Bone remains found in a Tibetan cave 3,280 metres above sea level indicate an ancient group of humans survived here for many millennia, according to a new study published in the journal Nature.  The Denisovans are an extinct species of ancient human that lived at the same time and in the same places as Neanderthals and Homo sapiens. Only a handful of Denisovan remains have ever been discovered by archaeologists. Little is known about the group, including when they became extinct, but evidence exists to suggest they interbred with both Neanderthals and Homo sapiens. 

The scientists identified one rib bone as belonging to a new Denisovan individual. The layer where the rib was found was dated to between 48,000 and 32,000 years ago, implying that this Denisovan individual lived at a time when modern humans were dispersing across the Eurasian continent. The results indicate that Denisovans lived through two cold periods, but also during a warmer interglacial period between the Middle and Late Pleistocene eras. 

The research team studied more than 2,500 bones from the Baishiya Karst Cave on the high-altitude Tibetan Plateau, one of the only two places where Denisovans are known to have lived. Their new analysis has identified a new Denisovan fossil and shed light on the species’ ability to survive in fluctuating climatic conditions — including the ice age — on the Tibetan plateau from around 200,000 to 40,000 years ago. 

Bone remains from Baishya Karst Cave were broken into numerous fragments preventing identification. The team used a novel scientific method that exploits differences in bone collagen between animals to determine which species the bone remains came from.  The research team determined that most of the bones were from blue sheep, known as the bharal, as well as wild yaks, equids, the extinct woolly rhino, and the spotted hyena. The researchers also identified bone fragments from small mammals, such as marmots, and birds. The team was able to identify that Denisovans hunted, butchered and ate a range of animal species.

Detailed analysis of the fragmented bone surfaces shows the Denisovans removed meat and bone marrow from the bones, but also indicate the humans used them as raw material to produce tools.  

An undated artist’s impression of members of the extinct archaic human species called the Denisovans seen in the landscape of Ganjia Basin on the northeastern edge of the Tibetan Plateau in China’s Gansu province, depicting some of the animals whose bones were found at Baishiya Karst Cave.
| Photo Credit: Reuters

Thousands of bone fragments discovered in a cave on the Tibetan Plateau in China are offering rare insight into the lives of Denisovans, the mysterious extinct cousins of Neanderthals and our own species, showing they hunted a wide range of animals from sheep to woolly rhinoceros in this high-altitude abode.

Researchers studied more than 2,500 bones found inside Baishiya Karst Cave, which is situated 10,760 feet (3,280 meters) above sea level and previously had yielded Denisovan fossil remains.

They used ancient protein analysis on these remains to reveal that the Denisovans exploited various animals for their meat and skins, and also excavated and identified a rib bone from a Denisovan individual dating to 48,000-32,000 years ago – the youngest Denisovan fossil yet known.

Most of the bones were identified as belonging to blue sheep, also called bharal, a goat species still seen on high slope mountains and cliffs in the Himalayas. Other bone remains came from woolly rhinos, yaks, small mammals like marmots, birds, and even from the spotted hyena, a large carnivore that prowled the region called the Ganjia Basin.

It was a grass landscape with small forested areas, teeming with life despite harsh conditions. The animals were butchered for meat, based on cut marks found on various bones, and there was evidence of bone marrow extraction and skinning activities. The researchers also found four tools fashioned from animal bone, shaped for use in processing animal carcasses.

“It is the first time we have gotten an understanding of the subsistence behaviors of Denisovans, and it shows us they were highly capable of accessing and utilizing a wide range of animal resources,” said University of Copenhagen molecular anthropologist Frido Welker, one of the leaders of the research published on Wednesday in the journal Nature.

“I think the diverse animal remains found in Baishiya Karst Cave suggest that this location offered relatively better resources compared with the neighboring higher Tibetan Plateau to the west and the Chinese Loess Plateau to the north, especially in the glacial period,” said archeologist Dongju Zhang of Lanzhou University in China, another of the study leaders.

The existence of Denisovans was unknown until researchers in 2010 announced the discovery of their remains in Denisova Cave in Siberia, with genetic evidence showing them to be a sister group to Neanderthals, the stoutly built extinct archaic humans who inhabited parts of Eurasia. Both experienced significant interactions with Homo sapiens, including interbreeding, before vanishing soon after for reasons not fully understood.

“From genetics, we know they diverged from Neanderthals around 400,000 years ago,” Welker said.

Denisovans are known only from dental remains and bone fragments from the Baishiya Karst and Denisova caves and Cobra Cave in Laos, though their existence at those three far-flung locations demonstrates a wide geographic dispersal.

Their presence at a high latitude in Siberia, a high altitude on the Tibetan Plateau and a subtropical location in Laos “implies that Denisovans had high flexibility to adapt to different environments,” Zhang said.

A lower jaw of a Denisovan adolescent previously found at Baishiya Karst is 160,000 years old. The researchers suspect Denisovans were present there as far back as 200,000 years ago. The newly identified rib fragment shows that Denisovans still existed as recently as 48,000-32,000 years ago.

“We don’t know if the rib was from an adult or a child, nor its genetic sex. It is the first time a rib specimen has been identified as a Denisovan. Previous remains are all dental or cranial or mandibular (lower jaw),” Welker said.

Our species, Homo sapiens, did not populate the Tibetan Plateau until about 40,000 years ago, having first appeared in Africa a bit more than 300,000 years ago.

So what happened to the Denisovans?

“Great question. We know so little,” Welker said. “We know that Denisovans interbred with modern humans. We know that based on some Denisovan DNA that is present in the genomes of some modern humans living today. But when, where and why Denisovans ultimately went extinct, that we don’t know anything about.”