A new study has corrected distortions and fractures in China’s Yunxian 2 cranium and suggests the fossilised skull belonged to the clade Homo longi – a sister lineage to modern humans (Homo sapiens).
Yunxian 2 and another skull, Yunxian 1, were unearthed from the Hanjiang River in the Yunyang district of Shiyan City, China. They date to between 0.94 and 1.10 million years ago during the Middle Pleistocene, when fossil evidence suggests many different species of humans coexisted.
Reconstruction of the Yunxian 2 cranium. Brown indicates fossilised bone. Dark brown indicates reconstruction using elements of Yuxian 1. White is reconstructed parts inferred from the fracture edge and Yunxian 1. Grey indicates bones crushed and covered by other bones. Scale bar 5cm. Credit: Feng et al 2025, Science
“It remains a matter of intense debate whether these morphologically diverse archaic humans represent multiple evolutionary clades or whether they are transitional variants leading to H. sapiens,” write the authors of a paper presenting the research in the journal Science.
“Our understanding of human evolution is largely based on fossil cranial specimens, but many of these are incompletely preserved and/or distorted. Proper reconstruction of these imperfect fossils is therefore critical to studying their phylogenetic relationships.”
Yunxian 1 is crushed and exhibits obvious plastic deformation which, according to the researchers, involves the “twisting, banding, or flattening of a curved surface when subjected to continuous force or stress”.
The distortion of Yunxian 2 is much less severe, consisting mainly of small fractures and large missing fragments.
The researchers used CT scanning and digital reconstruction techniques, with some additional data from Yunxian 1, to correct the skull.
This revealed that Yunxian 2 exhibits distinctive traits found in the H. longi clade. This included a larger braincase, narrower spacing between the eyes, a more pronounced depression in the area between the eyebrows and a lower, elongated forehead.
Grey lines show the phylogenetic (evolutionary tree) relationships between the Yunxian 2 fossil and recent Homo specimens. H. longi clade indicated in purple. Credit: Feng et al 2025, Science
By comparing the shape of Yunxian 2 to 26 of the most complete hominin fossils and 153 recent human specimens, they showed it shares a close evolutionary relationship with Asian hominins in the H. longi clade.
“Both the H. sapiens and H. longi clades have deep roots extending beyond the Middle Pleistocene and probably experienced rapid early diversification,” the authors conclude.
“Yunxian 2 may preserve transitional features close to the origins of the 2 clades.”