No Turning Back: The Life and Death of Animal Species

Nearly every species that has lived on earth is extinct. The last of thedinosaurs was wiped out after a Mount Everest-sized meteorite slammedinto the earth 65 million years ago. The great flying and marine reptiles areno more. Before humans crossed the Bering Land Bridge some 15,000 yearsago, North America was populated by mastodons, mammoths, saber-toothedtigers, and cave bears. They too are MIA. The passenger pigeon, once themost numerous bird in North America, is gone forever.

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