For over a century, Neanderthals have been extensively studied through their bones, artifacts, and their distribution across Eurasia. Their genome sequence revealed our shared genetic legacy with them, situating these discoveries in a broader context. In stark contrast, the existence of Denisovans was unknown until DNA sequencing from a small finger bone uncovered another ancient human relative in Asia.
Since then, our knowledge of Denisovans has remained limited. Their DNA in modern human populations suggests they were likely concentrated in East Asia. However, only fragments of bones and a few teeth have been found, leaving us with scant information about their appearance. Recently, an international research team discovered more about Denisovans from a cave on the Tibetan Plateau, providing insights into their diet and survival.
The Baishiya Karst Cave
The Baishiya Karst Cave, located over 3,000 meters (nearly 11,000 feet) above sea level on the northeast Tibetan Plateau, borders a high open plain. This cave, a pilgrimage site for Tibetan monks, came to paleontologists’ attention when a monk discovered a portion of a lower jaw, now known as the Xiahe mandible. This jawbone, analyzed for protein content, was identified as Denisovan and remains the most substantial Denisovan fossil to date.
Subsequent excavations at Baishiya Karst Cave uncovered numerous animal bones, but no definitive Denisovan bones were initially identified. Environmental DNA sequencing from the cave indicated that Denisovans had occupied it regularly for at least 100,000 years, surviving at high altitudes during the last two glacial cycles.
The Denisovan Diet
The latest research focused on the bone fragments found in the cave. Using a technique called zooarchaeology by mass spectrometry (ZooMS), researchers identified nearly 80% of the tested bone fragments. This method involves purifying protein fragments from bones and analyzing them using mass spectrometry to determine their species origin.
The analysis revealed that many species met their end in the Baishiya Karst Cave. The most common species was the bharal, or blue sheep, prevalent in the Himalayas. Other identified species included yaks, horses, gazelles, deer, woolly rhinoceros, flying squirrels, porcupines, spotted hyenas, wolves, snow leopards, pheasants, and golden eagles.
Significantly, many bones showed signs of butchering, such as muscle cut marks and broken bones for marrow extraction. Predator damage was minimal, indicating that Denisovans were not merely scavenging but actively hunting. Over time, the frequency of certain species, particularly sheep, increased, suggesting a shift toward specialized hunting.
Another Denisovan Bone
Among the bones, researchers identified a fragment belonging to a Denisovan, making it one of the largest Denisovan bone samples found. This rib fragment, about 5 centimeters long, came from a cave layer where previous DNA analysis had not detected Denisovan presence, suggesting that Denisovans were present on the Tibetan Plateau as recently as 30,000 years ago.
Despite these findings, much about the Denisovans remains unknown, including their appearance and the full scope of their diet. However, the discoveries highlight their remarkable ability to survive in harsh, high-altitude climates over two glacial periods, a trait they may have passed to present-day inhabitants of the Tibetan Plateau.
Conclusion
The findings from Baishiya Karst Cave enrich our understanding of Denisovans, their adaptability, and their diet. This high-altitude cave, once a site for Tibetan Buddhists, now offers crucial insights into the lives of these ancient human relatives, showcasing their survival skills in one of the planet’s most challenging environments.