Abstract:

Late Middle Pleistocene hominins in East Asia exhibit considerable morphological diversity, and their taxonomic classification and evolutionary relationships have long remained controversial. Among them, the Xujiayao site has yielded relatively abundant hominin fossils from a well-defined stratigraphic context, yet their phylogenetic position has remained unresolved. To address this issue, the research team led by Qiaomei Fu and researcher Song Xing at the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, in collaboration with several institutions, conducted an integrated paleoproteomic and morphological study of the Xujiayao hominin fossils dated to approximately 199–138 ka. The researchers identified 18 endogenous ancient proteins from two Xujiayao skeletal samples and confirmed their assignment to the Denisovan lineage through a Denisovan-characteristic single amino acid polymorphism (COL1A2-996K) and phylogenetic analyses. Building on this molecular identification, they further compared the morphology of Denisovan fossils, including those from Xujiayao and Harbin, and identified a series of similar morphological traits among other East Asian late Middle Pleistocene hominins, including those from Jinniushan, Dali, and Hualongdong, suggesting that these hominins may also belong to the Denisovan lineage. The study systematically characterized Denisovan cranial morphology, revealing a mosaic of Homo erectus-like primitive traits, derived traits shared with modern humans, features shared with late Neanderthals, and distinctive Denisovan characteristics. These findings provide direct molecular evidence for resolving the long-debated taxonomic status of the Xujiayao hominins, substantially enrich our understanding of Denisovan morphological phenotypes, and offer important insights into reassessing the classification and evolutionary relationships of East Asian late Middle Pleistocene hominins.

Key words: Denisovans, paleoproteomics, morphology, Xujiayao hominins, Middle Pleistocene