A baby tooth demonstrates the presence of Denisova’s husband in Laos

A baby tooth at least 130,000 years old, discovered in a cave in Laos, testifies to the presence of Denisova’s men in the tropical climate of Southeast Asia, revealing part of the veil of mystery about this extinct species, according to a study published Tuesday in journal Nature communication.

Very little is known about Denisovans, an archaic human cousin of the Neanderthals, who was first identified in 2010 in a cave in Siberia. From a simple piece of phalanx, paleontologists were able to sequence a complete genome. They then found in 2019 a mandible with large teeth on the Tibetan plateau, proving that the species had also lived in this part of China.

In Siberia, in the footsteps of Denisova’s man, an extinct human species

Apart from these rare fossils, Denisova’s husband had left no trace of his passage … Apart from the genes since before his disappearance, this so-called archaic species interfered with Homo sapiensand bequeaths some of its DNA to current populations in Southeast Asia and Oceania: Negritos from the Philippines, Papuans from New Guinea, and Aborigines in Australia have a large share of the Denisovan genome – up to 5%.

Geneticists have deduced that “the modern ancestors of these peoples had ‘hybridized’ with Denisovans in Southeast Asia“Paleoanthropologist Clément Zanoli, co-author of the study, explains to AFP. But there was a lack of” physical evidence “of their presence in this part of the Asian continent, far from the cold mountains of Siberia or Tibet, adds this.

Until a team of scientists set out to excavate the Cobra Cave in northeastern Laos. The cavity, which lies on a massive, was discovered in 2018 by speleologists near the site of Tam Pa Ling, known for having already supplied the remains of very old people. The sediments preserved in the cave walls contained bone fragments of animals as well as a cheek tooth.

Position of Cobra Cave (left) and sedimentary breccia containing the fossils inside the cave (right). © C. Zanolli

The tooth immediately presented a morphology “typically human“, says Clément Zanolli. It must have belonged to a child of 3 to 8 years because it was still growing in the jaw, the study clarifies. But from what time, what species? The tooth was too old for carbon dating 14, and its poorly preserved DNA on due to the hot and humid climate, emphasizes paleoanthropologist Fabrice Demeter, co-author.

The researchers therefore circumvented the obstacle by dating the sediments that contained the tooth and the remains of the fauna, then the top layer, to achieve a range of 160,000 to 130,000 years.

little girl cheek tooth

They then studied the inside of the tooth – temporarily exported to Denmark – using various methods such as X-ray microtomography and paleoproteomics (protein analysis). “The proteins enabled us to identify the sex, the woman, and confirm its membership of the genus Homo“, Says Fabrice Demeter, researcher at the University of Copenhagen affiliated with the Statens Naturhistoriske Museum in Paris.

Virtual rendering of Denisovan TNH2-1 molar from Cobra Cave showing semi-transparent enamel (blue) and underlying dentin (yellow). © C. Zanolli

And surprisingly, the inner structure of the tooth turned out to be close to the cheek teeth on Denisova’s sample from Tibet. “I was really expecting a Homo erectus!“, remembers the paleoanthropologist. But no doubt the molar was easy to distinguish from this ancient species, as well as other extinct groups endemic to the Philippines and Indonesia, Homo floresiensis and Homo luzonensis. And of course the modern man.

Scientists discover unknown 50,000-year-old human species in the Philippines

The only problem: it had common characteristics with the Neanderthals, genetically close to the Denisovans – the two species would have diverged about 350,000 years ago. “But we leaned against Denisova because we never found the trail of the passage of Neanderthals also in the east“, Specifies Clément Zanoli.

The Denisovans therefore occupied this part of Asia, a sign of adaptation to a wide range of environments, from cold altitudes to tropical climates, the study concludes. en “versatility“which their Neanderthal cousins ​​did not seem to possess, any more”specialized“about the cold regions of the West, details Fabrice Demeter.

It was in the tropics that the later Denisovans could have met and hybridized with local modern human groups from the Pleistocene era, who passed on their genetic heritage to today’s Southeast Asian peoples.

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