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

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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 enigmatic ancient humans first identified in 2010.

Researchers analyzed thousands of animal bone fragments discovered in the Baishiya karst cave, 11,000 feet (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 Denisovans may have hunted, butchered and processed a range of small and large animals, including woolly rhinos, blue sheep, wild yaks, marmots and birds.

The team of archaeologists working in the cave also discovered a rib bone fragment in a layer of sediment dated to between 48,000 and 32,000 years ago, making it the youngest of a handful of known Denisovan fossils — a hint that the species was around more recently than scientists previously thought.

Due to the lack of fossil evidence, details about the lifestyles of these archaic human ancestors have remained scarce. But the new study reveals that the Denisovans who lived in the Baishiya karst cave were incredibly resilient, surviving in one of Earth’s most extreme environments during both warmer and colder periods and maximizing the diverse animal resources available in the grassland landscape.

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

“They used all the animals at their disposal, which means their behavior is flexible,” Zhang added.

The coast belonged to Denisovans, who likely lived at a time when modern humans were spreading across the Eurasian continent, said Frido Welker, a co-author of the study and an associate professor in the biomolecular paleoanthropology group at the Globe Institute at the University of Copenhagen. He added that 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 (sediment) layer into a context where we know that in the broader region, humans were likely present, and that’s interesting,” he said.

Denisovans were first identified a little over a decade ago in a lab from DNA sequences extracted from a tiny fragment of finger bone. Since then, fewer than a dozen Denisovan fossils have been discovered worldwide.

Most of these specimens were discovered in Denisova Cave in the Altai Mountains of Siberia, hence the group’s name. Genetic analyses later revealed that Denisovans, like Neanderthals, had once interbred with modern humans. Traces of Denisovan DNA found in modern humans suggest that this ancient species likely once lived across much of Asia.

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

A jawbone with teeth discovered 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 in sediment from the site, published a year later, provided further evidence that Denisovans once called the area home.

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

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

Most of the fragments were too small to identify with the naked 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 specimens that might have been overlooked in the past.

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

The analysis revealed the presence of herbivores of all sizes, but also carnivores such as hyenas. Some of these animals, such as the blue sheep, are still common in the Himalayas today.

Many of the bones showed signs of cutting that showed Denisovans processed animals for their skins, meat and bone marrow. Some bones were also used as tools, the study said.

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

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

The rib bone comes from a layer of sediment from which the team had previously extracted Denisovan DNA. Zhang said the researchers are trying to recover the DNA from the new specimen. This process could provide more detailed genetic information about the owner of the rib and the broader Denisovan population that once lived in the area.

With so little information about the Denisovans, “every find is of major importance,” and the zooarchaeological analysis by the authors of the new study was “particularly illuminating,” said archaeologist Samantha Brown, junior group leader of paleoproteomics at Germany’s University of Tübingen, who worked on the Denisova Cave remains.

“The early age of the fossil is really surprising. At that time, we have evidence that modern humans were occupying sites as far away as Australia. It really opens up discussions about the possibility that these groups interacted as modern humans moved into Asia and the Pacific, but more evidence is likely needed to understand the nature of those interactions,” said Brown, who was not involved in the research.

Work continues at the Baishiya karst cave, and Zhang is excavating another Paleolithic site in the area that Denisovans or the modern humans who followed them may have occupied, 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 human group to live in Baishiya Karst Cave, Zhang said. That makes the Tibetan Plateau — a region dubbed “the roof of the world” — a particularly important place in the quest to answer the many questions that remain about who the Denisovans were, what they looked like, how they disappeared and where they fit into the human family tree.