Renewed interest in fossils could rewrite origins of human species

A crushed skull discovered decades ago in central China is reshaping our understanding of the human evolutionary tree, according to a new study. The fossil, unearthed along a riverbank in Hubei province and estimated to be one million years old, was digitally reconstructed by researchers who now believe it belongs to the same lineage as “Dragon Man” (Homo longi) and the Denisovans — a mysterious human population whose origins have long puzzled scientists.

The analysis, published on September 25 in the Science journal, suggests Denisovans may have originated much earlier than previously thought. This not only rewrites their history but also shifts the evolutionary timeline for modern humans and Neanderthals, who were until now believed to be our closest relatives.

The skull, known as Yunxian 2, was one of two fossils found in 1989 and 1990 in an area known as Yunxian in Shiyan, located in the Hubei province in central China. Both were distorted by the pressures of being buried underground for millennia, but Yunxian 2 was better preserved. Using CT scanning, light imaging, and virtual modelling, researchers separated fossilized bone from encasing rock and corrected the deformation.

“This changes a lot of thinking because 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,” said study coauthor Chris Stringer, paleoanthropologist at London’s Natural History Museum.

Previously, the skull had been tentatively identified as belonging to Homo erectus, the early human species that spread widely across the globe. Yunxian 2’s large, squat braincase resembled Homo erectus, but other features — particularly its flat, shallow cheekbones — stood apart.

Lead author Xiaobo Feng of Shanxi University explained the motivation behind re-examining the fossil: “We decided to study this fossil again because it has reliable geological dating and is one of the few million-year-old human fossils. A fossil of this age is critical for rebuilding our family tree.”

Based on comparisons with more than 100 other skulls and jawbones, the team concluded that Yunxian 2 belongs to an early ancestor of Homo longi. Genetic research has linked Homo longi to Denisovans, known from fragmentary remains and DNA traces but believed to have inhabited large parts of Asia.

The findings imply that several other puzzling fossils from China may also belong to this lineage, including specimens recently proposed as a separate species, Homo juluensis, or “huge-headed man.”

Challenging the traditional belief on human origins

Because skulls preserve distinctive anatomical features, they often play a decisive role in identifying human species. The Yunxian 2 reconstruction provided the researchers with fresh data for mapping evolutionary relationships across the last million years.

Their analysis challenges the prevailing view that Homo sapiens, Neanderthals, and Denisovans diverged from a common ancestor only 700,000 to 500,000 years ago. Instead, the study estimates that modern humans and Denisovans split about 1.32 million years ago, while Neanderthals branched off even earlier, at around 1.38 million years ago.

If correct, the results mean Denisovans were more closely related to us than Neanderthals, overturning the widely held view that Neanderthals were our nearest known evolutionary cousins. The findings would also push back the emergence of Homo sapiens by roughly 400,000 years.

Stringer acknowledged that such a radical revision of the human family tree will face scrutiny. “We anticipate skepticism,” he noted, adding that the team plans to expand the dataset, including more fossils from Africa, to test and refine their conclusions.

The study also touches on a larger unresolved debate: where exactly did the ancestral populations of modern humans, Neanderthals, and Denisovans live? Africa remains the widely accepted “cradle of humankind,” but the new findings leave open the possibility that some crucial evolutionary branching occurred elsewhere.

For now, the Yunxian 2 skull contributes to what paleoanthropologists call the “muddle in the middle” — the difficult-to-classify array of human fossils dating from 1 million to 300,000 years ago. “A fossil of this age is critical for rebuilding our family tree,” Feng emphasized, underscoring how much remains unknown about our origins.

By Nazrin Sadigova