Narrator: This is Science Today. Sixty-five million years ago, a giant asteroid smashed into the earth, causing worldwide havoc. At around the same time, the dinosaurs, who had been around for 140 million years, went extinct. According to paleontologist Kevin Padian of the University of California, Berkeley, the asteroid had nothing to do with the extinction of the dinosaurs. Believe it or not, it was a coincidence.

Padian: The best evidence that we have from the fossil record indicates that the impact of the asteroid did almost nothing to affect terrestrial animals. The dinosaurs had already been declining for some millions of years.

Narrator: Padian says the main reason was that the earth's climate was changing. The dinosaurs couldn't adapt and quit evolving new species. By the time of the asteroid, they were already gone. Most other animals did just fine.

Padian: To test this idea, we look at the little vertebrates, we look at the snakes, the crocodiles, the turtles, the mammals, the amphibians, the fishes, the sharks. And we find that most of these groups go through this boundary without any trouble at all.

Narrator: For Science Today, I'm Steve Tokar.