Nearly every species that has lived on earth is extinct. The last of the dinosaurs was wiped out after a Mount Everest-sized meteorite slammed into the earth 65 million years ago. The great flying and marine reptiles are no more. Before humans crossed the Bering Land Bridge some 15,000 years ago, North America was populated by mastodons, mammoths, saber-toothed tigers, and cave bears. They too are MIA. The passenger pigeon, once the most numerous bird in North America, is gone forever. In No Turning Back , renowned naturalist Richard Ellis explores the life and death of animal species, immortalizing creatures that were driven to extinction thousands of years ago and those more recently. He documents those that were brought back from the brink, and most surprisingly, he reveals animals not known to exist until the twentieth century -- an antidote to extinction.