Tooth found in Laotian cave may be from Denisovan girl

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The discovery of a single, worn molar from a hominin found embedded in the ceiling of a cave in northern Laos is attracting a lot of attention.

The tooth is a lower molar and was discovered in the Annamite Mountains at Tam Ngu Hao 2 (Cobra Cave) in Huà Pan province of Laos, some 160 mi (roughly 260km) north of the capital, Vientiane, and has been dated from between 131,000 and 164,000 years ago, based on analysis of cave sediment, dating of some animal bones from the same layer, and the age of rock overlying the fossil. The fact that the tooth’s roots were not fully developed indicates it was from a child and lacked certain peptides in the enamel associated with the Y chromosome, suggesting the owner had been a female.

What is causing the interest is that it appears to have come from a Denisovan, an extinct species of archaic human who existed during the Early and Middle Paleolithic Age first identified just a little over a decade ago after the discovery of the tip of a finger bone found in a cave in the Altai Mountains in south-central Siberia. Later, several teeth were also discovered at the same site. Around this time, a jawbone was found in Baishiya Karst Cave on the Tibetan plateau in Xiahe county, in Gansu province, China that is very likely Denisovan in origin, although there is a slim chance it could be from a Neanderthal.

If the identification of the Tam Ngu Hao 2 tooth is indeed Denisovan, that moves their fossil range thousands of miles south. This really comes as no surprise given how a couple of recent genetic studies have shown that millions of people from Asia, Oceania and the Pacific Islands carry traces of Denisovan DNA, with the highest amounts (about 5%) occurring in Melanesians, Aboriginal Australians, and Filipino Negritos.

The researchers said that their identification was based on three different factors.

First, they compared the ridges and dips on the molar with other fossilized teeth belonging to archaic humans and concluded that it didn’t resemble teeth belonging to Homo sapiens or Homo erectus, but rather, morphologically speaking, much closer resembled a tooth found in the jawbone from Tibet.

Much of the analysis seems based on the similarity to the tooth in the Tibetan jaw, but it should not be forgotten that there remains some uncertainty over its identification. Moreover, the worn condition of the Laos tooth makes comparison less certain than anyone would like.

Still, if it isn't from a Denisovan, then that means almost certainly from a Neanderthal then (greatly expanding their known range) or a new previously unknown species. Either would be a huge discovery as well.

Anyway, I mentioned three factors that went into determining that it was from a Denisovan. That is that a paleoproteomic analysis shows it to be Denisovan and Denisovan DNA was identified in the cave sediment.

The team plans on trying to extract ancient DNA from the tooth, which, if possible, will provide a more definitive answer, but the warm and humid climate of where it was found means that is a long shot.

Source: Ancient tooth suggests Denisovans ventured far beyond Siberia

Molar found in Laos could be the first fossil evidence that the hominin species was far-ranging and able to adapt to different climates.

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The fossilized molar, seen here from several angles, is thought to have belonged
to a young Denisovan girl that died between 164,000 and 131,000 years ago.

A fossilized tooth unearthed in a cave in northern Laos might have belonged to a young Denisovan girl that died between 164,000 and 131,000 years ago. If confirmed, it would be the first fossil evidence that Denisovans — an extinct hominin species that co-existed with Neanderthals and modern humans — lived in southeast Asia.

The molar, described in Nature Communications on 17 May¹, is only the second Denisovan fossil to be found outside Siberia. Its presence in Laos supports the idea that the species had a much broader geographic range than the fossil record previously indicated.

“We’ve always assumed that Denisovans were in this part of the world, but we’ve never had the physical evidence,” says study co-author Laura Shackelford, a palaeoanthropologist at the University of Illinois Urbana-Champaign. “This is one little piece of evidence that they were really there.”

Expanded range

Denisovans were first identified in 2010, when scientists sequenced DNA from a fingertip bone found in Denisova cave in Siberia, and showed that it belonged to a previously unknown species of ancient human². Subsequent genetic studies^3,4 have revealed that millions of people from Asia, Oceania and the Pacific Islands carry traces of Denisovan DNA.

