The discovery of an ancient molar tooth – a tooth that likely belonged to a young girl who lived 164,000 years ago in a cave in what is now Laos – is new evidence of a mysterious human lineage. named Denisovans, previously known only from caves in Siberia. and China, also live in Southeast Asia, a new study shows.
“This shows that the Denisovans lived in a wide variety of environments and latitudes and were able to adapt to extreme conditions, from the frigid mountains of the Altai [in Russia] and Tibet to the rainforests of Southeast Asia,” study co-author Clément Zanolli, a paleoanthropologist at the University of Bordeaux in France, told Live Science.
Zanolli added: “Genetic studies indicate that Denisovans were adapted to high altitudes and cold climates, but we now also know that they lived in warmer, wetter climates and at high altitudes. short.
Although modern man, Homo sapiensare currently the only living members of the genus Homo – human family tree – the lineages other people have lived on The earth. The closest extinct relatives of modern humans include the Neanderthals of Europe and Asia and the new Denisovan lineage found in Asia and Oceania.
Related: Oldest known fossil of mysterious human lineage discovered in cave in Siberia
Previous research It is estimated that the ancestors of modern humans diverged about 700,000 years ago from the birth lineage of Neanderthals and Denisovans, and that the ancestors of Neanderthals and Denisovans diverged about roughly 700,000 years ago. 400,000 years ago. However, fossil genetic analysis of these extinct lineages shows that they are still close enough to interbreed with modern humans.
Much remains a mystery about the Denisovans. So far, researchers have discovered only five fossils with a solid connection to them – three upper molars, a finger bone and a finger bone. jowl – this greatly limits what researchers know about them in general. Scientists have discovered a skull in China dubbed “dragon man“claims it to be a newly found species, Homo longibut many other researchers suspect it could be a Denisovan skull.
Exactly where the Denisovans lived is debated. The fossils unearthed so far all come from the Asian continent, but before that genetic evidence suggests that people in Oceania and the islands of Southeast Asia possess Denisovan heritage.
Now, the new tooth may be the first fossil evidence of Denisovans in Southeast Asia. “Any additional fossils described as Denisovan are relevant for a better understanding of their biology and evolution“, study co-author Fabrice Demeter, a paleoanthropologist at the University of Copenhagen, told Live Science.
Scientists discovered the tooth in 2018 at a site known as the Cobra Cave in Laos’ Annamite Mountains, whose entrance lies about 110 feet (34 meters) above the ground. The limestone cave, technically known as Tam Ngu Hao 2, was found due to its proximity to another site where previous research had unearthed ancient fossils of modern humans. (The cobra’s cave also includes fossils of animals, such as rhinotapir and sambar deer.)
“Even if recent genetic studies suggest that Denisovans and modern humans met in southern Asia during the late Pleistocene [2.6 million to 11,700 years ago]Study co-author Laura Shackelford, a paleontologist at the University of Illinois Urbana-Champaign, told Live Science.
That tooth is an undeveloped molar on the left side of the lower jaw. This suggests it belonged to a child about 3.5 to 8.5 years old. Analyze the dirt and rock around the tooth using techniques such as luminescence dating, analyzing how long the mineral grains were last exposed to sunlight to estimate their age, and determine their age. radiometric dating, which measures the age of things based on a given time period. chemical element for radioactive decay, indicating that this molar is between 131,000 and 164,000 years old.
By analyzing the proteins in tooth enamel, the team confirmed that it came from the genus Homo. Absence of proteins associated with a Y chromosome suggests that the tooth came from a woman. (Researchers did not analyze ancient fossils DNA because this genetic material is rarely well preserved in the type of sediments found in caves and in the tropical conditions that exist in Laos.)
Related: Neanderthals and Denisovans lived (and mate) in this Siberian cave
When the scientists compared these molars to the teeth of other hominins – the group that includes humans, our ancestors and our closest evolutionary relatives like Australopithecus – they found its internal and external 3D structure resembles that of Neanderthals, but slightly outside their range of known variations. Moreover, teeth are also different from those of modern humans and Homo erectus, The first humans knew how to use relatively sophisticated stone tools. Although scientists cannot rule out it as belonging to a Neanderthal, they suggest that it bears a close physical resemblance to the Denisovan specimen from China suggesting the molars were likely Denisovan.
Shara Bailey, a paleontologist at New York University who was not involved in the study, told Live Science: “The tooth indicates that Denisovans were indeed in Southeast Asia, which has important implications for with understanding their scope. “We know their DNA goes there – it was present in recent Southeast Asian groups – but this suggests that the population was also present in the region.”
Even if this new fossil is not Denisovan, any new hominid fossil from an area where few ancient human fossils have been excavated to date, such as Laos, “is very important, especially especially if it’s notsapiens Chris Stringer, a paleoanthropologist at the Natural History Museum in London who was not involved in the study, told Live Science.
To that, Bailey said: “I think this is a good study and a solid conclusion. “I agree with their assessment of the tooth.”
The new findings may shed light on the extent to which different human lines may have coexisted. “Neanderthals lived in Europe and western Asia at the same time as Denisovans made up a large part of East Asia, along with other human groups such as Homo erectus, Homo floresiensis, Homo luzonensis and modern man,” said Shackelford. However, it remains unclear where, when and where all of these extinct groups might have met. “
These findings suggest that other Asian fossils need to be reanalyzed using modern techniques. “I believe we will see more Denisovans there,” Bailey said. “I know in particular about one tooth that I saw that was probably Denisovan.”
When it comes to future research, “I’m curious about how the tooth entered the cave and whether there was any human activity in the cave,” said Bence Viola, a paleontologist at the University of Toronto, who are not involved in this. told Live Science. “The excavations currently taking place will answer that.”
The scientists detailed their findings online May 17 in the journal Nature Nature Communications.
Originally published on Live Science.
https://www.livescience.com/possible-denisovan-tooth-found-laos Ancient tooth of mysterious Denisovan girl possibly found