An iconic example of the Ice Age megafauna of North America, the mammoth went extinct soon after humans arrived on the continent — except for isolated populations. WOOLLY MAMMOTH PHOTO BY STEPHEN WILKES, COURTESY OF THE ROYAL BC MUSEUM AND ARCHIVES, VICTORIA, BC, CANADA
One day thousands of years ago, on a tiny island in the middle of the Bering Sea, a woolly mammoth made a fatal misstep. It fell into a pitlike cave with no escape, and there it died. In 2003, another animal entered the cave — with a ladder. As he explored the space with his colleagues, Russell Graham, a paleontologist from Pennsylvania State University, lifted a rock near the back. There he found a single, pristine tooth from the mammoth, oblong and bumpy and as big…