Our extinct cousins the Denisovans had a 'distinctive' appearance, new analysis reveals

The enigmatic and now-extinct Denisovans of China shared traits with Neanderthals, modern humans and Homo erectus, according to a new study that looked at ancient proteins and fossils. But the Denisovans also had several unique skull traits and genetic variants that made them a distinctive ancient human group, according to the researchers ‪—‬ and these traits have now revealed a new face for a Denisovan man.

In the study, published Oct. 21 in the journal Nature, researchers analyzed Denisovan skulls from the archaeological site of Xujiayao in northern China. The Denisovans were a group of ancient humans who lived in Asia and disappeared around 30,000 years ago. This human relative was first identified in 2010 from the DNA of a finger bone discovered in a cave in Siberia.

The Xujiayao bones and teeth were excavated in the late 1970s, long before scientists knew about the existence of Denisovans, and were initially thought to be either Neanderthals or archaic Homo sapiens due to the shape of the fossils and their age: 138,000 to 199,000 years old.

But recent advances in paleoproteomics ‪—‬ the study of bone and tooth proteins that persist longer than DNA ‪—‬ have helped researchers identify Denisovan individuals due to specific genetic variants that differentiate them from other ancient human groups.

In the new study, researchers used paleoproteomic analysis on 20 remains from Xujaiyao and determined that all of them were from Denisovans. This determination then allowed the researchers to study the skull bones closely and figure out what Denisovans might have looked like.

The Xujiayao skulls had some features similar to H. erectus, the researchers wrote, including a low and wide braincase and thick cranial bones. But they also had anatomical features more similar to those of Neanderthals and modern humans, particularly in their bicuspids (the teeth between the canines and molars). The researchers also identified some unique Denisovan cranial traits. The back of the skull, for example, was more vertical and less rounded than in Neanderthals or modern humans.

Armed with a better understanding of Denisovan skull shape from the Xujiayao fossils, the researchers compared them with East Asian Denisovan remains that some experts have assigned to other species, such as Homo juluensis and Homo longi. But the researchers identified similarities that may preclude splitting Denisovans into different species.

"This unique combination of morphological traits, distinct from H. erectus, modern humans and Neanderthal-lineage hominins, supports the assignment of most members of East Asian late Middle Pleistocene archaic Homo as Denisovans," they wrote in the study. This means that Denisovans may have been one human lineage that adapted to diverse ecological zones across Asia over hundreds of thousands of years.

"It is still possible that there are some other lineages that existed in East Asia during the time Denisovans are known to have existed," study co-author Qiaomei Fu, director of the Ancient DNA Laboratory at the Institute of Vertebrate Paleontology and Paleoanthropology, part of the Chinese Academy of Sciences, told Live Science in an email.

"We know from DNA that Denisovans were a very varied group genetically, which split early into different populations," Chris Stringer, a paleoanthropologist at the Natural History Museum in London who was not involved in the research, told Live Science in an email. "These could have developed a lot of morphological variation, which may well surprise us as the sample of fossils grows."

The researchers also produced a new reconstruction of what a Denisovan man might have looked like. A previous DNA study suggested that Denisovans likely had dark skin, brown hair and brown eyes. The new reconstruction shows the Denisovan looking directly at the viewer, with his low, wide braincase mostly obscured by dark hair flowing back from his massive brow ridge. There are clear similarities between the Denisovan man and Neanderthals as well as modern humans, but the Denisovan has a distinct visage all his own.

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