A recent digital reconstruction of a skull estimated to be a million years old is leading researchers to reconsider the timeline of human evolution, suggesting that humans may have diverged from their ancient ancestors approximately 400,000 years earlier than previously thought and potentially in Asia rather than Africa.
The study, published in the journal Science, centers on a crushed skull known as Yunxian 2, discovered in China in 1990. Experts believe these findings could shed light on the longstanding puzzle referred to as the ‘Muddle in the Middle’ regarding human evolutionary history.
Researchers revealed that Yunxian 2, which was initially believed to belong to Homo erectus, actually displayed characteristics that align more closely with later species, such as Homo longi, recently discovered, and Homo sapiens.
Chris Stringer, an anthropologist at the Natural History Museum in London, who contributed to the research, remarked, “This changes a lot of thinking. It suggests that by 1 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 findings came as a surprise to the research team. Xijun Ni, a professor at Fudan University and co-leader of the analysis, expressed astonishment 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?” he said. “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.”
If these findings hold true, they suggest the existence of earlier members of other early hominins, including Neanderthals and Homo sapiens, prior to this reconstructed timeline.
Michael Petraglia, director of Griffith University’s Australian Research Centre for Human Evolution, who was not directly involved in the study, commented, “There’s a big change potentially happening here, where east Asia is now playing a very key role in hominin evolution.” He noted that these results could challenge the long-held assumption that early humans dispersed exclusively from Africa.
Using advanced technologies such as CT scanning, structure light imaging, and virtual reconstruction techniques, the research team modeled a complete version of the Yunxian 2 skull. The team created 3D printed replicas for further analysis, comparing them to over 100 other specimens.
The reconstructed model of Yunxian 2 exhibits a unique combination of traits. Some characteristics resemble Homo erectus, such as a projecting lower face, while other current features, such as a seemingly larger brain capacity, align more closely with Homo longi and Homo sapiens.
“Yunxian 2 may help us resolve what’s been called the ‘Muddle in the Middle,’ the confusing array of human fossils from between 1 million and 300,000 years ago,” Stringer highlighted in a press release.
Despite the impressive nature of the work, much about human evolution remains hotly debated within the scientific community. Petraglia acknowledged that while the study’s findings were intriguing and grounded in robust research, he believed that many questions would emerge as a result.
Archaeologist Andy Herries of La Trobe University expressed skepticism about the conclusions, stating that previous genetic analyses have indicated that fossil morphology doesn’t always accurately reflect human evolutionary relationships. “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 remarked.
Dr. Aylwyn Scally, an evolutionary geneticist at Cambridge University, echoed the sentiment regarding uncertainty. He indicated that although the study’s conclusions seem reasonable, more evidence is required to establish further credibility. “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 stated.
These findings contribute to a series of recent studies that have complicated our understanding of human origins. Notably, Homo longi, also referred to as ‘Dragon Man,’ was identified as a new species and close human relative only in 2021 by a team that included Stringer.
The authors of the current research underscore the intricate nature of our shared evolutionary history. Stringer concluded, “Fossils like Yunxian 2 show just how much we still have to learn about our origins.”
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