A bone from the Baishiya karst cave in Tibet suggests that the Denisovans lived there about 40,000 years ago, long after modern humans had spread into much of Asia. Combined with previous evidence of their presence in the area 190,000 years ago, the find reveals extraordinary endurance in the face of extraordinarily difficult conditions. It also increases the chances that we won’t like the answer to the question of what ended this remarkable run.
Extinct human species are always mysterious, but the Denisovans are particularly dark. The only known fossil records of them come from three caves, but they live on a bit in our genes, or at least in the DNA of people with East Asian or Australian ancestry.
With so many images missing, each new fossil discovery is incalculably rare, but also likely to raise more questions than answers, as is the case with the rib bone found at Baishiya.
The bone is one of more than 2,500 preserved in the cave dating from 190,000 to 30,000 years ago – but almost all were from prey, not humans.
Study co-author Dr Geoff Smith from the University of Reading explained in a statement; “We were able to identify that the Denisovans hunted, slaughtered and ate a number of animal species. Our study reveals new information about Denisovans’ behavior and adaptation to both high-altitude conditions and a changing climate. We are only beginning to understand the behavior of this extraordinary human species. “
Most of the bones Smith and co-authors studied were so severely fractured that previous efforts were unable to identify their sources. However, by applying mass spectrometry to the collagen in the bones, the team was able to assign 2,005 of them to a species or at least a genus, revealing much about the area’s changing ecosystem.
Among the yaks, small birds, woolly rhinoceroses and even blue sheep (no, not green sheep) was a single Denisovan bone. It has been dated to between 48,000 and 32,000 years ago—a wide range by many standards, but enough to know that its owner lived during the last ice age and after modern humans 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, who occupied the cave and made efficient use of all the animal resources available to them during their occupation.”
The discovery confirms that the Denisovans used the cave during the last ice age as well as during the previous one. Prey continued to accumulate during the interglacial period, so the Denisovans were almost certainly responsible, even though we don’t have examples of their own bones from that time.
Denisovan rib bone, broken during excavation. It is not yet known that its owner is called 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 considered sacred.
In 2019, it was shown that the inhabitants there 160,000 years ago were Denisovans, not Neanderthals, as previously thought. This marked the first discovery of Denisovan bones outside the cave for which they were named. More precisely, this was probably the first identification of Denisovan bones elsewhere – it is likely that we have found their bones in other places and assigned them to other branches of the human family tree.
Denis’s cave is a rather forbidden place today. At the same latitude as London, it is much colder in winter because it is 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 is also 3,300 meters (10,800 ft) above sea level, making it even cooler. In order to live there during the Ice Age, the Denisovans had to be extremely cold.
On the other hand, the fact that their genes are most abundant in New Guinea today proves that they could handle the heat. Perhaps their greatest legacy to modern humans is the genes that allow modern Tibetans to thrive in the low-oxygen conditions at such altitudes.
Yet the Denisovans themselves are gone, and their DNA makes up 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 of the University of Copenhagen. Since modern humans were well established in the surrounding areas by this point, the answer is probably not good.
The study is published with open access in the journal Nature.