How Denisovans survived the ‘roof of the world’

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Denisovans survived on the high Tibetan Plateau for more than 100,000 years, according to a new study that deepens scientific understanding of the enigmatic ancient humans first identified in 2010.

The researchers examined thousands of animal bone fragments found in Baixia Karst Cave, 3,280 meters above sea level near the city of Xiahe in China’s Gansu province – one of three known places where extinct humans lived. Their work revealed that Denisovans could hunt, butcher, and process a variety of large and small animals, including woolly rhinoceros, blue sheep, wild yaks, marmots, and birds.

A team of archaeologists working in the cave found a rib fragment in a layer of sediment between 48,000 and 32,000 years old, making it the youngest known Denisovan fossil – a clue that the species was relatively recent. Scientists thought before.

Due to the paucity of fossil evidence, details about how these early human ancestors lived are limited. But still A new study It reveals that the Denisovans who lived in the Pythia karst cave were incredibly resilient, surviving one of Earth’s most extreme environments in hot and cold periods and maximizing the variety of animal resources available in the steppe landscape.

“We know that Denisovans lived and occupied the cave and this Tibetan plateau for so long, and we want to know how they lived there? How did they adapt to the environment?” said Dongju Zhang, an archaeologist and professor at Lanzhou University in China, and co-author of the study published Wednesday in the journal Nature.

“They used all these animals that were available to them, so their behavior was flexible,” Zhang added.

The rib belongs to a Denisovan, who probably lived at a time when modern humans were dispersing across the Eurasian continent, said Frido Welker, an associate professor in the Biomolecular Paleoanthropology Group at the Globe Institute at the University of Copenhagen. He said future research at the site and in the region could shed light on whether the two groups interacted there.

“It puts this fossil (sediment) layer in a context where humans are likely to have been present over a wider region, and that’s interesting,” he said.

Denisovans were first identified more than a decade ago in a laboratory using sequences of DNA extracted from a small piece of finger bone. Since then, less than a dozen Denisovan fossils Found all over the world.

Most of them were found in the Denisova Cave in the Altai Mountains of Siberia, hence the group’s name. Genetic analysis revealed that Denisovans, like Neanderthals, were once closely related to modern humans. Traces of Denisovan DNA found in present-day humans suggest that the ancient species may have lived in much of Asia.

However, it is Not until 2019 Researchers have identified the first Denisovan fossil from outside Bayre Cave.

A toothed jawbone found by a monk in the Baishia karst cave, a sacred site for Tibetan Buddhists, is at least 160,000 years old and has a Denisovan molecular signature. DNA discovery from sediment at the site, Released a year laterIt provided further evidence that Denisovans once called the area home.

In 2022, scientists identified A tooth was found in a cave in Laos A clue that the species was placed in Southeast Asia for the first time, as a Denisovan. As with jawbone, DNA cannot be extracted from a tooth, so the researchers instead analyzed microscopic remnants of proteins that preserve it better than DNA.

The study, published Wednesday, examined more than 2,500 animal bones recovered during excavations at the Baishia Cave in 2018 and 2019.

Most of the fragments were too small to be recognized by the eye, so researchers turned to a relatively new technique called zooarchaeology through mass spectrometry (ZooMS), which allows scientists to glean valuable information from previously overlooked specimens.

Based on slight differences in the amino acid sequence of the collagen preserved inside the bone, ZooMS helped the researchers determine what kind of animal the bones belonged to.

Large and small herbivores, the analysis revealed carnivores such as hyenas. Some animals like the blue sheep are still found in the Himalayas.

Many of the bones had cut marks showing that Denisovans processed the animals for their skins, meat and bone marrow. According to the study, some bones were also used as tools.

Together, the diversity of animal species found suggests that the area around the cave was dominated by a grassy landscape with some small patches of forest — much like today, though Zhang notes that most of the animals living there now are domesticated yaks and goats.

During the painstaking process of characterizing the bones, which lasted several months, the team identified a rib fragment about 5 centimeters long. However, the resolution of protein information is not sufficient to immediately determine which type of human it belongs to. Further analysis of the preserved ancient proteins led by Welker revealed that it was Denisovan.

The rib came from a sedimentary layer from which the team had previously extracted Denisovan DNA, and Zhang said the researchers were trying to recover DNA from the new sample. That process could provide detailed genetic information about the rib’s owner and the vast Denisovan population that once lived in the area.

Archaeologist Samantha Brown said that with so little information about the Denisovans, “every find is of vital importance” and the bioarchaeological analysis carried out by the authors of the new study was “particularly insightful”. who worked on the remains of Denisova Cave.

“The young age of the fossil was certainly surprising. At this point, we have evidence of modern humans occupying sites all over Australia (up to). It really opens up the conversation about the potential for interactions between those groups as modern humans moved into Asia and the Pacific, but more evidence is needed to understand the nature of those interactions.” said Brown, who was not involved in the research.

Work continues in the Baischia karst cave, and Zhang is excavating another ancient site that may have been occupied by Denisovans or modern humans who came after them, he said.

Unlike Denisova Cave, which was occupied by early modern humans and Neanderthals and Denisovans, current evidence suggests that Denisovans were the only humans to have lived in the Paishia Karst Cave, Zhang said. It forms the Tibetan Plateau – a nickname “roof of the world” — a particularly remarkable place in the quest to answer many remaining questions about who the Denisovans were, how they came to be, how they disappeared, and their place in the human family tree.