When a team of researchers headed into the mountains of northern Laos, an area known for harboring fossilized human remains, they made a startling discovery—a tooth buried within hard sediments in a small cave.
They assessed that it likely belonged to a child from a group of extinct humans known as Denisovans, with the discovery offering an important piece of the puzzle in learning about the ancient group of which little is known.
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A report about the discovery, published on Tuesday in the peer-reviewed scientific journal Nature Communications, said the experts placed the tooth at around 164,000 to 131,000 years old, with it belonging to a girl between 3.5 to 8.5 years old. The adult tooth, which lacked signs of usage, likely had not yet emerged from the gum when she died.
The findings from the cave of Tam Ngu Hao 2, also known as Cobra Cave, were made by an international team of researchers from Laos, Europe, the U.S. and Australia. They had chanced upon the human tooth while exploring the area in northern Laos in 2019, Kira Westaway, a geochronologist at Macquarie University in Australia and a co-author of the study, told VICE World News.
“We always explore every cave on the off-chance it contains something significant,” she said. “The team conducted some digging around to check for fossils when the human tooth was spotted.”
Among other fossils they found were teeth from giant herbivores like ancient elephants and rhinos, all of which Westaway believes were originally located in the surrounding landscape, rather than in the secluded cave.
“Due to the difficulty in accessing the site, it wasn’t used [by ancient humans] for occupation so we didn’t find any stone tools,” said Westaway. “The teeth were likely washed into the cave during a flooding event that deposited the sediments and fossils.”
Denisovans, a group of ancient humans believed to have gone extinct about 20,000 years ago, are cousins of Neanderthals and Homo sapiens, connected through a common ancestor that roamed Africa 700,000 to 500,000 years ago. Neanderthals, who went extinct about 40,000 years ago, branched off and left for Europe and the Middle East. Meanwhile, another group that moved across Asia became Denisovans. Those who remained in Africa evolved into Homo sapiens, or modern humans, roughly 300,000 years ago.
As Homo sapiens fanned out across the rest of the world, they interbred with Denisovans and Neanderthals in the process. Today, some indigenous populations in and around Papua New Guinea, Australia, and the Philippines share up to 5 percent of their DNA with Denisovans.
Among modern humans, Denisovan DNA is believed to offer those with it a genetic boost. Researchers have found that Sherpas and other Tibetans possess a “superathlete” gene inherited from Denisovans, which allows them to use oxygen more efficiently at high altitudes.
While it is known Denisovans inhabited central to eastern Asia, it’s also believed that they once roamed Southeast Asia—a theory that will be proven if the newfound molar is confirmed to be Denisovan.
“We have essentially found the ‘smoking gun’—this Denisovan tooth shows they were once present this far south in the karst landscapes of Laos,” Mike Morley, of the Microarchaeology Laboratory at Flinders University, one of the co-authors, said in a press release provided to VICE World News.
The Cobra Cave is only the third site in the world where Denisovan fossils have been found. In 2010, the first fossil, part of a pinky finger bone, was found within the Altai Mountains of Siberia, in the Denisova Cave—where the extinct human group got its name.
The tooth in Laos appears to match the ones from a Denisovan jawbone found in a cave in Tibet, another rare finding that was detailed in a study published in 2019.
Denisovan molars are known to have unusual cusps that differ from modern human teeth, but for the most part, Denisovan fossils are so rare that little is known about their physical characteristics. Much of existing knowledge about this enigmatic group comes from their DNA.
Westaway says that the recent tooth finding provides a glimpse into Denisovans’ adaptability, being the first evidence of them existing in warmer climates.
“The timing is also surprising—these suspected Denisovans were living in the balmy caves of northern Laos at the same time as they were surviving in the frigid caves of Russia and living up high on the Tibetan Plateau [around] 160,000 thousand years ago,” said Westaway.
“We often attribute the ability to adapt to diverse environments as a modern human trait, and yet it looks like the Denisovans were displaying similar adaptive skills in this region but 100,000 years earlier than modern humans.”
“This certainly changes our perception of this hominin group and helps us to begin to understand the nature of these mysterious ancient humans.”
