An anonymous reader writes with an excerpt from Medical Daily about a new theory for what triggered the "Great Dying: " "Researchers believe that they may finally know why the event occurred, but the theory is not without controversy. There are several theories, including the possibility of a meteorite hitting the planet. Previously, most researchers believed that the Permian mass extinction was a result of a series of volcanic eruptions in what is now Siberia. ... However, Daniel Rothman from the Massachusetts Institute of Technology is floating around a different theory. As he presented in a meeting for the American Geophysical Union, he believes that the mass extinction could have been caused by something much smaller. His theory is that the extinction was caused by a single strain of bacteria."