Million-year-old Chinese skull challenges timeline of human evolution

A million-year-old human skull discovered in China implies that our species, Homo sapiens, emerged at least half a million years earlier than previously thought, according to new research.

It also demonstrates that we coexisted alongside other sister species, including Neanderthals, for far longer than previously thought, they claim.

The scientists argue that this "totally changes" our understanding of human evolution, and if right, it would undoubtedly rewrite an important early chapter in our history.

However, experts say that these conclusions are only probable, not conclusive.

The skull, now termed Yunxian 2 by the researchers, was formerly assumed to be that of Homo erectus, a human predecessor.

However, using contemporary reconstruction tools, the researchers revealed traits that are more similar to species traditionally assumed to have existed later in human development, such as the recently discovered Homo longi and our own Homo sapiens.

If the findings are right, they suggest that other early hominins, such as Neanderthals and our own Homo sapiens line, may have existed considerably earlier. However, other scientists say that it "muddies the waters" on long-held theories about how early humans dispersed beyond Africa. 

The study, published in the journal Science, uses advanced CT scanning, structural light imaging, and virtual reconstruction techniques to recreate the entire Yunxian 2.

The scientists used another comparable skull to help shape their model, which they then compared to over 100 other skulls.

The final model "shows a distinctive combination of traits," the study stated, some of which are similar to Homo erectus, such as a protruding lower face.

However, other characteristics, such as its apparent bigger brain capacity, are more akin to Homo longi and Homo sapiens, the researchers added.

"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," Chris Stringer, an anthropologist at the Natural History Museum, London, who was part of the research team, said in a press release.