A revolution is underway in archaeology. Working at the cutting edge of genetic and molecular technologies, researchers have been probing the building blocks of ancient life-DNA, proteins, fats-to rewrite our understanding of the past. Their discoveries (including a Mitochondrial Eve, the woman from whom all modern humans descend) and analyses have helped revise the human genealogical tree and answer such questions as: How different are we from the Neanderthals? Who first domesticated horses and ancient grasses? What was life like for our ancestors? Here is science at its most engaging.