A bone from the Baishiya Karst Cave in Tibet shows that the Denisovans lived there roughly 40,000 years ago, long after modern humans had expanded into much of Asia. Combined with previous evidence of their presence in the area 190,000 years ago, the discovery reveals a remarkable tenacity in the face of extremely harsh conditions. It also increases the chances that we won’t like the answer to the question of what ended this incredible run.
Extinct members of humans are always mysterious, but the Denisovans are especially shady. The only known fossil record of them comes from three caves, but they live on a bit in our genes, or at least in the DNA of people of Asian or Australian descent.
With so many pictures missing, any new fossil discovery is extremely precious, but it’s also likely to raise more questions than it answers, as is the case with a rib found in Baishiya.
The bone is one of over 2,500 preserved in the cave, dating from 190,000-30,000 years ago – but almost all were from prey, not humans.
Study co-author Dr Geoff Smith of the University of Reading explained in a statement; “We were able to identify that Denisovans hunted, butchered and ate a variety of animal species. Our study reveals new information about Denisovan behavior and adaptation to both high-altitude conditions and variable climates. We are just getting started to understand the behavior of this extraordinary human species”.
Most of the bones Smith and co-authors were studying are so badly fractured that previous efforts had been unable to identify their sources. However, by applying mass spectrometry to the collagen within the bones, the team was able to match 2005 of them to a species, or at least a genus, revealing much about the area’s changing ecosystem.
Among the yaks, small birds, woolly rhinos, and even blue sheep (no, not green sheep) was a single Denisovan bone. It was dated to between 48,000 and 32,000 years ago—a wide range by many standards, but enough to suggest that its owner lived during the last ice age and after modern humans had spread across Asia.
Co-author Dr Jian Wang, of Lanzhou University, said: “The current evidence suggests that it was the Denisovans, not any other human group, that occupied the cave and efficiently used all the animal resources available to them throughout their occupation.”
The discovery confirms that the Denisovans used the cave during the last ice age, as well as before. Prey continued to gather during the interglacial period, so the Denisovans were almost certainly responsible for this, even if we have no examples of their bones at that time.
Denisovan rib, broken during excavation. So far its owner is not known to have been nicknamed Adam.
Image credit: Dongju Zhang’s group (Lanzhou University).
Baishiya Cave has long been a place of pilgrimage for Buddhists, but we can only speculate whether local memories of its ancient use contributed to its being seen as sacred.
In 2019 it was discovered that the inhabitants there 160,000 years ago were Denisovans, not Neanderthals as previously thought. This marked the first finding of Denisovan bones outside the cave for which they were named. More precisely, it was perhaps the first identification of Denisovan bones elsewhere – it is likely that we have found their bones in other places and attributed them to other branches of the human family tree.
Denisova Cave is a quite forbidden place today. At the same latitude as London, it gets much colder in winter thanks to being thousands of kilometers away from the moderating effect of the oceans. Baishiya, on the eastern edge of the Tibetan Plateau, is much further south, but it’s also 3,300 meters (10,800 feet) above sea level, making it much colder still. To live there during an ice age, the Denisovans must have been extremely cold-adapted.
On the other hand, the fact that their genes are more abundant today in New Guinea proves that they could also withstand the heat. Perhaps their greatest legacy to modern humans is the genes that allow modern Tibetans to thrive in low-oxygen conditions at such altitudes.
For all this, however, the Denisovans themselves are extinct, and their DNA is a tiny fraction of the modern gene pool. “The question now arises as to when and why these Denisovans on the Tibetan Plateau became extinct,” said Dr Frido Welker from the University of Copenhagen. Considering that modern humans were well established in the surrounding areas, the answer is unlikely to be good.
The study has been published in the open access journal Nature.