page_title: Zhang Dongju
section_title: Research
hierarchical_section_title: Zhang Dongju / Research
caption_attribution_description: English: The lateral photograph of Xiahe mandible showing two attached molars. The mandible is the first confirmed discovery of a Denisovan fossil outside of Denisova Cave.
context_page_description: Zhang Dongju is a Chinese archeologist and an associate professor at the College of Earth and Environmental Sciences of Lanzhou University. Zhang’s research determined that the Xiahe mandible found in the Baishiya Karst Cave on the Tibetan Plateau shared DNA with fossilized remains found in the Denisova Cave in Siberia. This moved to 120,000 years earlier the dates of earliest proven hominin activities in the Tibetan Plateau, and revealed for the first time that the Denisovan hominins had spread throughout Asia rather than being located only near the Denisova Cave. Zhang’s work is considered likely to prompt reconsideration of other fossil remains using ancient protein analysis. Discover, Science News, and Nova all named the discovery to their lists of top science stories of 2019.
context_section_description: After earning her Ph.D., Zhang joined the faculty of environmental archeology at Lanzhou University. Zhang changed her research direction from the Loess Plateau to the Tibetan Plateau and began to study the Xiahe mandible, together with her former advisor Chen Fahu. The Xiahe mandible is a fossilized jawbone found in 1980 by a monk in the Baishiya Karst Cave, which is located in Xiahe County on the northeastern edge of the Tibetan Plateau, 2,250 kilometres (1,400 mi) from the Denisova Cave where the only other known Denisovan remains have been found. It was donated to Lanzhou University. According to Zhang, the mandible was so "weird" that Lanzhou researchers could not classify it, and it was overlooked for thirty years.
  Zhang investigated the original discovery of the mandible by interviewing local people in Xiahe. They confirmed human bones were found in the cave. When asked in 2019 whether it was possible the story was false, zhang said, "I don’t think the local people would lie about this.” Because the provenance is uncertain, the research team in 2019 acknowledged they could not prove the fossil came from the Baishaya cave.  But they were able to match minerals on the Xiahe mandible to mineral deposits in the cave.
  The mandible contained no productive DNA, but in the dentine of the teeth they found collagen proteins. In 2016 Zhang and colleagues started working with Jean-Jacques Hublin of the Max Planck Institute to use ancient protein analysis.
  In 2016 local villagers and Buddhists gave Zhang permission to start archeological work within the cave, which is a Buddhist sanctuary. With local permission she led a team to begin excavation in and around the cave in 2018. The team dug two trenches in which they found animal bones with cut marks and a large number of stone tools. In 2019 Zhang told Science, "We do hope we'll find more Denisovans."
caption: Xiahe mandible
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