A tooth unearthed in a remote cave in Laos is helping to uncover an unknown chapter in the history of human evolution.
Researchers believe the tooth belonged to a young woman who lived at least 130,000 years ago and likely belonged to the Denisova people an enigmatic group of early hominids first identified in 2010.
The lower molar is the first fossil evidence placing the Denisovans in Southeast Asia and could help solve a mystery that has long plagued experts in human evolution.
The only concrete fossils of Denisova people were found in North Asia in the cave of the same name called Denisova in the Altai Mountains of Russia in the Siberian region. However, genetic evidence has linked early hominids to locations much further south — where the Philippines, Papua New Guinea, and Australia exist today.
“This proves that Denisova people probably also existed in South Asia. And this is consistent with the findings of geneticists who claim that the ancestors of modern humans and Denisovans may have interbred in Southeast Asia. Clément Zanolli, researcher in paleoanthropology at the CNRS, the French National Center for Scientific Research, and at the University of Bordeaux.
Archaeologists discovered the tooth at a site called Cobra Cave, 260 kilometers north of Laos’ capital Vientiane, where excavations began in 2018. The study, published Tuesday in the journal Nature Communications, found the molar to be between 131,000 and 164,000 years old based on analysis of the cave’s sediments, the lifespans of three animal bones found in the same layer and the age of the rock, covering the fossil.
The tooth was unearthed in a cave in Laos and belonged to a woman who lived at least 131,000 years ago.
“Teeth are like the black box of an individual. They preserve a lot of information about its life and biology. They have always been used by paleoanthropologists to describe or distinguish between species. Therefore, paleoanthropologists (teeth) are very useful fossils for us “said Zanolli.
Comparison with early hominid teeth
The researchers compared the tooth’s protrusions and cavities to other fossilized teeth of early hominids and found that they did not resemble the teeth of Homo sapiens or Homo erectus the first early hominid to walk in an upright posture and whose remains have been found across Asia . Findings from the cave revealed that it most closely resembled a tooth belonging to a Denisovan Group jaw found on the Tibetan Plateau in Xiahe County, Gansu Province, China. The authors noted that it is possible, although less likely, that it could belong to a Neanderthal.
“Think of (the tooth) as walking through a valley between mountains. And the organization of those mountains and valleys is very speciesspecific,” Zanolli explained.
Analysis of some proteins in the enamel suggested that it must have belonged to a woman.
Denisovan DNA still exists in some people today, because after our Homo Sapiens ancestors interbred with Denisovan people, the two groups became entangled with each other and gave birth to different lives something geneticists call “genetic mixing.” This means that by analyzing current genetic data, we can learn more about the history of human evolution.
This “genetic mixing” happened over 50,000 years ago when the ancestors of modern humans left Africa and likely interbred with Neanderthals and Denisovans. But pinpointing exactly where this happened has proved difficult particularly in the case of the Denisovans.
Any piece of information that adds to the sparse body of hominin fossils from Asia is exciting news, said Katerina Douka, assistant professor of archaeological sciences at the University of Vienna’s Institute for Evolutionary Anthropology, who was not involved with the research.
Douka said he would have liked to have analyzed evidence “in greater number and depth” that would ensure the tooth belonged beyond a reasonable doubt to the Denisovan group.
“There is a chain of assumptions that the authors accept to confirm that this is a Denisovan fossil,” he said.
“The truth is that we have no way of knowing whether this single, poorly preserved molar actually belonged to a Denisovan, a hybrid group, or even an unknown hominin group. It could very well be a Denisovan and I would actually love it in a Denisovan how extraordinary would that be? But we need more reliable evidence,” he said.
In order to consider the tooth found in Laos as belonging to a Denisova hominin, the researchers in this study used a comparison to the Xiahe jaw as a strong reference, Douka said. Although many believed that the pine was Denisova, this issue had not yet been resolved. No DNA was recovered from the fossilized jaw, only “thin” protein evidence, he added.
“Anyone conducting studies of this group of hominins, where many important questions remain unanswered, would like to add striking new data. The difficulty is reliably identifying fossils like a Denisovan,” she added. “However, this lack of solid biomolecular data greatly reduces the impact of this new discovery and reminds us how difficult it is to work in the tropics.”
The study authors revealed that they planned to extract ancient DNA from the tooth, which would give them a more definitive answer if possible, but the warm climate makes the possibility of conducting the experiment an unlikely possibility. The research team also plans to resume excavation at the site after a pandemicrelated hiatus in hopes of making more discoveries of early hominids that may have lived in the region.
“In this type of environment, DNA doesn’t preserve itself well at all, but we’ll do our best,” said study author Fabrice Demeter, an assistant professor at the Lundbeck Foundation’s GeoGenetics Center in Denmark.