Evrim Yazgin
Cosmos science journalist
A jawbone found in Taiwan has been identified as belonging to a Denisovan. The fossil has altered perceptions about the ancient human species.
It is the first time a Denisovan fossil has been confidently identified outside central Asia.
Denisovans were first discovered in 2010. So far, only a few fossils have been confirmed using molecular analysis as belonging to Denisovans. All of these have been found in Siberia and Tibet until now.
Analysis of the Taiwan fossil is detailed in a paper published in the journal Science.
It is the first direct evidence that Denisovans occupied diverse climates from the cold Siberian mountains to the warm, humid subtropical environments of Taiwan. Up until now, palaeontologists and archaeologists had to infer that Denisovans were more widespread based on genetic links with modern humans living in other parts of Asia and Oceania.
The researchers used molecular techniques to confirm the Taiwan jawbone, or mandible, as Denisovan. They extracted 4,241 amino acid residues and identified 2 which are found in only Denisovans.
The bone belonged to a male and was dredged up by a fishing boat along with ancient animal remains in the Penghu Channel off Taiwan’s west coast.
The seafloor there was once land, connecting Taiwan with mainland Asia.
The researchers were unable to pinpoint an exact date for the bone without radiocarbon dating. They say the ancient human lived either 10,000 to 70,000 years ago or 130,000 to 190,000 years ago based on trace elements and knowledge of ancient sea levels.
Denisovans are closely related to Neanderthals. Genetic studies have shown that the 2 species diverged about 400,000 years ago. Modern humans and Neanderthals split from their common ancestor about 500,000 to 600,000 years ago. Genetic evidence shows that all 3 groups interbred.
Both Denisovans and Neanderthals are thought to have died out about 40,000 years ago.
The Denisovan fossil from Taiwan helps flesh out the appearance of these ancient humans and contrast them with Neanderthals. The authors note that the 2 groups are “small-toothed Neanderthals with tall but gracile mandibles, and large-toothed Denisovans with low but robust mandibles”.
Often Neanderthals are considered the stocky, robust cousins of modern humans. But it seems that Denisovans were even more robustly built – at least in the jaw.
The authors do say, however, that this strongly built jaw may be a sign of sexual dimorphism as the males of some other primate species do have more robust jaws than females.
“The increased fossil sample of Denisovans demonstrates their wider distribution, including warm and humid regions, as well as their shared distinct robust dentognathic traits that markedly contrast with their sister group, Neanderthals,” the authors write.
They point to other human species in the Homo genus which lived until fairly recently all having their own unique genetic adaptations, and suggest that the robust jaw of Denisovans could be another such example of divergence in our human family tree.
“Recent discoveries from insular Southeast Asia [Homo floresiensis and Homo luzonensis] and South Africa [Homo naledi] highlight the diverse evolution of the genus Homo, contrasting with the lineage leading to H. sapiens. The dentognathic morphology of Denisovans can be interpreted as another such distinct evolution that occurred in our genus,” they write.
