Traces of fossilized dental calculus on the only surviving molar have helped solve the mystery of one of Asia's most valuable palaeontological discoveries. A nearly complete skull, found in China's Heilongjiang province and nicknamed the "dragon man," belonged to a Denisovan, a member of an extinct human lineage related to the Neanderthals.
This conclusion was reached by the authors of two molecular studies, published in the journals Cell and Science. One group of scientists, led by Qiaomei Fu of the Institute of Vertebrate Paleontology and Paleoanthropology of the Chinese Academy of Sciences, managed to extract mitochondrial DNA from dental calculus. Another team carried out an independent analysis of ancient proteins obtained from the skull's bone.
The Harbin skull, estimated to be at least 146,000 years old, is almost perfectly preserved. When it was described in 2021, researchers noted its large size, massive brow ridges and heavy upper jaw. At the same time, it was proposed that the find be assigned to a new species, Homo longi, meaning "dragon man." Other scientists immediately suspected a link to the Denisovans, but anatomical comparisons yielded contradictory results.
The Denisovans were identified as a distinct branch of ancient humans in 2010, through genetic analysis, yet until now the evidence for their existence has been largely fragmentary. The Harbin find has for the first time made it possible to connect genetic data with a nearly complete skull.
Now we have a point on the map that lets us say: "This is what Denisovans looked like."
— Karina Schlebusch, evolutionary anthropologist at Uppsala University
Initial attempts to extract DNA from the skull's bone tissue were unsuccessful. The team led by Qiaomei Fu then turned to dental calculus, a mineralized plaque that can preserve biological material far longer. From a sample weighing just 0.3 milligrams, the scientists succeeded in obtaining ancient mitochondrial DNA. This genetic material, inherited along the maternal line, matched the DNA of the Denisovans known from finds in Siberia.
The second study provided independent confirmation. Analysis of proteins extracted from the skull's temporal bone also showed similarity to Denisovans with statistical confidence of up to 100%. "Taken together, the two studies make it abundantly clear that this is a Denisovan," said palaeoanthropologist Bence Viola of the University of Toronto, who did not take part in the work.
The Harbin skull will now serve as a benchmark for comparison with other fossil remains from Asia. This should help clarify the affiliation of other finds and better our understanding of how widely the Denisovans were distributed, given that traces of them have already been found in Siberia, on the Tibetan Plateau and in Taiwan. The question of the formal classification of the Denisovans and the assignment of a species name, however, remains open.
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