Dietary diversity of Denisovans on the Tibetan Plateau
New research sheds light on Denisovan behaviour and indicates how adaptable they were to the harsh and variable environment of the Tibetan 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. A research team led by Frido Welker from the Globe Institute, University of Copenhagen, Dongju Zhang from Lanzhou University (China) and Fahu Chen from the Institute of Tibetan Plateau Research, CAS (China) studied more than 2,500 bones from the Baishiya Karst Cave on the high-altitude Tibetan Plateau, one of only three places where Denisovans are known to have lived.
Proteomics for zooarchaeology
Most bone fragments excavated from Baishiya Karst Cave are so fragmented that it is impossible to morphologically identify which species they are. The team therefore employed a proteomic screening method, named Zooarchaeology by Mass Spectrometry (ZooMS). Based on small differences in the amino acid sequence of the protein collagen, ZooMS was able to help the researchers determine the species of most bone specimens. “ZooMS allows us to extract valuable information from often overlooked bone fragments, providing deeper insight into human activities.” Dr. Huan Xia said (Lanzhou University), who conducted part of the proteomics research while based at the University of Copenhagen as a PhD student.
Fauna community composition
By combining molecular and traditional zooarchaeological analysis, they determined that most of the bones were from blue sheep (also known as the bharal), which is a species of caprine common to the Himalayas today. Other bone fragments came from large herbivores, such as the wild yak, equids and the extinct woolly rhino, and carnivores, such as the locally extinct spotted hyena. The researchers also identified bone fragments from small mammals, such as marmots, and birds. Together, the animal species found in Baishiya Karst Cave indicate that the area around the cave was dominated by a grass landscape with some small forested areas.
Many of the bones recovered from Baishiya Karst Cave, like this spotted hyena vertebra, contain traces of human activities such as cut marks. Credit: Dongju Zhang’s Group (Lanzhou University)
Denisovan activities
Many of the identified bone fragments had cut-marks and other traces of human activities, indicating that they had been processed by Denisovans in the past. Detailed analysis of the human activities visible on the bone surfaces show both the removal of meat and extraction of bone marrow, but also indicate the preparation of animal hides, and even the use of bone as tool-making materials. There are also human activities visible on the bones of the small mammals and birds. Together, this shows that the inhabitants of the cave made efficient use of all animal resources available to them.
Xiahe 2, a Denisovan rib fragment identified through palaeoproteomic methods from Baishiya Karst Cave. Credit: Dongju Zhang’s group (Lanzhou University)
A new Denisovan fossil
In addition, through the ZooMS analysis the researchers found a hominin rib bone. Detailed shotgun proteomic analysis, conducted in collaboration with Prof. Jesper V. Olsen from the Novo Nordisk Center for Protein Research (SUND), of all the proteins preserved in this 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” Dr. Zandra Fagernäs says (postdoctoral researcher at Globe Institute, UCPH). The layer where the rib was found was dated to between 48,000 and 32,000 years ago, implying that this rib is the youngest Denisovan fossil discovered to date and that this Denisovan individual lived at a time when modern humans were dispersing across the Eurasian continent.
Collectively, the results suggest that Denisovans lived at Baishiya Karst Cave well into the Late Pleistocene. "Denisovans were there during two cold ice ages, but also during a warmer interglacial period in between. Together, the fossil and molecular evidence therefore indicates that Ganjia Basin, where Baishiya Karst Cave is located, provided a relatively stable environment for Denisovans, despite its high-altitude", adds Associate Professor Frido Welker, "The question now arises when and why these Denisovans on the Tibetan Plateau went extinct".
The paper "Middle and Late Pleistocene Denisovan subsistence at Baishiya Karst Cave" is published in Nature.
Contact
Associate Professor Dr. Frido Welker
Mail: frido.welker@sund.ku.dk
Phone: +45 35 32 64 22