Molar reveals mysterious human species Denisovans could adapt to extreme climate

The paleoanthropologist Fabrice Demeter could not believe his own eyes. The tooth his team had found in a cave in northern Laos in 2018 was a human tooth. He could tell right away.

“It was just before lunch. My colleagues had taken the first sediment sample and in this piece of breccia, among fragments of animal teeth, we found the tooth,” says Assistant Professor Fabrice Demeter of GeoGenetics at the Globe Institute.

The tooth was short, typical of humans, but the surface was heavily wrinkled. Therefore, Fabrice Demeter and his colleagues had no doubt that it was a human molar, but a species different from ours.

Fabrice Demeter and his colleagues examining a sediment sample. Photo: Fabrice Demeter.

“Using paleoproteomic analysis in combination with geometric morphometric studies, we were able to determine that this is a molar from a Denisovan girl who lived approximately 164-130,000 years ago in the Middle Pleistocene. Because the molar had not yet erupted, therefore not worn out, we could also assess with great certainty the age of the girl at four-six years old, ”explains Fabrice Demeter, who, with his team, spent three years analyzing the molar.

The first sign of the Denisovans was discovered in 2010, when researchers found the tip of a finger bone in the Altai Mountains in Siberia. The bone is about 40,000 years old. Since then, other researchers have shown that the right half of a lower jaw found in a cave in the Himalayas and dating from around 160,000 years ago also came from the Denisovans.

Extreme cold in the mountains – heat and humidity in the tropics

Professor Eske Willerslev is head of the Willerslev Group at the University of Copenhagen, where this new study was conducted in collaboration with an international team comprising researchers from France, Australia, the United States and the Laos. Eske Willerslev believes the study fundamentally changes our knowledge of Denisovans:

“We have almost no material from the Denisovans, and what has been found in the past is from Siberia and the Himalayas, which are very cold, high-altitude regions. This is the first time that we find something that far south.The discovery of the molar thus changes our understanding of the geographic distribution of the Denisovans.

Human race

During the late Middle to Late Pleistocene, five human species were contemporaneous: Homo erectus, Denisovans/Neanderthals, Homo floresiensis, Homo luzonensis, and Homo sapiens. There are no extant species belonging to the first four groups, while modern humans, Homo sapiens, are the only extant species of the genus Homo.

Denisovans and Neanderthals had a common ancestor. They are both subgroups of the genus Homo.

Research has traditionally suggested that only modern humans were able to adapt to different climates.

“We used to see prehistoric people as very bad at spreading. We just didn’t think they could,” says Eske Willerslev and continues:

“But in recent years we’ve seen that Neanderthals were perhaps more widespread than previously thought. Now comes this study. It’s more extreme than anything. Because as Neanderthals moved from climates cold to temperate, this study shows that the Denisovans knew how to adapt to extremes, from the Himalayas, where it is cold, to the tropics.

Denisovans are closely related to Neanderthals

Fabrice Demeter and his colleagues have been exploring the northern region of Laos for 20 years. However, it is a hot and humid region, which makes it difficult to find well-preserved fossils.

But in good storage conditions, bones and teeth can last for thousands of years in the region.

“Rainwater carried bones and teeth, mud and soil into caves, where they were compressed. In this way, the bones can survive in the tropical climate. And it is precisely in such a cave wall that we found the Denisovan girl’s molar,” says Fabrice Demeter.

The Cobra cave in northern Laos. Photo: Fabrice Demeter.

The Indochinese peninsula has been on the map of anthropological research since the 1900s. At that time, the focus was on finding the missing link between apes and humans. In Indonesia and China, researchers had already found the missing link in the form of Homo erectus.

Due to the wars in Indochina from 1946 to 1991, the researchers had to suspend the excavations. Nevertheless, from the beginning of the 1990s, the field regained interest, and during the last 40 years, research has seen great progress thanks to collaborations with local scientists.

In 2012, Fabrice Demeter and his colleagues found the remains of several Homo sapiens individuals in a cave called Tam Pà Ling, which means monkey cave, dating back around 60-70,000 years.

Using a toothbrush, Fabrice Demeter cleans the molar. Photo: Fabrice Demeter.

And just 50 meters from Tam Pà Ling, in Cobra Cave, Fabrice and his colleagues found the Denisovan molar in 2018.

From DNA analyzes of the molar, finger bone and jaw bone found earlier, the researchers found that the Denisovans were part of the genus Homo and were closely related to Neanderthals.

“It’s kind of the Asian version of Neanderthals. In fact, modern Aborigines, Filipino Negritos, and Melanesians share 5% of their DNA with Denisovans, which is a high number. In comparison, the Danes share less than 0.001% of their DNA with the Denisovans and 2% with the Neanderthals”, specifies Fabrice Demeter and adds:

“Some of these modern populations living in the Himalayas can adapt better to high altitudes, and this may be the explanation. It may be because they contain a greater amount of DNA from Denisovan.

Read the full study, “A Middle Pleistocene Denisovan molar from the Annamite Range of northern Laos,” in Nature Communications.

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