A tooth found in a cave in Laos reveals more about the mysterious Denisovans

Researchers believe the tooth belonged to a young woman who lived at least 130,000 years ago and was likely a Denisovan — an enigmatic group of early humans first identified in 2010.

The lower molar is the first fossil evidence that Denisovans have been placed in Southeast Asia and may help unravel a puzzle that has long tormented experts in human evolution.

The only definitive Denisovan fossils have been found in Northern Asia – in the eponymous Denisova Cave in the Siberian Altai Mountains in Russia. However, genetic evidence has most closely linked the Archaic humans to places much further south – in what are now the Philippines, Papua New Guinea and Australia.

“This shows that the Denisovans were probably also present in South Asia. And it supports the results of geneticists who say that modern humans and the Denisovans may have met in Southeast Asia,” said study author Clément Zanolli, a researcher in paleoanthropology. at CNRS, the French National Center for Scientific Research and the University of Bordeaux.

Archaeologists discovered the tooth in a site known as Cobra Cave, 160 miles (260 kilometers) north of Laos’ capital, Vientiane, where excavations began in 2018. The study, published Tuesday in the journal Nature Communications, estimated the molar to be between 131,000 and 164,000 years old, based on analysis of the cave. sediment, the dating of three animal bones found in the same layer, and the age of the rock overlying the fossil.

“Teeth are like an individual’s black box. They store a lot of information about their lives and biology. They’ve always been used by paleoanthropologists, you know, to describe species or to differentiate between species. So for us paleoanthropologists (teeth) are very useful fossils,” Zanolli said.

Comparison with Archaic Human Teeth

The researchers compared the ridges and pits on the tooth with other fossilized teeth from archaic humans and found that it did not resemble teeth from Homo sapiens or Homo erectus — an archaic human who was the first to walk with an upright gait whose remains have been found in Asia. . The cave find most closely resembled a tooth found in a Denisovan jawbone found on the Tibetan plateau in Xiahe Province, Gansu Province, China. The authors said it could possibly, though less likely, belong to a Neanderthal.
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“Think about (the tooth) as if you were traveling to (a) valley between mountains. And the organization of these mountains and valleys is very typical of a species,” explains Zanolli.

analysis of some protein in the enamel of the tooth suggested it belonged to a woman.

Denisovan DNA lives on in some people today because, when our Homo sapiens ancestors met the Denisovans, they had sex with them and gave birth to babies — something geneticists call mixing. This means we can look back into human history by analyzing contemporary genetic data.

The “mixing” was thought to have happened more than 50,000 years ago, when modern humans left Africa and likely crossed paths with both Neanderthals and Denisovans. But pinpointing exactly where it happened has proven difficult, especially in the case of Denisovans.

Absolutely Denisovan?

Any addition to Asia’s meager hominin fossil record is exciting news, said Katerina Douka, an assistant professor of archaeological sciences in the department of evolutionary anthropology at the University of Vienna. She was not involved in the investigation.

She said she would have liked to see “more and comprehensive evidence” that the tooth was definitively Denisovan.

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“There is a series of assumptions the authors accept to confirm that this is a Denisovan fossil,” she said.

“The reality is that we cannot know whether this single and poorly preserved molar indeed belonged to a Denisovan, a hybrid, or even an unknown group of hominins. It could very well be a Denisovan, and I would be thrilled to have a Denisovan because how cool would that be? But more reliable evidence is needed,” she said.

When considering the Laos tooth Denisovan, the researchers in this study relied heavily on a comparison with the Xiahe jawbone, Douka said. However, the jawbone, although considered by many to be Denisovan, was not an open and closed case. No DNA had been recovered from the fossilized jawbone, only “thin” protein evidence, she added.

“Anyone working on this group of hominids, where many important questions remain, wants to add new dots to the map. The difficulty is reliably identifying fossils as those of a Denisovan,” she said. “However, this lack of robust biomolecular data significantly reduces the impact of this new find and it reminds us of how difficult it is to work in the tropics.”

The study authors said they planned to extract ancient DNA from the tooth, which, if possible, would provide a more definitive answer, but the warm climate means that could go a long way. The research team also plans to continue excavating the site after a pandemic-induced hiatus in hopes of more discoveries of ancient people who lived in the area.

“In these kinds of environments, DNA doesn’t hold up well at all, but we’ll do our best,” said co-author Fabrice Demeter, an assistant professor at the Lundbeck Foundation GeoGenetics Center in Denmark.

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