What really caused the largest mass extinction in Earths history?
The Permian-Triassic extinction, as it is called, is not the one that wiped out the dinosaurs. Nor does the cause appear to have been a meteorite strike, as in that famous event. The most likely explanation for the disappearance of up to 90 percent of species 250 million years ago, said David Bottjer, is that “the earth got sick.” Bottjer, professor of earth sciences in the USC College of Letters, Arts and Sciences, leads a research group presenting several new pieces of the P-T extinction puzzle. Matthew Clapham, a recent Ph.D. graduate of Bottjer’s laboratory, has found that species diversity and environmental changes were “decoupled” long before the extinction. Conditions on the planet were deteriorating long before species began to die off, Bottjer said, casting doubt on the meteorite strike theory. “People in the past used to think this big mass extinction was like a car hitting a wall,” he said. Instead, Clapham’s interpretation of the geological record shows “millions of years o