This suggests that the species ranged far beyond Siberia — but the fossil evidence has been sparse. The entire fossil record for Denisovans so far boils down to a handful of teeth, bone shards and a jawbone found in Tibet. Aside from the latter, every specimen (including a piece of bone that belonged to a half-Denisovan girl whose mother was a Neanderthal) has come from Denisova cave.

That’s partially because fossils have a better chance of surviving in cold, dry conditions than in warm, humid ones. But in 2018, Shackelford and her colleagues were looking for potential dig sites in northern Laos when they came across a cave “just filled with teeth”. These belonged to a mixture of species, including giant tapirs, deer, pigs and ancient relatives of modern elephants. The collection was probably amassed by porcupines collecting bones to sharpen their teeth and extract nutrients, says Shackelford. Among the first batch of fossils to come out of the cave was a small, underdeveloped hominin tooth.

Dating of the cave’s rock and animal teeth revealed that the tooth pre-dated the arrival of modern humans in the area. “It was just a huge surprise,” says Shackelford, who says the team wasn’t expecting to find ancient-human remains. At first, the researchers thought the tooth might belong to Homo erectus — an ancient-human species that lived in Asia between around 2 million and 100,000 years ago. But the molar is “too complex” to belong to H. erectus, the researchers say, and although it shares some characteristics with Neanderthal teeth, it is also “large, and kind of weird”, says Bence Viola, a palaeoanthropologist at the University of Toronto in Canada.

The molar has the greatest resemblance to teeth found in the Denisovan jawbone from Tibet. “Denisovans have absolutely gigantic teeth,” Viola says. “So it seems like a good assumption that this is likely a Denisovan.”

The tooth’s roots are not fully developed, so it probably belonged to a child, the researchers say. They also found that it lacked certain peptides in its enamel that are associated with the Y chromosome — a possible indication that its owner was female.

Right place, right time

Reconstructing the identity of a person whose bones have been degraded by thousands of years of tropical conditions is challenging, says Katerina Douka, an archaeological scientist at the University of Vienna. Without more fossils or DNA analysis, “the reality is that we cannot know whether this single and badly preserved molar belonged to a Denisovan”, she says.

But Viola says that the molar is in the “right place and right time” to belong to a Denisovan. If this were confirmed, it would reveal that the species was able to adapt to different environmental conditions. At the time the tooth’s owner died, more than 131,000 years ago, the area would have been lightly wooded and temperate — completely different from the frigid temperatures faced by Denisovans in Siberia and Tibet. The ability to live in a wide range of climates would set the Denisovans apart from Neanderthals — whose bodies were adapted for colder places — and make them more similar to our own species.

Even with the uncertainty, the discovery is likely to encourage other researchers to look for ancient-human fossils in southeast Asia, says Viola.

“When we started looking in Laos, everyone thought we were crazy,” says Shackelford. “But if we can find things like this tooth — which we weren’t even anticipating — then there are probably more hominin fossils to be found.”


Source

© Copyright Original Source

The full paper, A Middle Pleistocene Denisovan molar from the Annamite Chain of northern Laos can be accessed by clicking the hyperlink, and the abstract from it is available below:

The Pleistocene presence of the genus Homo in continental Southeast Asia is primarily evidenced by a sparse stone tool record and rare human remains. Here we report a Middle Pleistocene hominin specimen from Laos, with the discovery of a molar from the Tam Ngu Hao 2 (Cobra Cave) limestone cave in the Annamite Mountains. The age of the fossil-bearing breccia ranges between 164–131 kyr, based on the Bayesian modelling of luminescence dating of the sedimentary matrix from which it was recovered, U-series dating of an overlying flowstone, and U-series–ESR dating of associated faunal teeth. Analyses of the internal structure of the molar in tandem with palaeoproteomic analyses of the enamel indicate that the tooth derives from a young, likely female, Homo individual. The close morphological affinities with the Xiahe specimen from China indicate that they belong to the same taxon and that Tam Ngu Hao 2 most likely represents a Denisovan.