The debate was over the smaller, background extinctions that pepper the fossil record, in which 10 to 20 percent of species died out. One critical reason for wanting an answer to this question is that human activity now is eliminating many species each year in what some see as a major, human-caused extinction event. They found an average of 10 million years between an extinction and a subsequent flourishing of life. When they eliminated the five mass extinctions from that period, including the extinction 65 million years ago when the dinosaurs died out, the smaller background extinctions also averaged a 10 million-year recovery period. Weil said that the long recovery period is perhaps not surprising.
Extinction is a double whammy.
Diversification takes a long time to ramp up. Kirchner notes that their sobering findings don't necessarily imply a stark fate for the Earth. Copyright 2000, The Regents of the University of California. Produced and maintained by the Office of Public Affairs at UC Berkeley .