Girl’s tooth found in Laos cave could be first ancient fossil of its kind in Southeast Asia
A tooth unearthed in a remote cave in Laos helps sketch an unknown chapter in the human story.
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.
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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 Denisova fossils have been found in northern Asia named after the group – the Denisova Cave in the Siberian Altai Mountains in Russia.
However, genetic evidence has most closely linked 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,” said study author and paleoanthropology researcher at CNRS, the French National Center for Scientific Research, and the University of Bordeaux Clément Zanolli.
“And it supports the results of geneticists who say that modern humans and the Denisovans may have met in Southeast Asia.”
Archaeologists have uncovered the tooth at a site known as Cobra Cave, 260 km north of Laos’ capital, Vientiane, where excavations began in 2018.
Archaeologists have uncovered the tooth at a site known as Cobra Cave, 260 km north of Laos’ capital, Vientiane, where excavations began in 2018. Credit: Fabrice Demeter
The study, published Tuesday in Nature Communications, estimated the molar to be between 131,000 and 164,000 years old.
Their estimate was based on an analysis of 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 keep a lot of information about their life and biology. They’ve always been used by paleoanthropologists, you know, to describe species or to differentiate between species,” Zanolli said.
“So paleoanthropologists (teeth) are very useful fossils.”
Comparison with Archaic Human Teeth
The researchers compared the ridges and pits on the tooth with other fossilized teeth from archaic humans.
It did not resemble the teeth of Homo sapiens or Homo erectus – an archaic human who was the first to walk with an upright gait, the remains of which have been found throughout Asia.
The cave resembled a tooth found in a Denisovan jawbone on the Tibetan Plateau in Xiahe Province, Gansu Province, China.
The authors said it could, though less likely, belong to a Neanderthal.
“Think about (the tooth) as if you were traveling to (a) valley between mountains. And the organization of these mountains and valleys is typical of a species,” explains Zanolli.
The researchers compared the ridges and pits on the tooth with other fossilized teeth from archaic humans. Credit: Fabrice Demeter
Analysis of a protein in the tooth’s enamel 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.
We can look back into human history by analyzing current 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.
Any addition to Asia’s meager hominin fossil record is exciting news, Assistant Professor of Archaeological Sciences at the University of Vienna in the Department of Evolutionary Anthropology Katerina Douka.
She was not involved in the investigation but said she would have liked to see “more comprehensive evidence” that the tooth was definitively Denisovan.
“There is a series of assumptions the authors accept to confirm that this is a Denisovan fossil,” she said.
“We cannot know whether this single and poorly preserved molar belonged to a Denisovan, a hybrid, or even an unknown hominin group.
“It could very well be a Denisovan, and I’d love to be a Denisovan because how cool would that be? But more reliable evidence is needed.”
The study authors said they planned to extract ancient DNA from the tooth, which, if possible, would provide a more definitive answer as to whether the fossil is Denisovan. Credit: Fabrice Demeter
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. She added that no DNA had been recovered from the fossilized jawbone, only “thin” protein evidence.
“Everyone working on this group of hominids, which still has many big questions, 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 reminds us of how difficult it is to work in the tropics.”
The study authors said they plan to extract ancient DNA from the tooth, which, if possible, would provide a more definitive answer, but the warm climate means it could be a long way.
The research team also plans to continue excavating the site after a pandemic-induced hiatus in hopes of more discoveries about ancient people living there.
“In these environments, DNA doesn’t hold up well at all, but we’ll do our best,” said study co-author Lundbeck Foundation GeoGenetics Center assistant professor Fabrice Demeter.