A new study has revealed that Denisovans survived on the Qinghai-Xizang Plateau as late as 48,000–32,000 years ago, by butchering and consuming a diverse range of animals. This study, published in Nature and led by ZHANG Dongju from Lanzhou University, Frido Welker from the University of Copenhagen, and CHEN Fahu from the Institute of Tibetan Plateau Research of the Chinese Academy of Sciences, sheds light on Denisovan behavior and demonstrates how adaptable Denisovans were to the harsh and variable environment of the Qinghai-Xizang Plateau.

The Denisovans are an extinct species of ancient human, closely related to Neanderthals, who ranged across much of eastern Eurasia towards the end of the last ice age. The researchers studied more than 2,500 bones from the Baishiya Karst Cave on the high-altitude Qinghai-Xizang Plateau, one of only two places where Denisovans are known to have lived.

Most bone fragments excavated from the Baishiya Karst Cave are so fragmented that it is impossible to morphologically identify which species they are from. A proteomic screening method called Zooarchaeology by Mass Spectrometry (ZooMS) was therefore employed. It helped the researchers determine the species of most bone specimens based on small differences in the amino acid sequence of the protein collagen.

"ZooMS allows us to extract valuable information from often overlooked bone fragments, providing deeper insight into human activities," said Dr. XIA Huan from Lanzhou University. 

By combining molecular and traditional zooarchaeological analysis, the researchers determined that most of the bones were from blue sheep (also known as bharal), which is a species of caprine common to the Himalayas today. Other bone fragments came from large herbivores—such as wild yak, equids, and the extinct woolly rhino—and carnivores—such as the locally extinct spotted hyena. They also identified bone fragments from small mammals, such as marmots, and birds.  

Together, the animal species found in the Baishiya Karst Cave indicated that the area around the cave was dominated by a grass landscape with some small forested areas.

"Large amounts of bone remains were found in the cave. The diverse species identified partly answers the questions why Denisovans chose to live in the Baishiya Karst Cave and the surrounding Ganjia Basin, and how they survived there for hundreds of thousands of years," Prof. ZHANG said.

Many of the identified bone fragments showed cut marks and other traces of human activity, indicating that they had been processed by Denisovans. Detailed analysis of the bone surfaces revealed carcass processing evidence of Denisovan such as the removal of meat and extraction of bone marrow, preparation of animal hides, and even the use of bones as tool-making materials. The bones of the small mammals and birds also showed evidence of Denisovan activity.

"Current evidence suggests that it was Denisovans, not any other human groups, who occupied the cave and made efficient use of all the animal resources available to them throughout their occupation," said Dr. WANG Jian from Lanzhou University.

In addition, the researchers found a hominin rib bone using ZooMS analysis. Detailed shotgun proteomic analysis of all the proteins preserved in the bone revealed it to be a Denisovan fossil.

"Since we only know the Denisovans from a few fossils worldwide, they are still a bit of a mystery. Every new individual we discover therefore provides a significant piece to the puzzle of who they were, where they were living, and when!" said Dr. Zandra Fagernäs from the University of Copenhagen.

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.

Collectively, the findings suggest that Denisovans lived at the Baishiya Karst Cave well into the Late Pleistocene.

"The long occupation of Denisovans at Baishiya Karst Cave, from the late Middle Pleistocene to the late Late Pleistocene, provides a good base for them to adapt to the high elevation environment characteristic of the Qinghai-Xizang Plateau," said Prof. CHEN.

Dr. Welker noted that Denisovans were on the plateau during two cold ice ages, and during a warmer interglacial period in between.

"The fossil and molecular evidence therefore indicated that Ganjia Basin where Baishiya Karst Cave is located, provides a relatively stable environment for Denisovans, despite its high altitude. The question now arises when and why these Denisovans on the Qinghai-Xizang Plateau went extinct," said Dr. Welker.

View of the Ganjia Basin where Baishiya Karst Cave is located. (Image by ZHANG Dongju's group from Lanzhou University) 

Many of the bones recovered from Baishiya Karst Cave, like this spotted hyena atlas, contain traces of human activities such as cut marks. (Image by ZHANG Dongju's group from Lanzhou University)

Xiahe 2, a Denisovan rib fragment identified through palaeoproteomic methods from Baishiya Karst Cave. (Image by ZHANG Dongju's group from Lanzhou University)