Seeking the deadly roots of the dinosaurs' ascent
Monday, August 20, 2012 - 06:50
in Paleontology & Archaeology
Over the past 450 million years, life on earth has undergone at least five great extinctions, when biological activity nosedived and dominant groups of creatures disappeared. The final one (so far) was 65 million years ago, when it appears that a giant meteorite brought fires, shock waves and tsunamis, then drastically altered the climate. That killed off the dinosaurs, setting the stage for mammalsand eventually usto evolve. Many scientists are now starting to think we are on the edge of a sixth extinctionthis one driven by human destruction of other species and their habitats, and our quickening releases of carbon dioxide into the air, which threatens to bring another round of rapid climate change.