Denisovans (pronounced de-knee-soh-vans) are a group of ancient humans. Our first tantalising glimpse of the Denisovans came in 2010 with genetic analysis of a tooth and tiny finger bone found in a Siberian cave called Denisova. The fossil record of these mysterious humans remains extraordinarily sparse – comprising just four fragments of bone and teeth and a jawbone found in Tibet.
However, their DNA has revealed that about 765,000 years ago, they shared a common ancestor with the Neanderthals and our species, Homo sapiens. Once this ancestral population had split, our branch of the human family tree stayed in Africa while the Neanderthal/Denisovan one moved into Eurasia. By roughly 430,000 years ago, the Eurasian branch had itself split, ultimately giving rise to the Neanderthals in western Eurasia and the Denisovans in the east.
These splits weren’t permanent, though. After tens of thousands of years of independent evolution, members of the three populations met and interbred. As a result, five per cent of the Denisovan genome lives on – not in the inhabitants of Siberia but in people living thousands of kilometres to the south-east, especially in Papua New Guinea. In fact, we now know that Denisovans bred with modern humans in at least two places: in east Asia, and further south-east in Indonesia or Australasia. What’s more, most Tibetans carry a stretch of Denisovan DNA that helps them cope with limited oxygen at altitude. This suggests interbreeding between Homo sapiens and Denisovans is what allowed humans to colonise Earth’s highest plateau.
In August 2018, researchers working at the Denisova cave in Siberia made an extraordinary discovery. Genetic analysis of a sliver of bone revealed it belonged to a teenage girl who had a Neanderthal mother and a Denisovan father. “Denny”, as she was nicknamed, is the only first-generation hybrid hominin ever found. This discovery – along with the revelation that living humans contain genes from both Denisovans and Neanderthals – has fuelled a debate about how to classify these groups of Stone Age peoples. In fact, the researchers who first identified Denisovans have never claimed them to be a distinct species. Now there is a growing debate about whether Homo sapiens, Neanderthals and Denisovans are in fact all one species.