This title describes a walk with a dinosaur, as two teams of scientists race to bring back to life the long-extinct woolly mammoth, using DNA from a frozen mammoth discovered in a cliff face in Northern Siberia. Advances in medical and scientific technology mean that the impossible is now theoretically possible: a mammoth can be cloned from a frozen, long-dead mammoth corpse. But it's not easy. No one knows for sure how long frozen mammoth sperm keeps. Elephant sperm keeps well, but the mammoth has been extinct for at least 4000 years. But the mammoth remains a vividly real image: huge, with great curving tusks it is both utterly familiar and completely unknown.