Earth's mass extinctions: Peter Ward on TED.com

Asteroid strikes get all the coverage, but "Medea Hypothesis" author Peter Ward argues that most of Earth's mass extinctions were caused by lowly bacteria. The culprit, a poison called hydrogen sulfide, may have an interesting application in medicine. (Recorded February 2008 in Monterey, California. Duration: 19:42.)
About Peter Ward
Peter D. Ward studies life on Earth -- where it came from, how it might end, and how utterly rare it might be.