with Cd and significant contamination with Zn. Interestingly, the samples contaminated with Cd included the cluster I and II samples, meaning the source of Cd contamination had agreed with the results of n-alkanes. The combined evaluation of n-alkanes and heavy metals suggested that their pollutant sources were crude oil contamination.

Zhang, D., Xia, H., Cheng, T., Chen, F., 2020. New portraits of the Denisovans. Science Bulletin 65, 1-3.

http://www.sciencedirect.com/science/article/pii/S209592731930595X Denisovans, well known for their high-coverage genetic sequences, are considered to be a new human species genetically distinct from Neanderthals and modern humans [1]. As a close sister group of Neanderthals, Denisovans not only interbred with Neanderthals [2], but they also contributed genetically to extant humans, including modern populations in parts of Oceania and Asia, aboriginal Americans and high-altitude modern Tibetans [3], [4], [5]. This implies that Denisovans probably were once widespread in eastern Eurasia and Oceania, and that they also interbred with modern humans. Therefore, Denisovans probably have played an important role in human evolution in East Asia. However, due to the limited and fragmentary fossil record of Denisovans (Denisova 2, Denisova 3, Denisova 4, Denisova 8) (Fig. 1c), which is found only at Denisova Cave (Altai, Russia; 700 ma.s.l., meters above sea level; Fig. 1a) and obscure chronological issues regarding both human fossils and cave sediments, we know very little about this extinct human species, except for its high resolution genetic information. Nature Two papers published in the January issue of by Jacobs et al. [6] and Douka et al. [8] both aim to establish a reliable chronology for human occupation in Denisova Cave. Based on stratigraphic and site formation analysis and using optical dating of 103 cave sediment samples, Jacobs et al. [6] established a long chronology for the Pleistocene sedimentary sequence and archaeological remains in Denisova Cave, and they also reconstructed the paleoenvironment in the vicinity of the site, since 350 ka (tho usand years ago). Combining this chronology with human fossils, archaeological and sedimentary DNA (deoxyribonucleic acid) evidence, they also estimated the timing of the occupation of Denisova Cave by Denisovans and Neanderthals. In addition, Douka et al. [8] built Bayesian models, based on diverse available information including cave sediment stratigraphy, the relative genetic dates of human remains, radiocarbon dates on charcoal, human fossils and animal bone artifacts, and one uranium-series date on human fossils, to estimate the ages of human fossils and the onset of the Upper Paleolithic at Denisova Cave. These two studies together provide reliable age controls for various human activities in Denisova Cave and have laid the foundation for further interpreting the relationships between Denisovans and Neanderthals, or even modern humans, at the site. According to these two studies, the oldest Denisovan fossils may have been as early as 195 ka (Denisova 2) [8], while archaeological remains and sedimentary DNAextracts indicate that the cave may have been occupied by Denisovans since around 300 ka (or, conservatively, around 200 ka) until 50 ka [6], overlapping with occupations of Neanderthals from 193 to 97 ka [8]. Therefore, Denisovans, as well as Neanderthals, in Denisova Homo Cave, were coexisting with various other neighboring unknown species of middle Pleistocene archaic sapiens (around 300 -100 ka) [9] in East Asia. The question therefore arises as to the nature of their long coexistence for nearly 200 ka (thousand years). However, without sufficient knowledge of the physical Homo sapiens morphological characteristics of Denisovans and genetic data of archaic in East Asia, this question is difficult to address. Nature A study published in in May of 2019 by us and our co-authors, reported the discovery of the right-half of a hominin mandible (Fig. 1 c) found in Baishiya Karst Cave (3200 ma.s.l.; Fig. 1b) (in Xiahe County, Gansu Province) in the northeastern Tibetan Plateau (Fig. 1a). It is identified by palaeoproteomic analysis as Denisovan, or from a Denisovan- related population, and dated to at least 160 ka by the U -series method [7]. As the evidence of the earliest hominin presence on the Tibetan Plateau, the Xiahe mandible shows that Denisovans have occupied the Tibetan Plateau since at least 160 ka, during the penultimate glacial period, 120 ka before the regional arrival of Modern Humans as indicated by the blade industry found at the Nwya Devu site (approxima tely 40 ka) [10]. We assume that the Xiahe Denisovans may have accumulated adaptive alleles as an adaptation to the extremely cold and hypoxic environments of the Tibetan Plateau, such as EPAS1 (Endothelial PAS domain-containing protein 1) found in both modern high-altitude Himalayans and the Siberian Denisovan genome [3]. More importantly, as the largest Denisovan fossil ever found (Fig. 1c) and the first Denisovan fossil discovered outside Denisova Cave, the Xiahe mandible confirms the hypothesis that