One-million-year skull prompts revised view of early human evolution

A one-million-year-old skull known as Yunxian 2 may push back the timeline for the emergence of large-brained humans and reshape our view of early human evolution. In a study published in Science, researchers argue that the divergence and spread of different hominid lineages occurred hundreds of thousands of years earlier than previously thought. ‘From the very beginning, when we got the result, we thought it was unbelievable. How could that be so deep into the past?’ said Prof Xijun Ni of Fudan University, who co-led the analysis.

The unreconstructed Yunxian 2 skull was found in 1990 in a repository in Hubei province, central China, and is housed at the Hubei Provincial Museum. For decades, researchers had attributed the skull to Homo erectus, given its age and appearance. But a team from China and the United Kingdom used CT scans to create digital restorations of the crushed cranium and concluded that it belongs to an early Asian hominid lineage connected to the Denisovans, an offshoot within the Homo longi clade. The Denisovans, although extinct, are known today from DNA evidence unearthed in 2010. An artist’s impression of what Yunxian 2 might have looked like one million years ago is shown in accompanying imagery.

The restored portrait of Yunxian 2, with a large cranial capacity and distinctive facial features, aligns with traits attributed to the Denisovans within the broader Homo longi clade. Study co-author Chris Stringer, a paleoanthropologist at the Natural History Museum in London, said the long-lived Denisovan lineage likely persisted for more than a million years, as did the Neanderthal and Homo sapiens lines. ‘The Homo longi clade, containing the Denisovans, lasted for over a million years,’ Stringer noted. ‘But so did the Neanderthal and sapiens lineages.’

That interpretation suggests Yunxian 2 may have lived alongside early humans in other lineages, implying that three distinct hominid groups shared the planet at roughly the same time. If the analysis holds, large-brained humans could have emerged about a half-million years earlier than thought. Ni emphasized that the team tested multiple models and remained careful about the conclusions, saying they’re excited but not claiming certainty.

The new view, however, is not without caveats. Experts cautioned that dating methods and skull-based taxonomic assignments can be tricky, particularly for such ancient specimens. ‘One has to be particularly tentative about the timing estimates, because those are very difficult to do, regardless of what evidence you’re looking at, be that genetic or fossil evidence,’ said Dr Aylwyn Scally, an evolutionary geneticist at Cambridge University. He stressed that placing coexistence of these populations within a narrow window remains challenging and could be revised with further data.

Stringer himself acknowledges the possibility of earlier Homo sapiens fossils in Asia, but he cautions that there is not yet enough evidence to confirm such a shift in our understanding. The new analysis coincides with a growing recognition that multiple hominid groups may have interacted or existed in parallel at times when climate and geography created isolated, diverse populations. Stringer also notes that the timing of these events must be interpreted with awareness of potential margin errors that can stretch to hundreds of thousands of years.

If Yunxian 2 indeed belongs to a Denisovan-leaning lineage, the discovery strengthens the view that significant diversification occurred early in human evolution, coinciding with major climatic swings. Scientists point to two severe cold events dating to about 1.1 million and 900,000 years ago as possible catalysts for rapid evolution and behavioral shifts across populations. These environmental stresses could have driven adaptations and migrations that shaped the later paths of Homo sapiens, Neanderthals and Denisovans alike. Yet, researchers caution that pinpointing causation remains speculative without additional fossils and corroborating genetic data.

The study’s authors acknowledge that the assertion of a Denisovan-related Denisovan-Homo longi lineage in Asia around one million years ago remains an interpretation subject to revision. While the result fogs a more complex prehistory than previously recognized, continued fossil discoveries and advances in dating techniques will be essential to confirm or adjust the timeline. Africa’s role as the cradle of Homo sapiens remains supported by current evidence, with the earliest widely accepted Homo sapiens fossils in Africa dating to roughly 300,000 years ago, a point cited by several researchers when discussing global migration patterns.

The Yunxian 2 finding underscores how modern imaging and comparative anatomy can reopen debates about ancient species boundaries and geographic ranges. While the mystery of who Homo sapiens were alongside in Asia a million years ago is far from settled, the study adds to a growing willingness in the scientific community to revisit long-held assumptions about when and where our species emerged and diversified. Further discoveries could either reinforce this bold revision or refine it as new data come to light. As researchers continue to piece together this puzzle, the possibility that humanity’s roots extend even deeper into the past remains an open and debated frontier.