For generations, books, films, and TV have warned us of the danger of mummies. In their crypts they are relatively harmless, but when they rise from the dead and start strangling people, as they did in the Cotswolds of south central England in “Doctor Who and the Pyramids of Mars,” they become a much greater threat. But this problem may shortly be solved, thanks to global warming. The world’s oldest mummies are at risk of disappearing because of man-made climate change, according to a group of Harvard University scientists. Bodies mummified about 7,000 years ago in Chile are starting to...