Maybe an Asteroid Didn't Kill the Dinosaurs

When a scientific principle is common knowledge even in grammar schools, you know it's long since crossed the line from theory to established fact. That's the case with dinosaur extinction. Some 65 million years ago — as we've all come to know — an asteroid struck the Earth, sending up a cloud that blocked the sun and cooled the planet. That, in turn, wiped out the dinosaurs and made way the rise of the mammals. The suddenness with which so many species vanished after the 65-million-year mark always suggested a single cataclysmic event, and the 1978 discovery of a 112-mi., 65-million-year-old crater off the Yucatán peninsula near the town of Chicxulub seemed to seal the deal.

Now, however, a new study in the Journal of the Geological Society throws all of that into question. The asteroid impact and the dinosaur extinction, argue the authors, may not have been simultaneous, but rather may have occurred 300,000 years apart. That's an eye-blink in geological time, but it's a relevant eye-blink all the same, one that occurred at just the right moment in ancient history to have sent the extinction theory entirely awry. (Read about China's dinosaur fossils.)

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