The worst extinction in our planet's history, and what it means for…

The mass extinctions that wiped out the dinosaurs aren't the worst in our planet's history, Paul Gilster explains. The absolute worst extinction event occurred around 2.4 billion years ago. » 7/02/10 2:30pm 7/02/10 2:30pm

Why did nearly all life on Earth die 250 million years ago?

Among paleontologists, it's sometimes called the "Great Dying." Roughly a quarter of a billion years ago, 90-95 percent of all life on Earth died out. It took 30 million years for the planet to recover. What happened? » 6/09/10 7:44pm 6/09/10 7:44pm