It was 66 million years ago that dinosaurs last roamed the Earth. And for as long as man has studied their demise, the leading theory surrounding their extinction was an asteroid hitting Earth. But now, researchers think the asteroid theory is only partially correct. The primary factor in their deaths was climate change. A change in the Earth's atmospheric conditions was first triggered by a volcanic eruption, thus causing a steep drop in global temperatures. It now looks like the asteroid was the final blow...