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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 unearthed 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 are known to have lived. Their work revealed that the Denisovans could hunt, kill and process a variety of different animals large and small, including shaggy rhinos, blue sheep, wild yaks, marmots and birds.
The team of archaeologists working in the cave also discovered a rib fragment in a layer of sediment dating back between 48,000 and 32,000 years ago, making it the youngest of a handful of known Denisovan fossils – a clue that the species once existed. more recently than scientists previously thought.
Due to the paucity of fossil evidence, details about how these archaic human ancestors lived have been scarce. But the new study reveals that the Denisovans living in Baishiya Karst Cave were incredibly resilient, surviving in one of the most extreme environments on Earth during its hottest and coldest periods and maximizing the diverse animal resources available in the grassland landscape.
“We know that the Denisovans lived, occupied the cave and this Tibetan plateau for so long, we really want to know, how did they live there? How did they adapt to the environment?” said Dongju Zhang, an archaeologist and professor at Lanzhou University in China and co-lead author of the study published Wednesday in the journal Nature.
“They used all available animals, which means their behavior is flexible,” Zhang added.
The rib belonged to Denisovan, who likely lived at a time when modern humans were dispersing across the Eurasian continent, said study co-author Frido Welker, associate professor in the Biomolecular Paleoanthropology Group at the Globe Institute at the University of Copenhagen. He said future research at the site and region could clarify whether the two groups interacted there.
“That puts this fossil and the (sediment) layer in a context where we know that in the broader region humans would likely be present, and that’s interesting,” he said.
A trail of Denisovan tracks
Denisovans were first identified just over a decade ago in a laboratory using DNA sequences extracted from a small fragment of finger bone. Since then, less than a dozen Denisovan fossils have been found all over the world.
Most of them were found in the Denisova Cave in the Altai Mountains of Siberia, which is how the group got its name. Genetic analysis later revealed that Denisovans, like Neanderthals, had already interbred with modern humans. Traces of Denisovan DNA found in modern-day people suggest that the ancient species likely lived across much of Asia.
however it wasn’t until 2019 that researchers identified the first Denisovan fossil outside the namesake cave.
A jaw with teeth found by a monk in the Baishiya Karst cave, a sacred place for Tibetan Buddhists, dated back at least 160,000 years and contained a Denisovan molecular signature. The discovery of DNA in sediments at the site, published a year laterprovided further evidence that Denisovans had once called the area home.
In 2022, scientists identified a tooth unearthed in a cave in Laos as 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 researchers studied the microscopic protein remains, which preserve better 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 be identified with the naked eye, so researchers turned to a relatively new technique known as Zooarchaeology Mass Spectrometry (ZooMS), which allows scientists to extract valuable information from specimens that might have been overlooked in the past. past.
Based on small differences in the amino acid sequence of the collagen preserved inside the bone, ZooMS helped researchers determine what type of animal the bones belonged to.
Baishiya’s place in Denisovan history
In addition to large and small herbivores, the analysis revealed carnivores such as hyenas. Some of the animals, such as the blue sheep, are still common in the Himalayas today.
Many of the bones had cut marks that showed the Denisovans were processing the animals for their skins, as well as meat and bone marrow. Some bones were also used as tools, the study found.
Together, the diversity of animal species found suggests that the area around the cave was dominated by a grassy landscape with some small forested areas – similar to today, although Zhang noted that most of the animals living there today are domesticated yaks and goats. .
During the laborious process of categorizing the bones, which lasted several months, the team identified the rib fragment, which is 5 centimeters long. However, the resolution of the protein’s 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 Denisovan.
The rib came from a layer of sediment from which the team had previously extracted Denisovan DNA, and Zhang said researchers are trying to recover DNA from the new specimen. This process could provide more detailed genetic information about the owner of the rib and the Denisovan population that lived in the area.
With so little information about the Denisovans, “each discovery is of great importance” and the zooarchaeological analysis carried out by the authors of the new study was “particularly insightful”, said archaeological scientist Samantha Brown, leader of the junior paleoproteomics group at the University of Tübingen, in Germany. that she worked on the remains of Denisova Cave.
“The young age of the fossil was definitely surprising. In this period, we have evidence of modern humans occupying places as far as Australia. This really opens up conversations about the possibility of these groups interacting as modern humans moved 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 investigation.
Work continues at the Baishiya Karst Cave, and Zhang is excavating another Paleolithic site in the region that the Denisovans or modern humans who came after 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 group of humans who lived in Baishiya Karst Cave, Zhang said. This makes the Tibetan Plateau – an area nicknamed “the roof of the world” – a particularly significant location in the quest to answer the many remaining questions about who the Denisovans were, what they looked like, how they disappeared, and their place in the human family tree.
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