Diverse forms of Homo, including Homo longi, coexisted during the Middle Pleistocene. Whether these fossil humans represent different species is debated. The one-million-year-old Yunxian 2 skull from China is important for understanding the genesis of Homo. In new research, paleoanthropologists restored and reconstructed the distorted Yunxian 2 fossil using recently introduced technology. Their results show that this skull displays mosaic primitive and derived features. The team’s analyses suggest that it is an early member of the Asian Homo longi lineage, which includes the Denisovans and is the main part of the sister group to the Homo sapiens lineage.
A reconstruction of Homo longi in his habitat. Image credit: Chuang Zhao.
Fossil evidence shows that, during the Middle Pleistocene, multiple Homo lineages with diverse physical forms coexisted.
Much of what is known about human evolution and archaic hominins relies on fossil skulls.
Yet many specimens from this era are damaged and/or deformed, leading to uncertainties concerning species interpretations.
For example, three hominin skulls from the site of Yunxian in China date back nearly one million years and exhibit a mosaic of primitive traits.
Two previously known Yunxian fossils, Yunxian 1 and 2, are both distorted. The recently-discovered Yunxian 3 skull is still unprepared.
In new research, Dr. Xiaobo Feng, a researcher at Shanxi University, Hubei Polytechnic University and the Hanjiang Normal University’s Institute of Yunxian Man Site, and colleagues used advanced CT scanning and digital reconstruction techniques to correct the compression and distortions in Yunxian 2.
The team’s analysis revealed a mix of previously unknown primitive and derived traits, suggesting that the fossil belongs to the Asian Homo longi clade — a sister group to Homo sapiens, which likely included the Denisovans.
Individuals within the Homo longi clade exhibit distinctive traits, including a larger braincase, narrower spacing between the eyes, a more pronounced glabellar depression, and a lower, elongated frontal bone, which are characteristics clearly visible in the Yunxian 2 fossil.
The researchers also show that Yunxian fossils are likely the oldest within the Homo longi clade, though not the most basal.
“Given its geological age of 0.94 to 1.1 million years, Yunxian is close to the theoretical time of origin of the longi and sapiens clades,” they said.
“Phylogenetically, it is nested within the Homo longi clade. However, its mosaic morphology, which retains plesiomorphies seen in Homo erectus/Homo ergaster, Kabwe, and Petralona while developing apomorphies shared with Homo longi and Homo sapiens, may preserve transitional features close to the clade’s origin.”
“The narrow temporal gap between Yunxian and deeper longi nodes suggests rapid early diversification of the longi clade, as in the sapiens and Neanderthal clades.”
A paper on the findings appears this week in the journal Science.
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Xiaobo Feng et al. 2025. The phylogenetic position of the Yunxian cranium elucidates the origin of Homo longi and the Denisovans. Science 389 (6767): 1320-1324; doi: 10.1126/science.ado9202
