Skull rewrites evolution: Reanalysis of Yunxian 2 suggests Homo sapiens may have emerged outside of Africa

A million-year-old human skull suggests that the origins of modern humans may reach back far deeper in time than previously thought and raises the possibility that Homo sapiens first emerged outside of Africa.

The discovery, published in the leading scientific journal Science, was shocking even for the research team, which included scientists from a university in China and the UK’s Natural History Museum.

Scientists reached this conclusion after reanalysing a skull known as Yunxian 2, discovered in China, which was previously identified as belonging to a member of the primitive human species Homo erectus.

After applying sophisticated reconstruction techniques to the skull, scientists believe it may instead belong to a group known as Homo longi (also referred to as ‘Dragon Man’), which is closely linked to the elusive Denisovans who lived alongside our own ancestors.

This repositioning would make the fossil the closest on record to the split between modern humans and our closest relatives, the Neanderthals and Denisovans. It would radically revise our understanding of the last 1 million years of human evolution.

The skull was first unearthed in Hubei Province in 1990, in a badly crushed state and was difficult to interpret. Based on its age and some broad-brush traits, it was assigned to Homo erectus, a group that is thought to have contained direct ancestors of modern humans.

The latest work used advanced CT imaging, high-resolution surface scanning and sophisticated digital techniques to produce a virtual reconstruction of the skull. The skull’s large, squat brain case and jutting lower jaw are reminiscent of Homo erectus. However, the overall shape and size of the brain case and teeth suggest that it is more closely related to Homo longi. These species, scientists have recently argued, should be incorporated into the Denisovans.

This would push the split between our own ancestors, Neanderthals and Homo longi back by at least 400,000 years and raises the possibility that our common ancestor—and potentially the first Homo sapiens—lived in western Asia rather than Africa. Genetic evidence suggests it existed alongside them, so, say the scientists, if Yunxian 2 walked the Earth a million years ago, early versions of Neanderthals and our own species probably did too.

A computational analysis of a wider selection of fossils suggests that, over the last 800,000 years, large-brained humans evolved along just five major branches: Asian erectus, Heidelbergensis, sapiens, Neanderthals, and Homo longi (including the Denisovans).

The findings run counter to some recent analyses based on genetic comparisons of living humans and ancient DNA, meaning the conclusions are likely to be contentious.