An article published in the journal “Nature” reports the results of a study of over 2,500 fossils found in the Baishiya Karst Cave, in the Chinese region of Xiahe, on the Tibetan plateau, among which a partial rib (Top image courtesy Dongju Zhang’s group (Lanzhou University)) attributed to a Denisovan. A team of researchers used an analysis technique called Zooarchaeology by Mass Spectrometry (ZooMS) to attribute isolated and often fragmented bones to the right species through collagen characteristics. According to the researchers, the Denisovans may have lived in that cave between 200,000 and 40,000 years ago.
For several years, the Denisovans were known literally thanks to a few bones discovered in Denisova Cave, Siberia. The excellent preservation of those bones preserved DNA fragments and allowed genetic analyzes to be conducted which convinced the authors that they belonged to a species separate from Homo sapiens and Neanderthal but closely related to both.
In 2019, an article published in the journal “Nature” reported evidence that a jawbone discovered in the Baishiya Karst Cave belonged to a Denisovan, the first one identified outside Siberia. The research in the Tibetan cave continued with the analysis of bones of many different species for a total of over 2,500 fossils with very interesting results.
The ZooMS technique is the archaeological application of a technique that was developed to distinguish isolated or fragmented bones of similar animal species that make identification based on their anatomical characteristics alone difficult if not impossible. The peptide sequences in collagen are like fingerprints that allow to recognize the species a bone belongs to. In the archaeological field, it often happens that isolated or even fragmented bones are found, therefore if they are well preserved, the ZooMS technique can be invaluable for research.
In the case of the bones discovered in the Baishiya Karst Cave, the ZooMS technique made it possible to recognize several animal species even if they were very fragmented. Among the species identified are the blue sheep, known as bharal, as well as wild yaks, equids, the extinct woolly rhino, the spotted hyena, marmots, and birds.
However, the most intriguing discovery is that of a partial rib that was attributed to a Denisovan and cataloged as Xiahe 2. The layer in which the rib was found was dated between 48,000 and 32,000 years ago, a time in which Homo sapiens were spreading across Eurasia. The jawbone described in the study published in 2019, cataloged as Xiahe 1, is approximately 160,000 years old.
According to the researchers, the Denisovans may have survived passing through a few climate changes in Tibet between 200,000 and 40,000 years ago, perhaps even up to 30,000 years ago. Slaughter marks present on many animal bones such as those in the bottom image (Courtesy Xia, H., Zhang, D., Wang, J. et al. Middle and Late Pleistocene Denisovan subsistence at Baishiya Karst Cave. Nature (2024)) indicate that the Denisovans hunted and slaughtered various species.
This study of the fossils found in the Baishiya Karst Cave increases our knowledge of the Denisovans but we still know very little about this species. The authors wondered when and how the Tibetan population of Denisovans became extinct but it’s also possible that it interbred with the Homo sapiens who had arrived in that region in the meantime. Among Asian populations, the presence of Denisovan genes proved to be common and the history of interbreedings between the two species represents another part of the history of humanity.
