Ancient proteins offer new clues to what Denisovans looked like.
Researchers say proteins from two fossils at the Xujiayao site link them to the Denisovan lineage, and a skull comparison points to a distinctive set of Denisovan features.
A research team reports that ancient proteins recovered from fossils at Xujiayao tie those specimens to the Denisovan lineage. The authors also compared skull features across several East Asian fossils and describe a set of traits they say outlines what Denisovans looked like.
The paper begins with an unsettled question. According to the authors, the classification and family tree of late Middle Pleistocene hominins in East Asia remain highly debated. Xujiayao is described as a key assemblage with many fossils and a clear stratigraphy, dated to about 199 to 138 thousand years ago. It has been studied extensively, but its evolutionary position had stayed uncertain.
To address this, the team combined palaeoproteomic analysis, which studies ancient proteins, with morphological comparisons against other East Asian archaic Homo from the same broad period. Proteomic analysis of two Xujiayao specimens identified 18 endogenous proteins. The authors report that a Denisova-specific mutation, called COL1A2-996 R>K, strongly supported placing the specimens in the Denisovan lineage.
The researchers then extended the analysis to skull shape. They identified shared traits between Denisovan fossils (Xujiayao and Harbin) and other East Asian late Middle Pleistocene fossils, including Jinniushan, Dali and Hualongdong. On that basis, they conclude that all of these fossils belong to the Denisovan lineage.
The resulting picture is a mixture. Denisovans show traits reminiscent of Homo erectus, such as a thick cranial vault, and traits characteristic of modern humans, for example a strongly arched temporal squama. They also share features with late Neanderthals, including the structure of the temporal labyrinth and the presence of a suprainiac fossa.
The authors say Denisovans are nonetheless distinctive. Their listed features are a low cranial profile with near-parallel lateral walls, a massive supraorbital torus, a flat zygomaxillary region and weak prognathism. The authors present this as a comprehensive view of Denisovan features.
At a Glance
- Xujiayao fossils date to around 199 to 138 thousand years ago, according to the paper.
- Proteomic analysis of two Xujiayao specimens identified 18 endogenous proteins.
- The Denisova-specific COL1A2-996 R>K mutation strongly supported a Denisovan affiliation for the specimens.
- Jinniushan, Dali and Hualongdong fossils share traits with Xujiayao and Harbin, which the authors place in the Denisovan lineage.
Sources
This brief was written by Brightside Report from the reporting linked above. Spot an error? Request a correction.