Baishiya Karst Cave is not an easy place to call home. It is located on a steep rocky slope on the Tibetan Plateau, 10,700 feet up, where oxygen is thin and the climate cold and dry.
But a series of expeditions to the cave in recent years have shown that it was home to one of the most mysterious branches of humanity: a Neanderthal-like group of people called the Denisovans.
Since 2010, scientists have painted a fuzzy picture of the Denisovans (pronounced De-NEE-so-fugons) based on just three teeth, a few bone fragments and traces of DNA. Mystery has shrouded much of their existence, especially their behavior.
But researchers who have opened several small holes in the Baishyia Karst cave have discovered a wealth of information about the Denisovans. In a paper published Wednesday, they reported that for more than 100,000 years, Denisovans hunted or scavenged a wide range of animals on the Tibetan Plateau, from blue sheep to snow leopards and even golden eagles. Not only did the Denisovans eat the animals, but they probably skinned them to keep their clothes warm in cold temperatures.
The first evidence of Denisovans was found about 1,400 miles northwest of that country, in Denisova Cave in Siberia. DNA from a single tooth and a pinky bone showed that the group belonged to a distinct lineage from modern humans and Neanderthals.
Millions of living people carry some Denisovan genes, geneticists later discovered, indicating that modern humans interbred with them, along with Neanderthals, before both groups became extinct.
The Tibetan cave had been a Buddhist sanctuary for centuries. In 1980, a monk who came there to pray noticed part of the jaw on the ground. The specimen remained in a museum drawer for years until Dongju Zhang, an archaeologist at Lanzhou University, gave it a closer look.
The jaw looked human, but it lacked some key features, like a prominent chin. And the two molars still rooted in the bone were larger than human teeth. Dr. Zhang suspected it might be Denisovan. So she and her colleagues searched the Tibetan jawbone for DNA, without success. They had better luck when they looked for collagen proteins.
The scientists then compared the structure of the protein to the collagen genes of modern humans, Neanderthals and Denisovans. The best match was the Denisovan gene.
In 2016, Dr. Zhang began leading expeditions into the cave to learn more. On the most recent visits, her team drilled a pair of holes six meters down into the cave floor.
The expeditions revealed that the jaw must have been over 160,000 years old. The sediment also yielded four fragments of Denisovan DNA. The oldest came from a layer that formed approximately 100,000 years ago, and the youngest from a layer that formed between 48,000 and 32,000 years ago.
If this were true, it would raise the tantalizing possibility that modern humans and Denisovans had contact on the Tibetan Plateau. Archaeologists have found stone blades elsewhere on the plateau that are at least 30,000 years old and recognizable to modern humans.
While Dr. Zhang and her colleagues dug deeper, the researchers also found thousands of bone fragments in the holes. But they had no idea what species the hit pieces belonged to.
The researchers dug through the samples and found enough collagen to identify 2,005 bones.
One of them, a rib fragment, contained collagen from a Denisovan. The rib came from the same sediment layer that yielded the latest Denisovan DNA.
Samantha Brown, an anthropological scientist at the University of Tübingen in Germany, who was not involved in the study, said that finding DNA and ribs in the same layer strongly supported the existence of Denisovans so recently in Tibet.
“This is such an exciting discovery,” she said. “Without these multiple lines of evidence, it might have felt too good to be true.”
But Tom Higham, an archaeological scientist at the University of Vienna, said it was unfortunate that Dr. Zhang had been unable to find any DNA on the ribs, nor did they find carbon that they could use to accurately determine her age. “To me, it’s a significant failure,” he said.
Dr. Zhang and her colleagues concluded that the other 2,004 bones mostly belonged to animals that the Denisovans brought to the cave. Many of them show cut marks that indicate they have been butchered.
Denisovans seem to have favored blue sheep, a species that still lives today on the Tibetan Plateau. But the Denisovans also hunted or scavenged carnivores and birds of prey. They also weren’t above killing marmots, cat-sized rodents that hibernate.
Frido Welker, a molecular anthropologist at the University of Copenhagen and one of Dr. Zhang said evidence at the Baishiya Karst Cave showed that Denisovans were successfully adapting to the Tibetan Plateau even during the Ice Age.
“The Denisovans were not there by chance on a random day,” he said. “They managed to hang in there for a lot longer, which says something about their resilience.”