Until about 13,000 years ago, North America was home to a menagerie of massive mammals. Mammoths, camels, and lions walked the ground that has become Wilshire Boulevard in Los Angeles and foraged on the marsh land now buried beneath Chicago's streets. Then, just as the first humans reached the Americas, these Ice Age giants vanished forever. pIn emOnce and Future Giantsem, science writer Sharon Levy digs through the evidence surrounding Pleistocene large animal megafauna extinction events worldwide, showing that understanding this history--and our part in it--is crucial for protecting the elephants, polar bears, and other great creatures at risk today. These surviving relatives of the Ice Age beasts now face the threat of another great die-off, as our species usurps the planet's last wild places while driving a warming trend more extreme than any in mammalian history. Deftly navigating competing theories and emerging evidence, emOnce and Future Giantsem examines the extent of human inf