More than 50,000 years ago, a den in sandy soil collapsed on a wolf pup and killed her, sealing her away from air and moisture so the pup’s body mummified in the cold. She stayed buried in permafrost until four years ago, when the work of global warming and the explorations of a gold miner uncovered her in Canada’s Yukon Territory near Dawson City. The puppy is so well preserved that it is easy to tell from visual observation that she is female. 