Woolly mammoths were icons of the Ice Age. Starting 700,000 years ago to just 4,000 years ago, they trundled across the chilly steppe of Eurasia and North America. As ancient glaciers expanded across the Northern Hemisphere, these beasts survived the rapidly cooling temperatures with cold-resistant traits, a characteristic they came by not through evolution, as earlier thought. Woolly mammoths, a new Nature study finds, inherited the traits that made them so successful from a mammoth species closer to a million years old.
