In 1980, the 160,000-year-old fossilized partial jawbone of a Denisovan — the so-called Xiahe mandible — was found in Baishiya Karst Cave, a limestone cave at the northeast margin of the Tibetan Plateau. Now, an international team of researchers has extracted genetic material from the sediments in Baishiya Karst Cave and identified mitochondrial DNA (mtDNA) from Denisovans indicating their presence at about 100,000 years ago, 60,000 years...