More than 10 years ago, scientists working in Denisova Cave-a cold site in Siberia's Altai Mountains-uncovered a strange pinky bone, broader than a typical human's. The DNA within that bone revealed that its owner belonged to an entirely new group of ancient hominins, distinct from Homo sapiens or Neanderthals. That group became known as the Denisovans. Researchers have since decoded the Denisovan genome. But still, no one can say what they looked like. Every known Denisovan fossil would fit in your palm-that pinky, three teeth, and a remarkable bone sliver from a Denisovan-Neanderthal hybrid. And all of these remains came from the same cave.
But now, an international team of scientists has announced the identification of another Denisovan fossil, from a site 1,500 miles away. It's the right half of a jawbone, found some 10,700 feet above sea level in a cave in China's Xiahe County, on the eastern edge of the Tibetan plateau. The Xiahe mandible, as it is now known, is not only the first Denisovan fossil to be found outside Denisova Cave, but also the very first Denisovan fossil to be found at all. It just took four decades for anyone to realize that.
The mandible was discovered by a local monk in 1980 and donated to Lanzhou University. There, it lay unstudied until 2010, when a team led by Fahu Chen and Dongju Zhang-a climatologist and an archaeologist, respectively-began examining it in earnest. The world learned about the existence of the Denisovans at around that time, and though fossils had only been recovered from Siberia, it was clear that these hominins likely existed throughout much of East Asia. Smatterings of Denisovan DNA still persist in the genes of living people in this region and beyond, and how else could it have made it into the genomes of modern Tibetans or Melanesians? Still, "I never imagined that [the Xiahe mandible] could be a Denisovan," Zhang says. "If it was one, we'd be so lucky,"
The molecules in the specimen were especially telling. The team couldn't detect any traces of ancient DNA, but it did find the next best thing-fragments of ancient collagen proteins, still lurking in one of the teeth. These fragments closely resemble the proteins of Denisovans, more so than those of Neanderthals, modern humans, or other great apes.
"It confirms that the Denisovans were perhaps widely distributed through East Asia," Zhang says. For years, scientists had suspected as much. After all, people across East Asia and Melanesia have Denisovan DNA in their genes. This pattern-the product of ancient sexual encounters between Denisovans and humans-shouldn't be possible if the Denisovans were just confined to a small Siberian cave. Instead, it seemed that they were already living in much of East Asia by the time ancient humans also spread through the region.
