Well-preserved specimen pushes back the timing of modern horse evolution. A group of Przewalski's horses, once considered extinct in the wild. Photograph by Michael Nichols, National Geographic Photograph courtesy D.G. Froese via Nature DNA shines a light back into the past, showing us things that fossils can't. But how far back can that light extend? Some of the oldest DNA sequences come from mastodon and polar bear fossils about 50,000 and 110,000 years old, respectively. But a new study published online today in the journal Nature reports the latest in the push for recovering ever more ancient DNA sequences. Samples...