Some scientists challenge the meteor impact theory as the cause of the extinction of the dinosaurs. This program lays out the evidence and considers alternative explanations. The program also points out that many of the plant animal families that are in danger now survived the KT extinction suggesting the beginning of a new mass extinction. But even if we avoid a mass extinction changing climatic cycles will give humans trouble in 10,000 years when a new ice age cause glaciers to expand all over the Earth. Or, for North Americans, the Yellowstone super volcano is overdue to eruption.—David Foss