The oldest known mass extinction

is, as it were, a way of life. Earth’s history has seen several. The most famous, 66m years ago at the end of the Cretaceous period, did for most of the dinosaurs (only a few of the feathered variety, now referred to as “birds”, slipped through). The worst was 252m years ago between the Permian and Triassic periods, when 80% of marine species, as well as a lot of terrestrial ones, snuffed it. But the oldest? Research just published in the by Scott Evans, of Virginia Tech, and Mary Droser, of the University of California, Riverside, suggests it happened 550m years ago—a particularly intriguing conclusion because that was during a geological period, the Ediacaran, which predates the explosive diversification of animal life that got under way 539m years ago at the beginning of the Cambrian period.