The artist’s impression of the profound features of a Denisovan. Credit: Institute of Vertebrate Paleontology and Paleoanthropology/Chinese Academy of Sciences
A low, sloping forehead; large, backward-curving brow ridges; rectangular eye sockets; flat cheeks; and a moderately high nose bridge may be characteristic facial features of Denisovans, an ancient human group. Researchers reached this conclusion after examining fossilized skull fragments, teeth and jaws from northern China, including remains identified through ancient-protein analysis.
“We are finally starting to confront the Denisovans,” says Sally Wassef, a paleogeneticist at the Queensland University of Technology in Brisbane, Australia.
Denisovans were first described in 2010, after researchers sequenced genetic material from a mysterious finger bone found in a Siberian cave. The DNA did not match that of Homo sapiens or Neanderthals (Homo neanderthalensis). Since then, ancient proteins have been used to identify Denisovan remains elsewhere in Asia, including the nearly complete Denisovan skull found near Harbin, China, which helped researchers reconstruct the faces of these ancient humans.
Researchers now say they have a clearer understanding of Denisovan anatomy after analyzing physical characteristics from 20 fossil collections discovered at Xuya. Their findings are reported in Nature.1
Ancient proteins identify the remains
The Xujiaba remains are at least 130,000 years old. They were discovered in the 1970s alongside animal remains and tools, but their human origins were initially unclear. The fossils were classified as belonging to Homo juruensis.
Qiaomei Fu, a geneticist at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, and her team identified the fossils as Denisovan by analyzing ancient proteins preserved in some of the remains.
Ancient-protein analysis is a valuable complement to DNA research, Wassef says. Proteins can survive longer than DNA without completely degrading. Although DNA provides more detailed information about an individual, proteins can also reveal useful clues about biological relationships.
Fabrice Demeter, a paleoanthropologist at the University of Copenhagen, says the discovery adds to growing evidence that Denisovans were a widespread and potentially diverse human group. “This study represents a major step forward in understanding what these humans looked like and where they lived.”
Facial features of the Denisovans
Fu’s team analyzed small protein fragments called peptides from two Xuya bones and compared them with peptides found in humans and Neanderthals. The researchers identified a single amino-acid change in multiple peptides from the Xuya bones and other East Asian fossils. This change is a known genetic marker used to identify Denisovans.
No corresponding amino-acid changes were found in the human or Neanderthal samples. Taken together with the fossil evidence, the results suggest that the heavy facial features seen in the remains may be characteristic of Denisovans.
Source: www.nature.com
