"Extraordinary. . . . Berger is a hero of biology who deserves the highest honors that science can bestow."--Tim Flannery, New York Review of Books On the Tibetan Plateau, there are wild yaks with blood cells thinner than those of horses' by half, enabling the endangered yaks to survive at 40 below zero and in the lowest oxygen levels of the mountaintops. But climate change is causing the snow patterns here to shift, and with...