On the trail of ancient killers

The newly unveiled genome of a medieval strain of the mycobacterium that causes leprosy is a technical triumph borne of next-generation sequencing machines and clever new techniques to extract target DNA from a soup of ancient molecules. Awash in data, several labs are racing neck-and-neck to cull DNA from a Most Wanted list of other legendary killers: tuberculosis, plague, cholera, Leishmania, the potato blight, and AIDS. They gather traces of these culprits from ancient teeth, bones, hair, feces, and—in the case of potato blight—from skin and leaves, then unleash the sequencers. The work adds a new dimension to our understanding of historical events, revealing the true nature of the villains responsible for humanity's worst epidemics.