A baby tooth at least 130,000 years old, found in a cave in Laos, could help scientists uncover more information about an early human cousin, according to a new study.
Researchers believe the discovery proves that the Denisovans – an extinct branch of humanity – lived in the warm tropics of Southeast Asia.
Very little is known about the Denisovans, cousins of the Neanderthals.
Quick guide
Who were the Denisovites?
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Denis are a sister species Homo sapiens and Neanderthals, but much less is known about them, including what they would look like.
Their existence was revealed by DNA analysis of a finger bone found in the Denis Cave in Siberia. This showed that the fossils belonged to a new species that, along with the Neanderthals, separated from our own line about 700,000 years ago.
Soon after this division, the Denisovans and Neanderthals set out on their own paths, though not definitively. There is clear evidence of crossbreeding between the two extinct species, as well as with modern humans.
About 3% to 5% of the DNA of Melanesians and Australian Aborigines and about 6% of Papuans appear to be from Denisovans. These genetic comparisons suggest that Denisovites must have once been widespread.
Since Siberian fossils are just a few pieces of bone and teeth, a crucial part of the puzzle is trying to match DNA evidence with more complete fossils found elsewhere, including in China, to get a better idea of what our ancient cousins looked and how they lived.
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Scientists first discovered them while working in a Siberian cave in 2010 and found a finger bone from a girl belonging to an unidentified group of people.
Using only finger and wisdom teeth found in Denis Cave, they extracted the entire genome of the group.
Researchers then discovered a jawbone in 2019 on the Tibetan Plateau, proving that some of the species also lived in China.
Apart from these rare fossils, the Denisovans left a small mark before they disappeared – except in the genes of human DNA today.
By crossing with Homo sapiens, Denisovian remains can be found in current populations in Southeast Asia and Oceania.
Aboriginal Australians and people in Papua New Guinea have up to five percent of the DNA of the ancient species.
The researchers concluded that “the modern ancestors of these populations were ‘mixed’ with Denisovans in Southeast Asia,” said Clement Zanoli, a paleoanthropologist and co-author of the study, published Tuesday in Nature Communications.
But there is no “physical evidence” of their presence in this part of the Asian continent, far from the icy mountains of Siberia or Tibet, a researcher from the French National Research Center told AFP.
This was until a group of scientists began searching the Cobra Cave in northeastern Laos.
Cave experts discovered the area in the mountains in 2018 next to the cave Tam Pa Ling, where the remains of ancient people have already been found.
It immediately turned out that the tooth had a “typically human” shape, Zanoli explained.
According to the study, based on ancient proteins, the tooth belongs to a child, probably a woman, aged between 3.5 and 8.5 years.
But the tooth is too old for carbon dating, and DNA is poorly preserved due to heat and humidity, said paleoanthropologist and co-author Fabrice Demeter.
After analyzing the shape of the tooth, scientists believe that it is most likely a Denisovite who lived 164,000 to 131,000 years ago.
They then examined the inside of the tooth using various methods, including protein analysis and 3D X-ray reconstruction.
The internal structure of the tooth is similar to that of the molars found in the Tibetan specimen Denisova. It was clearly distinguishable from modern humans and other ancient species that lived in Indonesia and the Philippines.
“Protein has allowed us to identify gender – female – and confirm its link to the Homo species,” said Demeter, a researcher at the University of Copenhagen in Denmark, where the tooth is temporarily based.
The structure of the tooth has common characteristics with Neanderthals, which are genetically similar to Denisovans. The two species are thought to have separated about 350,000 years ago.
But Zanoli explained that researchers have concluded that this is a specimen from Denisova, as no traces of Neanderthals have been found in the east so far.
For Demeter, the finding shows that the Denisovans occupied this part of Asia and adapted to a wide range of environments, from cold altitudes to tropical climates, while their Neanderthal cousins seemed more “specialized” in the cold western regions.
Therefore, the last Denisovites could meet and interbreed with modern humans, who passed on their genetic heritage to modern populations of Southeast Asia in the Pleistocene.
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