New insights from the latest Denisovan fossil discovery on the Tibetan Plateau
As an extinct archaic human group which has genetically contributed to modem humans,Denisovans have received significant research interests across multiple disciplines,including archaeology,paleoanthropology,and molecular biology.However,so far,the sporadic discoveries of Denisovan fossils have limited our understanding of this hominin group.Baishiya Karst Cave site(35°27′N,102°34′12″E,3282 m above sea level),located on the northeastern margin of the Tibetan Plateau,is the only archaeological site in East Asia where Denisovan fossils have been found.It is also one of only two sites globally,besides Denisova Cave(51°23′51.3″N,84°40′34.3″E,700 m above sea level),that contains Denisovan archaeological remains.Systematic archaeological excavation and research at Baishiya Karst Cave site have revealed a continuous and long-term stratigraphic sequence and archaeological deposits from the late Middle Pleistocene to the Late Pleistocene.In-depth studies of this site not only enhance our understanding of Denisovan groups but also provide insights into their adaptation to high-altitude environments.Recently,a new Denisovan fossil(Xiahe 2)was discovered from Layer 3 of Baishiya Karst Cave site through paleoproteomic analysis,providing more hominin fossils for the study of Denisovans.Layer 3,from which the Xiahe 2 derives stratigraphically,is chronologically constrained between 48000 and 32000 years ago.Given that early modem humans had already appeared in East Asia,and even on the Tibetan Plateau,around 40000 years ago,it is crucial to directly date Xiahe 2 for gaining a more precise understanding of the occupation history of Denisovans and their potential spatiotemporal overlap at a regional scale with early modern humans.In this study,we conduct radiocarbon dating analysis of Xiahe 2 and two animal bones from the same stratigraphic layer(Layer 3)at the Baishiya Karst Cave site.Radiocarbon dating of Xiahe 2 yielded an age of 41938±303 cal a BP(mu±sigma,calendar year before present,i.e.,before AD1950;Table S1).The radiocarbon dating results of two animal bones are approximately 32000 years ago(36242±114 cal a BP)and 46000 years ago(46197±721 cal a BP)(Table S1),respectively,which are consistent with the previously determined age range for Layer 3.Although there is insufficient collagen of Xiahe 2 for further elemental analysis(C％,N％,C:N),the elemental C:N ratio of the animal bone samples,processed using the same protocol,ranged between 2.9 and 3.5,which is within the accepted margins of C:N variation.This suggests that the quality of the collagen extracted from Xiahe 2 should also be acceptable.Additionally,the consistency of radiocarbon dating results from different laboratories on the same animal bone(BSY01-18-T2-B20,OxA-39183:36570±539,and LZU20288:36242±114 cal a BP,Table S1),along with the variation in deamidation rates of bone remains at Baishiya Karst Cave site,all support the reliability of the dating results for Xiahe 2 to about 42000 years ago.These new dating results not only extend the known timeline for the latest Denisovan survival but also enrich the evidence of their presence in East Asia during the Late Pleistocene.Additionally,based on the dating results in this study,and known sites dated to 45000-40000 years ago with early modem human fossils or archaeological remains demonstrating modern human behaviours in northern China and on the Tibetan Plateau,we observe a temporal and spatial overlap between the latest Denisovan(Xiahe 2)and early modem humans in East Asia.It suggests the possibility of direct genetic exchange in the northeastern Tibetan Plateau,where Xiahe 2 was found,and surrounding regions.Therefore,our study provides new perspectives for understanding the evolutionary history of Denisovans and their interactions with early modem humans.
Denisovansmodern humansBaishiya Karst Caveradiocarbon dating
万方数据
维普
