Sequencing the dead to save the living

Genes tell stories of disease, of health, of parentage, all recorded in the chemical composition of DNA. But to many biologists, one of the most exciting tales that sequences of DNA letters can tell is an evolutionary one. And since evolution on its largest scale—the shifting cast of organisms populating Earth over the past few billion years—happens over lengthy periods of time, some of the best stories may be locked in the DNA of species long buried and gone extinct.