251 MILLION years ago, at the end of the Permian period, life on Earth was almost completely wiped out by an environmental catastrophe of a magnitude never seen before or since. All over the world complex ecosystems were destroyed. In the sea, coral reefs, fishes, shellfish, trilobites, plankton, and many other groups disappeared. On land, the sabre-toothed gorgonopsian reptiles and their rhinoceros-sized prey, the dinocephalians and pareiasaurs, were wiped out forever. Only 5 per cent of species survived the catastrophe, and for the next 500,000 years life itself teetered on the brink of oblivion. What terrible event could have wrought such havoc?
Two theories have been proposed – the impact of a huge meteorite or comet over 10 kilometres in diameter, or a massive and prolonged volcanic eruption. Up to now the evidence has been equivocal. But the data has been accumulating over the past 10 years, and the picture is now clear enough to say with some certainty what happened.
An impact might seem a tempting model. A massive catastrophe demands an extraordinary explanation – something unexpected, something from outer space. And we know that impacts can cause mass extinctions. It seems that the dinosaurs and many other groups of animals and plants were wiped out 65 million years ago by the impact of a huge meteorite in modern day Mexico. The crater has been found, there is good evidence for the shock wave, and for the fallout rocks and dust all round the world.
In February 2001, a team of scientists claimed they had found clear evidence that the mass extinction at the end of the Permian was also…
