How Denisovans survived and thrived on the ‘roof of the world’

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The Denisovans survived and thrived on the high-altitude Tibetan Plateau for more than 100,000 years, according to a new study that deepens scientific understanding of the mysterious ancient people first identified in 2010.

Scientists have analyzed thousands of animal bone fragments discovered in the Baishiya karst cave, 3,280 meters above sea level near the city of Xiahe in China’s Gansu province – one of only three places where extinct humans lived. Their work revealed that the Denisovans could hunt, cut and process a variety of large and small animals, including woolly rhinoceroses, blue sheep, wild yaks, marmots and birds.

A team of archaeologists working in the cave also uncovered a fragment of a rib bone in a layer of sediment that dates back to between 48,000 and 32,000 years ago, making it the youngest of a handful of known Denisovan fossils—a clue that the species was more recent than scientists previously thought. they thought.

Due to the lack of fossil evidence, details about how these archaic ancestors of humans lived are scarce. But a new study reveals that the Denisovans who lived in the Baishiya karst cave were incredibly hardy, surviving in one of Earth’s most extreme environments during warmer and colder periods and maximizing the diverse animal resources available in the grassy landscape.

“We know that the Denisovans lived, inhabited the cave and this Tibetan plateau for so long, do we really 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 a study published Wednesday in the journal Nature.

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

The rib belonged to a Denisovan, who likely lived around the time modern humans dispersed across the Eurasian continent, said study co-author Frido Welker, an associate professor in the Globe Institute’s Biomolecular Paleoanthropology Group 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 and the (sedimentary) layer in a context where we know humans were probably present in the wider area, and that’s interesting,” he said.

Denisovans were first identified more than a decade ago in the laboratory using DNA sequences extracted from a small fragment of a finger bone. Since then, fewer than a dozen Denisovan fossils have been found worldwide.

Most of them were found in the Denisova Cave in the Altai Mountains of Siberia, from which the group got its name. Genetic analysis subsequently revealed that Denisovans, like Neanderthals, once interbred with modern humans. Traces of Denisovan DNA found in modern humans indicate that the ancient species probably once lived in much of Asia.

However, it was not until 2019 that scientists identified the first Denisovan fossil outside the cave of the same name.

A jawbone with teeth found by a monk in the Baishiya karst cave, a sacred site for Tibetan Buddhists, was at least 160,000 years old and contained a Denisovan molecular signature. The discovery of DNA from sediment at the site, published a year later, provided further evidence that the Denisovans once called the area home.

In 2022, scientists identified a tooth discovered in a cave in Laos as a Denisovan, a clue that placed the species in Southeast Asia for the first time. As with the jawbone, DNA could not be extracted from the tooth, so the researchers instead studied the microscopic remains of proteins, which are better preserved than DNA, although less informative.

A study published Wednesday examined more than 2,500 pieces of animal bone recovered during excavations at Baishiya Cave in 2018 and 2019.

Most of the fragments were too small to be identified by eye, so the researchers turned to a relatively new technique known as Zooarchaeology by Mass Spectrometry (ZooMS), which allows scientists to extract valuable information from samples that might have been overlooked in the past .

Based on small differences in the amino acid sequence of the collagen preserved inside the bone, ZooMS helped scientists determine which type of animal the bones belonged to.

In addition to large and small herbivores, the analysis also revealed carnivores such as hyenas. Some animals, such as the blue sheep, are common in the Himalayas even today.

Many of the bones had cut marks showing that the Denisovans processed the animals for their hides as well as their meat and bone marrow. Some of the bones were also used as tools, according to the study.

The diversity of animal species found suggests that the area around the cave was dominated by a grassy landscape with small forested areas – similar to today, although Zhang noted that most of the animals living there today are domesticated yaks and goats.

During the painstaking process of categorizing the bones, which took several months, the team identified a rib bone fragment that is 5 centimeters long. However, the resolution of the protein information was not clear enough to immediately determine what kind of person it belonged to. Further analysis of the preserved ancient proteins by Welker revealed that it was Denisovan.

The rib bone came from a layer of sediment from which the team had previously extracted Denisovan DNA, and Zhang said the researchers were trying to obtain DNA from the new sample. This process could provide more detailed genetic information about the rib’s owner and the wider Denisovan population that once lived in the area.

With so little information about the Denisovans, “every discovery is very important,” and the zooarchaeological analysis by the authors of the new study was “particularly insightful,” said archaeologist Samantha Brown, head of the paleoproteomics junior group at Germany’s University of Tübingen. who worked on the remains from Denis’s cave.

“The low age of the fossil was definitely surprising. In this time period we have evidence of modern humans occupying sites as far away as Australia. “This really opens up conversations about the possibility of interactions between these groups as modern humans migrated into Asia and the Pacific, but more evidence will likely be needed to understand the nature of these interactions,” said Brown, who was not involved in the research.

Work continues at Baishiya Karst Cave, and Zhang is excavating other Paleolithic sites in the region that may have been occupied by the Denisovans or modern humans who came after them, she said.

Unlike Denisova Cave, which was occupied by early modern humans and Neanderthals as well as Denisovans, current evidence suggests that Denisovans were the only group of people living in Baishiya Karst Cave, Zhang said. This makes the Tibetan Plateau – an area dubbed the “roof of the world” – a particularly important location in the search for answers to the many remaining questions about who the Denisovans were, what they looked like, how they disappeared and what their place is on the human body. pedigree.