For decades, the story of human evolution has been dominated by discoveries in Africa, with the continent widely regarded as the cradle of humanity. But a crushed skull unearthed in 1990 from a river terrace in China’s Hubei province is now challenging some of those long-held beliefs and sending shockwaves through the world of paleoanthropology. The fossil, known as Yunxian 2, has been digitally reconstructed using cutting-edge technology, and the results, published this week in Science, suggest our evolutionary timeline may need a serious rewrite.
The story begins nearly 35 years ago, when archaeologists excavated the Yunxian 2 cranium from the banks of the Hanjiang River. At the time, the skull’s deformed and crushed state left researchers uncertain about its exact place in the human family tree. Initial studies classified it as Homo erectus, the first species to exhibit a human-like body and stride. But the fossil’s true significance would remain hidden for decades, waiting for technology to catch up.
Fast forward to the present, and a team of international scientists has finally been able to digitally reconstruct the Yunxian 2 skull using advanced CT scanning, structured light imaging, and 3D modeling. The process corrected the warping and compression caused by fossilization, revealing a remarkably complete picture of an ancient hominin. As BBC News reports, the researchers compared their model to over 100 other fossil specimens, using another similar skull to help shape their reconstruction.
The results were nothing short of astonishing. The reconstructed cranium appeared large and elongated, with a broad, flat braincase. It exhibited a “mosaic” of traits: some primitive features reminiscent of Homo erectus—such as a projecting lower face and thick brow ridges—alongside characteristics typically seen in much later hominins, including Homo sapiens and the recently discovered Homo longi. According to the research team, “the cranium is clearly plesiomorphic in overall form, presenting primitive traits shared by earlier hominins.”
But it was the unique combination of features that truly set Yunxian 2 apart. The skull lacked the strongly angled occipital bone seen in H. erectus and the protruding occipital region of Neanderthals. Instead, it had a larger braincase, narrower spacing between the eyes, and an elongated frontal bone—traits that are “clearly visible” in the digital reconstruction and are hallmarks of the Homo longi lineage. As Archaeology Magazine notes, this mixture of primitive and advanced traits positions Yunxian 2 as a potential transitional form between Homo erectus and later human groups.
Phylogenetic analysis placed Yunxian 2 firmly within the Homo longi clade, a group that likely includes the enigmatic Denisovans and is considered a sister lineage to modern humans. This is a big deal, because it implies that the evolutionary split between these groups happened much earlier than previously believed. As Science X explains, earlier estimates put the divergence between modern humans and Neanderthals at around 500,000 to 700,000 years ago. But the new findings suggest Neanderthals split off some 1.38 million years ago, followed by the separation of the longi and sapiens clades at approximately 1.32 million years ago. Distinctive Homo longi features appeared around 1.2 million years ago, while the earliest Homo sapiens traits emerged about 1.02 million years ago.
“This changes a lot of thinking,” said Chris Stringer, an anthropologist at the Natural History Museum in London and a member of the research team, as quoted by AFP. “It suggests that by one million years ago, our ancestors had already split into distinct groups, pointing to a much earlier and more complex human evolutionary split than previously believed.”
The implications are profound. If the findings hold up, they could push back the emergence of Homo sapiens by hundreds of thousands of years and challenge the prevailing notion that early humans dispersed solely from Africa. “There’s a big change potentially happening here, where east Asia is now playing a very key role in hominin evolution,” said Michael Petraglia, director of Griffith University’s Australian Research Centre for Human Evolution, who was not involved in the study. He told AFP that the discovery “muddies the waters” on long-standing assumptions about human origins.
The study’s co-leader, Xijun Ni of Fudan University, expressed initial disbelief at the results. “From the very beginning, when we got the result, we thought it was unbelievable. How could that be so deep into the past?” Ni told BBC News. “But we tested it again and again to test all the models, use all the methods, and we are now confident about the result, and we’re actually very excited.”
Of course, not everyone is convinced. The findings have sparked debate among experts, some of whom caution that the conclusions may be premature. Andy Herries, an archaeologist at La Trobe University, argued that fossil shape alone is “not always a perfect indicator for human evolution,” pointing out that genetic analysis sometimes tells a different story. “They’ve got this interpretation that I just don’t really think is taking into account the genetic histories of these things that we do know,” he told AFP.
Dr. Aylwyn Scally, an evolutionary geneticist at Cambridge University, echoed this skepticism, telling BBC News that while the study’s conclusions are plausible, more evidence—ideally from genetic data—is needed before the new timeline can be accepted. “That picture is still quite unclear to us, so if the conclusions of this research are supported by other analyses, ideally from some genetic data, then I think we would start to be increasingly confident about it,” he said.
The discovery of Yunxian 2 comes amid a flurry of recent research that has complicated the story of our origins. Homo longi itself was only named as a new species and close human relative in 2021 by a team that included Stringer. The authors of the new study argue that their work illustrates the complexity and branching nature of our shared history. “Fossils like Yunxian 2 show just how much we still have to learn about our origins,” said Stringer.
What’s clear is that the Middle Pleistocene period—between 1 million and 300,000 years ago—was a time of rapid diversification and coexistence among multiple hominid species. Fossil sites from China, the Philippines, South Africa, and elsewhere reveal a high degree of morphological diversity, raising questions about whether these remains represent separate species or simply variations along the lineage leading to modern humans. The Yunxian 2 skull, with its blend of ancient and modern traits, sits close to the theoretical origin of both the longi and sapiens clades, potentially capturing a snapshot of this evolutionary branching in action.
As the dust settles, one thing is certain: the story of human evolution is far from complete, and every new discovery—like Yunxian 2—adds another twist to our ever-evolving understanding of where we come from.
