Archaeologists discover key fossil tooth in human evolution

Archaeologists discover key fossil tooth in human evolution

(CNN) — A tooth unearthed from a remote cave in Laos helps chart an unknown chapter in human history.Researchers believe the tooth belonged to a young woman who lived at least 130,000 years ago and likely belonged to the Denisovans, an enigmatic group of early humans first identified in 2010.

The lower molar is the earliest fossil evidence placing the Denisovans in Southeast Asia and may help solve a puzzle that has long troubled human evolution experts.

The only definitive Denisovan fossils have been found in North Asia, in the Denisovan Cave of the same name in the Altai Mountains of Siberia, Russia. The genetic evidencehowever, more closely connects archaic humans to places much further south in what is now the Philippines, Papua New Guinea, and Australia.

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

Archaeologists discovered the tooth at a location known as Cobra Cave, 260 kilometers (160 miles) north of Laos’ capital, Vientiane, where they started digging in 2018.

The study, which was published in the journal Nature Communications Tuesday, he estimated the molar to be between 131,000 and 164,000 years old, based on analysis of cave sediments, the dating of three animal bones found in the same layer and the age of the rock covering the fossil.

The tooth was unearthed from a cave in Laos and belonged to a woman who lived at least 131,000 years ago.

“Teeth are like an individual’s black box. They hold a lot of information about their life and their biology. Paleoanthropologists have always used them, you know, to describe species or distinguish species. So for us, paleoanthropologists (teeth) are very useful fossils,” Zanolli said.

Comparison with archaic human teeth

The researchers compared the cusps and grooves of the tooth with other fossilized teeth belonging to archaic humans and found that they did not resemble teeth belonging to Homo sapiens or Homo erectus, an archaic human who was the first to walk upright and whose remains have been found throughout Asia.

The discovery of the cave was more like a tooth found in a mandible of a Denisovan found on the Tibetan Plateau in Xiahe County, Gansu Province, China. The authors said it was possible, though less likely, that it could have belonged to a Neanderthal.

“Think of it (the tooth) as traveling through (a) valley between mountains. And the organization of those mountains and valleys is very typical of a species,” Zanolli explained.

Analysis of certain proteins in the tooth’s enamel suggested that it belonged to a woman.

Denisovan DNA lives in some humans because once our Homo sapiens ancestors encountered Denisovans, they had sex with them and gave birth to babies, what geneticists call admixture. This means we can look back on human history by analyzing current genetic data.

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

Definitely Denisova?

Any addition to Asia’s rare hominid fossil record is exciting news, says Katerina Douka, assistant professor of archaeological sciences in the Department of Evolutionary Anthropology at the University of Vienna. She did not participate in the investigation.

He says he would have liked to see “more and more evidence” that the tooth was indeed Denisovan.

“There are a number of hypotheses that the authors accept to confirm that this is a Denisovan fossil,” he adds.

“The reality is that we cannot know if this single, poorly preserved molar really belonged to a Denisovan, a hybrid, or even an unknown group of hominins. It could very well be a Denisovan, and I would love that he was a Denisovan, because wasn’t he? Would that be great? But more reliable evidence is needed.”

Considering the Lao tooth to be Denisovan, the researchers in this study relied heavily on a comparison with the Xiahe jawbone, Douka said. However, the jawbone, though many believed to be Denisovan, was not a closed case. No DNA was recovered from the fossilized jawbone, the only evidence of a “thin” protein, he added.

“Anyone working on this hominin group, where many big questions remain, wants to add new points to the map. The difficulty lies in reliably identifying any fossil as a Denisovan,” he said. “However, this lack of robust biomolecular data greatly reduces the impact of this new finding and serves as a reminder of how difficult it is to work in the tropics.”

It is difficult to extract DNA from this time

The study authors said they plan to try to extract ancient DNA from the tooth, which if possible would provide a more definitive answer, but the warm weather suggests it could be a long time.

The research team also plans to continue excavation of the site after a pandemic hiatus, in hopes of uncovering more ancient humans who lived in the area.

“In this type of environment, DNA is not well preserved, but we will do our best,” said Fabrice Demeter, co-author of the study and assistant professor at the Center for Geogenetics of the Lundbeck Foundation at the Denmark.

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