This story was originally published in Undark and appears here as part of the Climate Desk collaboration. In 1823, the chief surgeon at Massachusetts General Hospital, John Warren, prepared to autopsy a 2,500-year-old corpse. Warren figured examining the Egyptian mummy—a gift from a patron that had been placed in the hospital’s surgical ward to collect quarters from gawkers—would advance knowledge of the ancients. He carefully began cutting through the old linen, and then stopped. He had exposed a blackened but exquisitely preserved head: high cheekbones, wisps of brown hair, gleaming…