for five or six million years with repeated carbon and oxygen crises, global warming, and other nasty events.

Animals that did manage to recover reasonably quickly and rebuild their ecosystems were hit repeatedly, and as a result, permanent ecosystems took around five million years to re-establish. Benton said: "Life seemed to be getting back to normal when another crisis hit and set it back again. The carbon crises were repeated many times, and then finally conditions became normal again after five million years or so."

It was only after the environmental shocks eased that complex ecosystems were able to re-emerge. The species that emerged from the events formed the basis of modern-style ecosystems -- consisting in the sea of ancestral crabs, lobsters, and the first marine reptiles, and on the land of tetrapods which eventually became the dinosaurs.


Chen said: "It is hard to imagine how so much of life could have been killed, but there is no doubt from some of the fantastic rock sections in China and elsewhere round the world that this was the biggest crisis ever faced by life."

Benton added: "We often see mass extinctions as entirely negative but in this most devastating case, life did recover, after many millions of years, and new groups emerged. The event had re-set evolution. However, the causes of the killing -- global warming, acid rain, ocean acidification -- sound eerily familiar to us today. Perhaps we can learn something from these ancient events."

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