MOST mass extinctions were caused by gradual climate change rather than catastrophic asteroid impacts. That’s the controversial view of one palaeontologist, who says it could mean we are in the midst of a mass extinction now.
Other palaeontologists disagree, and the dispute is turning into a full-scale academic brawl. “It’s a shoot-out at the OK Corral,” says Peter Ward of the University of Washington in Seattle, who aired his climate change theory at NASA’s Astrobiology Science Conference (AbSciCon) in Washington DC last week.
Five major extinctions have occurred in the past 500 million years: the Ordovician, the Devonian, the Permian,…
