Protein clues link Xujiayao fossils to a distinctive Denisovan form

Proteins and shared skull features place Xujiayao and several other East Asian fossils within the Denisovan lineage.

Editorial illustration — not from the study.

Researchers examined Xujiayao fossils, which date to about 199,000 to 138,000 years ago, using palaeoproteomics and comparisons of physical features. Proteomic analysis of two specimens identified 18 proteins, including a Denisovan-specific change in the COL1A2 protein that strongly supported their affiliation with the Denisovan lineage.

The researchers also identified shared features among fossils from Xujiayao, Harbin, Jinniushan, Dali and Hualongdong. They describe Denisovans as having a low skull profile with nearly parallel side walls, a large brow ridge, a flat cheek-and-upper-jaw region and a relatively weak projection of the face.

Denisovan protein and skull clues

Proteomic analysis of two Xujiayao specimens identified 18 proteins that originated in the hominins rather than from later contamination, according to the abstract. Both specimens showed the Denisovan-specific COL1A2-996 R>K mutation, which strongly supported their assignment to the Denisovan lineage.

Morphological comparisons linked Xujiayao and Harbin fossils with other late Middle Pleistocene archaic Homo from East Asia, including Jinniushan, Dali and Hualongdong. The shared Denisovan pattern included a low cranial profile with near-parallel lateral walls, a massive supraorbital torus, a flat zygomaxillary region and weak prognathism. The fossils also combined traits seen in Homo erectus, modern humans and late Neanderthals.

A clearer Denisovan form

The study presents a combined protein and fossil-based case for recognizing a common Denisovan physical form among several East Asian hominins. That helps address the unsettled evolutionary position of Xujiayao and offers a broader description of Denisovan anatomy, including features that overlap with other human groups as well as traits that distinguish Denisovans.

Evidence and open questions

The evidence comes from palaeoproteomic analysis of two Xujiayao specimens and morphological comparisons with other East Asian late Middle Pleistocene archaic Homo fossils. The protein result strongly supports a Denisovan affiliation, while the wider assignment of fossils is based on shared physical features. The abstract does not provide the full number of morphological specimens examined or resolve every remaining question about the taxonomy and evolutionary relationships of these hominins.

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