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A mysterious human skull found in the 1930s has been identified as an existing species after once being thought to be a new species all together, according to researchers.
The studies — posted in the journals Cell and Science — have identified the 146,000-year-old skull known as "dragon man" has been categorized as a Denisovan.
The researchers revealed that the Denisovans were discovered by their genomes and proteins to identify them.
However, the reason it took so long to identify was that the attempts to extract DNA from a tooth failed.
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The "dragon man" was once thought to be a new species of human, but using dental calculus, researchers have determined otherwise. (Mr. Wei Gao)
Researchers also tried extracting DNA from the Harbin cranium as well, which also failed.
When those methods failed, researchers turned to using dental calculus, which uses calcified dental plaque.
The calcified dental plaque could hold and protect DNA due to its dense crystalline structure that resists degradation in various environments.
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The position sampled for the 0.3 mg of dental calculus on the Harbin tooth, where mtDNA was captured and sequenced (Photo provided by Qiaomei Fu via the journal Cell)
Researchers used bleach on the dental plaque in order to eliminate any possible modern-day DNA.
Once extracted, researchers began to compare the genetic material discovered to previous samples.
The researchers found that the "dragon man" was not a new species but was a Denisovan and the very first intact specimen to date.
According to the researchers, Denisovans coexisted with modern-day humans and are closely related to Neanderthals.
A full-length artist's impression of what Dragon Man could have looked like. Image: Chuang Zhao (Natural History Museum/Chuang_Zhao)
The "dragon man" was discovered in mysterious circumstances when a Chinese laborer working on a bridge over the Songhua River found it.
The man kept the Harbin cranium well hidden as he was instructed to hide it from the Japanese army.
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The skull was donated shortly before his death in 2018, after which his family relocated the skull and gave it to the Geoscience Museum, Hebei GEO University professor Qiang Ji.
While there are limitations to this study, the researchers said there is still so much to learn moving forward.
It was called "dragon man" because it was found in the Heilongjiang province of China, which translates to Black Dragon River.
Fox News Digital’s Julia Musto contributed to this story.
Nick Butler is a reporter for Fox News Digital. Do you have any tips? Reach out to Nick.Butler@Fox.com.
Nick Butler is a Breaking and Trending News Writer for Fox News Digital.