A second gunman in the death of the dinosaurs?

If you’ve already heard that dinosaurs are extinct — and the betting is that you have — you’ve probably also heard the reason: an asteroid smashed into Mexico’s Yucatán Peninsula some 65 million years ago, blasting enough dust into the atmosphere to block the sunlight and dim the skies. These days that’s Intro to Dinos stuff, but prior to 1980, the thinking was very different. Dinosaurs endured a long, slow decline, the theory went, ceding their rule of the planet only gradually and grudgingly. The old theory is nearly as extinct as the beasts themselves — or at least it was until last week when a new study pumped a little life back into it. About 200,000 years before the asteroid hit, a separate extinction was already underway, wiping out numerous species of clams and snails on the ocean floor. And it was terrestrial volcanoes, not a rock from space, that were to blame…

All three of those eras coincide nicely with volcanic events in India’s Deccan Plateau, which may have belched enough carbon dioxide and other greenhouse gases to boost planetary temperatures and harm ocean-dwellers. “If this warming is severe enough to be impacting marine life it’s likely impacting terrestrial life too,” says Tom Tobin, a doctoral student at the University of Washington and the report’s lead author. “So it’s not unreasonable to think that the environmental stress from the volcanism contributed to the strength of the asteroid extinction. One of [the events] is synchronous with the marine extinction that we found 200,000 years before the asteroid impact.”