Discovery of 'Dragon Man' DNA Reveals Face of Mysterious Ancient Group

After several failed attempts, researchers have managed to extract genetic material from a fossilized skull nicknamed "Dragon Man," linking it to a mysterious group of ancient humans known as the Denisovans, CNN reports. About a dozen fossilized bone fragments from Denisovans have previously been found and identified using ancient DNA. But the small size of the samples left little clue as to what this mysterious population of ancient hominins looked like, and the group has never been given an official scientific name.

Scientists generally consider skulls with characteristic bumps and ridges to be the best type of fossil for understanding the shape or appearance of an extinct hominid species.

“I really feel like we’ve solved part of the mystery surrounding this population,” said Qiaomei Fu, a professor at the Institute of Paleontology and Paleoanthropology, part of the Chinese Academy of Sciences in Beijing, and lead author of the new study. “After 15 years, we know of the first Denisovan skull.”

The Denisovans were first discovered in 2010 by a team including Fu, then a young researcher at the Max Planck Institute for Evolutionary Anthropology in Leipzig, based on ancient DNA contained in a pinky finger fossil found in Denisova Cave in the Altai Mountains of Russia, CNN reports. Additional remains discovered in the cave from which the group takes its name and elsewhere in Asia continue to fill in the still incomplete picture.

The new research, described in two papers published Wednesday, “will certainly be one of the most important papers in paleoanthropology this year” and will fuel debate in the field “for quite some time,” says Ryan MacRae, a paleoanthropologist at the Smithsonian’s National Museum of Natural History in Washington, who was not involved in the research.

The findings could help fill in gaps in our knowledge about a time when Homo sapiens weren’t the only humans on the planet, and tell scientists more about modern humans. Our species once coexisted for tens of thousands of years, interbreeding with both Denisovans and Neanderthals before they died out. Most modern humans carry the genetic legacy of these ancient encounters. Neanderthal fossils have been studied for more than a century, but little is known about our mysterious Denisovan relatives, and the fossil skull could reveal a lot.

In 1933, a worker in the northeastern Chinese city of Harbin discovered the skull of a dragon man, CNN reports. The man, who was building a bridge across the Songhua River when that part of the country was under Japanese occupation, took the specimen home and placed it at the bottom of a well for safekeeping.

The man never claimed his treasure, and the skull, with one tooth still embedded in its upper jaw, remained unknown to science for decades until his relatives learned of it before his death. His family donated the fossil to Hebei Geoscience University, and researchers described it for the first time in a series of studies published in 2021 that found the skull to be at least 146,000 years old.

The researchers argued that the fossil deserved a new species name given the unique nature of the skull, calling it Homo longi, after the province of Heilongjiang, or Black Dragon River, where the skull was found. At the time, some experts hypothesized that the skull might have belonged to a Denisovan, while others linked it to other hard-to-classify fossils found in China, sparking heated debate and making the molecular data from the fossil particularly valuable.

Given the age of the skull and its history, Professor Fu said she knew it would be a challenge to extract ancient DNA from the fossil to better understand where it fits in the human family tree. “There are only bones from four sites in the world that are older than 100,000 years that contain ancient DNA,” she said.

Professor Fu and her colleagues tried unsuccessfully to extract ancient DNA from six samples taken from Dragon Man's preserved tooth and the skull's os peduncle - a dense fragment at the base of the skull that is often a rich source of DNA in fossils.

The team also attempted to extract genetic material from the skull's tartar — deposits on teeth that can form a hard layer over time and trap DNA in the mouth. Through this process, the researchers were able to recover mitochondrial DNA, which is less detailed than nuclear DNA but revealed a link between the sample and the known Denisovan genome, according to a new paper published in the journal Cell.

“Mitochondrial DNA makes up only a small part of the entire genome, but it can tell us a lot. It is limited by its relatively small size compared to nuclear DNA and the fact that it is inherited only through the mother, not from both biological parents,” explains MacRae.

“So without nuclear DNA, one could speculate that this individual is a hybrid with a Denisovan mother, but I think that scenario is much less likely than this fossil being a full-fledged Denisovan,” he added.

The team also extracted protein fragments from fossilized bone samples, which also suggested that the dragon-man skull belonged to Denisovans, according to a separate paper published Wednesday in the journal Science.

Taken together, "these studies increase the likelihood that the Harbin skull belonged to a Denisovan," says Professor Fu.

The molecular data presented in the two papers are potentially very important, said anthropologist Chris Stringer, head of human origins research at London’s Natural History Museum. “I’ve been collaborating with Chinese scientists to carry out new morphological analyses of human fossils, including from Harbin,” he said. “Combined with our research, this work makes it increasingly likely that Harbin is the most complete Denisovan specimen found to date.”

However, Xijun Ni, a professor at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing who worked with Stringer on the original Dragon Man study but not the latest research, said he was cautious about the results of the two papers because some of the DNA extraction methods used were “experimental.” Professor Ni also said he found it odd that DNA was obtained from the surface of the tartar but not from inside the tooth and tartar bone, given that the tartar appeared to be more susceptible to potential contamination.

However, he added that he believed it was likely that the skull and other fossils identified as Denisovans belonged to the same human species.

The aim of using the new extraction method was to recover as much genetic material as possible, Professor Fu explains, adding that the dense crystalline structure of tartar may help prevent the loss of host DNA.

The protein signatures Fu and her team found point to “a Denisovan identity, and other indications are very unlikely,” said Frido Welker, an associate professor of biomolecular paleoanthropology at the Globe Institute at the University of Copenhagen in Denmark. Welker has extracted Denisovan proteins from other candidate fossils but was not involved in this study.

"With the Harbin skull now linked to Denisovans based on molecular data, most hominin fossils can be reliably matched to the known Denisovan specimen based on morphology," he said.

With the dragon man skull now linked to Denisovans based on molecular data, paleoanthropologists will have an easier time classifying other potential Denisovan remains from China and elsewhere. MacRae, Ni, and Stringer said they believe it is likely that Homo longi will become the official species name for Denisovans, although other names have been proposed.

The finds also reveal a little more about what Denisovans might have looked like, assuming the “dragon man” skull belonged to a typical human. According to MacRae, the ancient human had very strong brow ridges, a brain “comparable in size to Neanderthals and modern humans,” but larger teeth than both relatives. Overall, Denisovans had a massive, robust appearance.

“They are still our more mysterious relatives, just a little less mysterious than they used to be,” he added. “There’s still a lot of work to be done to figure out exactly who the Denisovans were and how they are related to us and other hominins.”