1 Scientific RepoRts | 6:18955 | DOI: 10.1038/srep18955 www.nature.com/scientificreports earliest tea as evidence for one branch of the silk Road across the tibetan plateau Houyuan Lu 1,2 , Jianping Zhang 1,2 , Yimin Yang 3 , Xiaoyan Yang 4 , Baiqing Xu 2,5 , Wuzhan Yang 6 , tao tong 7 , shubo Jin 8 , Caiming shen 9 , Huiyun Rao 3 , Xingguo Li 10 , Hongliang Lu 11 , Dorian Q. Fuller 12 , Luo Wang 1 , Can Wang 1 , Deke Xu 1,2 & Naiqin Wu 1,2 phytoliths and biomolecular components extracted from ancient plant remains from Chang’an (Xi’an, the city where the silk Road begins) and Ngari (Ali) in western tibet, China, show that the tea was grown 2100 years ago to cater for the drinking habits of the Western Han Dynasty (207BCE-9CE), and then carried toward central Asia by ca.200CE, several hundred years earlier than previously recorded. the earliest physical evidence of tea from both the Chang’an and Ngari regions suggests that a branch of the silk Road across the tibetan plateau, was established by the second to third century Ce. Tea (Camellia sinensis L.) is one of the most popular nonalcoholic beverages, consumed by over two-thirds of the world’s population for its refreshing taste, aroma, medicinal, and mildly stimulating qualities 1 . he exact antiquity of tea is shrouded in Chinese myth 2 . he irst unambiguous textual reference to the consumption of tea as a bev- erage can be dated to 59 BCE during the Western Han Dynasty 2,3 . However, its widespread popularity amongst both northern Chinese and people to the west such as Uighurs is generally attributed to the Tang Dynasty (7 th –8 th century CE) 4 . Previously the oldest physical evidence of tea was from China’s Northern Song Dynasty (960–1127 CE) 5 . It has long been hypothesized that tea, silks and porcelain were key commodities exported from the ancient Chinese capital, Chang’an, to central Asia and beyond by caravans following several transport routes constituting the network commonly referred to as the Silk Road 6–10 , in use by the second century BCE. However, there are no records of tea having been carried along the Silk Road into Tibet, central Asia or southern Asia until the Tang Dynasty (618–907 CE) 6,7 . he Tibetan Plateau was then closely linked eastwards to central China through trade of tea and horses for Tibetan furs and medicinal plants 6–10 . Although trade of millets already connected the Tibetan Plateau to lowland China more than 4000 calibrated years before present (yr BP) 11 , and barley cultivation and pastoralism expanded ater 3600 yr BP 12 , the emergence of historical patterns of commodity trade and habits of tea drinking along the Silk Road and in the Tibetan Plateau has remained poorly understood, due mainly to the poor preservation of plant leaves, and the challenge of identifying decayed tea remains in archeological samples 7,13 . Here, we present evidence from calcium phytoliths (calcium oxalate plant crystals), chemical biomarkers and radiocarbon dating from dried plant bundles from two funerary sites: the Han Yangling Mausoleum 14 in Xi’an, Sha’anxi Province; and the Gurgyam Cemetery in Ngari district, western Tibet 15,16 (Fig. 1a). Large modern ref- erence collections are used to compare and contrast microfossil morphology and biomolecular components of these ancient remains to modern standards of tea and related plant species 13 . Our study reveals that tea was drunk by Han Dynasty emperors as early as 2100 yr BP and had been introduced into the Tibetan Plateau by 1800 yr BP. his indicates that one branch of the Silk Road passed through western Tibet at that time. 1 Key Laboratory of cenozoic Geology and environment, institute of Geology and Geophysics, chinese Academy of Sciences, Beijing 100029, China. 2 center for excellence in tibetan Plateau earth Science, chinese Academy of Sciences, Beijing 100101, China. 3 University of Chinese Academy of Sciences, Beijing 100049, China. 4 institute of Geographic Sciences and Natural Resources, Chinese Academy of Sciences, Beijing 100101, China. 5 institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China. 6 Shaanxi Provincial institute of Archaeology, Xi’an 710001, China. 7 Institute of Archaeology, Chinese Academy of Social Sciences, Beijing 100710, China. 8 Ministry of Industry and Information Technology, Beijing 100804, China. 9 Key Laboratory of Plateau Lake Ecology and Global Change, Yunnan Normal University, Kunming 650092, China. 10 Ali district culture bureau of Tibet, Ali 859000, China. 11 Center for Tibetan Studies of Sichuan University, Chengdu 610064, China. 12 institute of Archaeology, University College London, 31-34 Gordon Square, London WC1H 0PY, U.K. Correspondence and requests for materials should be addressed to H.Y. L. (email: houyuanlu@mail.iggcas.ac.cn) received: 26 June 2015 Accepted: 02 December 2015 Published: 07 January 2016 opeN