Chinese scientists solve puzzle of identifying extinct group of hominins

BEIJING -- Chinese researchers have revealed the shared morphological features of Denisovans, a new branch of ancient hominins, according to a research article recently published in the journal Nature.

The researchers from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences obtained ancient protein evidence from Xujiayao hominin fossils, confirming that they belonged to Denisovans.

Denisovans are an extinct group of hominins who were first identified through DNA extracted from a tiny finger bone found in a Siberian cave in 2010.

This branch of ancient hominins interbred with modern humans and has gradually become a hot topic in paleoanthropology. However, due to the scarcity of fossil records, the academic community had been unable to reveal the shared morphological features of Denisovans.

To solve this problem, an ideal site was needed -- one where human fossils could be confirmed through molecular evidence as belonging to Denisovans, and which also has abundant hominin fossils, a clear stratigraphic context and reliable dating.

The Xujiayao site, discovered in Yangyuan county of North China's Hebei province, dating back 199,000 to 138,000 years, thus became an important lead.

The research team drilled small amounts of bone powder from damaged surfaces of Xujiayao hominin fossils and extracted endogenous proteins. Via paleoproteomic analyses, they confirmed that these Xujiayao hominins belonged to Denisovans.

On this basis, the researchers systematically summarized typical morphological features of Denisovans in terms of the cranium, mandible and teeth.

Denisovans retained some primitive features similar to those of Homo erectus, such as a low braincase and thick cranial bones, while also showing some advanced features similar to those of later Homo members, like simplified premolar occlusal surfaces.

The research team, additionally, compared the Xujiayao hominins with previously confirmed Denisovans, as well as with ancient hominins in East Asia, whose taxonomic status remains unclear.

The results suggest that other ancient hominins in East Asia during the Middle Pleistocene likely also belonged to Denisovans, extending the distribution range of Denisovans to nearly the entire East Asian continent.

The study has made the mysterious ancient human group known as Denisovans, previously identified mainly through molecular evidence, recognizable, comparable and classifiable in terms of morphology, said Fu Qiaomei, a researcher at the IVPP.