DNA z-bo 2020-11-02 357

　　Denisovans are a newly discovered group of ancient humans. They are a sister group to Neanderthals who were once widely distributed in Europe. They have genetic contributions to modern Oceania, East Asia, South Asia and Native American populations, and are of widespread concern. Research hotspots.

　　Previously, a research team led by Lanzhou University and the Institute of Tibetan Plateau Research of the Chinese Academy of Sciences reported on the Xiahe mandibular fossil found in the Baishiya cave in the northeast of the Qinghai-Tibet Plateau and identified it as a Denisovan using ancient protein analysis. And using uranium dating methods to determine its age as at least 160,000 years ago. However, the Xiahe fossil was identified as Denisovan mainly based on an amino acid change in the ancient protein, and the fossil lacks information on buried strata and coexisting archaeological remains. Therefore, although the fossil promoted prehistoric human activities on the Qinghai-Tibet Plateau and Denisovan The research on the Wa people, but the information revealed about the Denisovans distributed on the Qinghai-Tibet Plateau is relatively limited. For example, little is known about their temporal and spatial distribution, genetic characteristics, and cultural connotations. In order to understand the living conditions of the people represented by the mandibles of the Xiahe people on the Qinghai-Tibet Plateau, since 2010, the Lanzhou University environmental archaeology team led by Chen Fahu, an academician of the Chinese Academy of Sciences and a researcher at the Qinghai-Tibet Plateau Institute, has carried out activities in the Baishiya Karst Cave and its Ganga Basin. Archaeological investigation and research work. In 2018, an environmental archaeology team led by Zhang Dongju, a professor of Lanzhou University and a guest researcher of the Qinghai-Tibet Plateau Earth Science Excellence Innovation Center of the Chinese Academy of Sciences, conducted archaeological excavations of the Baishiya cave site and invited multiple research teams to conduct multidisciplinary comprehensive research.

　　Recently, the research team has made progress in the study of Baishiya karst cave and found that the Baishiya karst cave site has preserved more Middle Pleistocene and Late Pleistocene ancient human activities, and obtained the mitochondrial genes of Denisovan people outside Denisowa Cave The sequence reveals that Denisovans lived on the Qinghai-Tibet Plateau for a long time in the late Pleistocene. The excavation and research work of the research team showed that the site has a continuous layer of Paleolithic culture and rich archaeological remains of the Paleolithic, including a large number of stone products and skeletal remains. Multi-index analysis of sediments shows that the stratum accumulation is mainly primary accumulation, and the archaeological remains have not been significantly disturbed. Generally, the source and transportation of cave sediments are complicated, and it is difficult to accurately date. The research team selected 14 animal bones for AMS14C dating on layers 1-6, and found that the bones on layers 4-6 had exceeded the upper limit of 14C dating. At the same time, 12 optical luminescence samples were collected on layers 2-10. Combined with the results of AMS14C and optical luminescence dating, a Bayesian age model was established to establish an age frame of ~19-~30,000 years for the site.

　　Sediment DNA analysis is a kind of ancient DNA analysis technology. Archaeological site sediments can track the DNA preservation status of related sites and the possible existence of ancient humans, expand the research object, and open a new window to study the population evolution of paleolithic archaeological sites. Before the excavation of the site, the research team and Fu Qiaomei, a researcher at the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, carried out sediment DNA analysis. Zhang Dongju and Fu Qiaomei formulated a sampling plan for sediment samples for ancient DNA analysis to ensure the sample collection and transportation process China will not be polluted by modern humans. In order to identify and isolate the target DNA from the DNA of massive environmental microorganisms, Fu Qiaomei's team tried to collect 35 samples of mitochondrial DNA of 242 mammals and humans through ancient DNA capture technology, and enriched the DNA of ancient humans. . Analysis shows that the ancient DNA of animals in the sediments, including extinct animals such as rhinos and hyenas, is consistent with the remains of animal bones found at the site. This time, they were found in the Xiahe County area to broaden the understanding of the habitat of extinct animals. Fu Qiaomei’s team used 54 different modern humans, 23 Neanderthals, 4 Denisovans, and a 400,000-year-old ancient human Sima individual’s mitochondrial genomes to distinguish between modern humans and Neanderthals. On this basis, it is clear that there are mitochondrial DNA of the ancient human Denisovan in the four strata of Baishiyadong. Through analysis, except for a few samples, most of the stratum samples were not contaminated by modern human DNA.

　　In addition, various calculations such as unique genetic mutations have shown that there are multiple individual DNAs in soil sediment samples, and it is difficult to calculate the age of related samples through tip dating. Therefore, the sample age can only be inferred based on the results of stratigraphic dating. It is estimated that the Denisovan DNA of three of these strata mainly appeared around 30,000 to 50,000 years ago (stratum 2 and 3) and 60,000 to 70,000 years ago (stratum 4). Through the analysis of the mitochondrial DNA phylogenetic tree, the ancient human DNA in these strata (2, 3, 4) is closely related to the late Denisovans (Denisova 3 and Denisova 4) from the Denisova caves in the Altai Mountains of Russia. Genetic link. In contrast, the mitochondrial DNA analysis of the Denisovans in the formation (stratum 7) dating from about 100,000 years ago showed that they were separated from the late Denisovans at an earlier time. The discovery of Denisovans outside the Denisovan Cave this time is evidence supporting the widespread distribution of Denisovans. Based on the latest research results of Xiahe mandibular fossils and Baishiya cave, it is found that the Denisovans lived on the Qinghai-Tibet Plateau from the penultimate to the last glacial period, and are closely related to the late Denisovans in the Altai Mountains. The genetic connection further confirms that Denisovans were once widely distributed on the eastern side of Eurasia.

　　The latest research results of the Baishiya Karst Cave provide stratigraphic, archaeological, chronological and genetic evidence for the activities of the Denisovans at the Baishiya Karst cave site, as well as to understand the time and space distribution, genetic characteristics, and culture of the Denisovans. Researches on characteristics and environmental adaptation provide scientific basis, and are of great significance to reconstruct the history of ancient human activities on the Qinghai-Tibet Plateau and clarify the evolution history of ancient humans in East Asia. Related research results are published on Science. Zhang Dongju is the first author of the paper. Zhang Dongju, Fu Qiaomei, Li Bo, associate professor at the University of Wollongong in Australia, and Svante Paabo, professor at the Max Planck Institute for Evolutionary Anthropology in Germany, are the co-corresponding authors.