Back in 1979, fossils turned up in China that have baffled scientists to this day. Although the bones date to just 11,000 years ago, anthropologists say their features resembles those of pre-human species thought to have disappeared much, much earlier.

According to a new study out this week in PLoS One, the thigh bone from Maludong, China, that was analyzed seems to have features of very, very old relatives—species as old as the Homo genus itself. The fossil features don't seem to overlap with either humans, Neanderthals, or what's known of the Denisovan hominid.

"At the moment we're not sure what species we have found. We only have the one femur bone, and there are very few similar bones from East Asia with which to compare it," Darren Curnoe , a professor at the University of New South Wales and a co-author on the study, said in an email. "All we can really say is that it is likely to be a pre-modern humans species and perhaps one related to Homo erectus or another early member of the human genus."

While Curnoe and his team are cautious with making a positive identification based on so little available evidence, they say the thigh bone resembles two direct human ancestors, Homo erectus and Homo habilis. There are some fossil records that place H. erectus as having lived alongside Homo sapiens, with fossils placing them around 143,000 years ago, though there's some debate as to later survivals of up to 50,000 to 70,000 years ago. The fossils could represent an even later survival, or a species descended from H. erectus or H. habilis, or even another previously unknown human relative.

"Our research points to it being one of the earliest members of Homo, the most likely candidate being Homo erectus, as its known from East Asia including China," Curnoe says. "This would make it the youngest occurrence of the species if we're correct."

The discovery at Maludong involved a few skulls and skull fragments as well as other bones. Attempts at extracting DNA from the fossils have thus far been unsuccessful, something Curnoe attributes to both charring of the bones and the humid climate of the area. But DNA alone wouldn't necessarily answer the big questions, beyond the slight possibility that it's the "archaic admixture" shown in a fossil from the Denisova Cave in Russia from a cousin species to the Neanderthal.

If the Maludong fossils are from an ancient species, they would join the Homo floresiensis (a diminutive "hobbit" species with archaic features discovered in Indonesia in 2003) as one of the few ancient cousins of humanity to survive to the modern day. It would also show that our ancient relatives survived into our very recent past. But H. floresiensis is the subject of great controversy, with some claiming that, rather than representing a new human species, it was a deformed Homo sapien. Curnoe says that the Maludong skeleton shows no signs of disease, and that the features are thus likely archaic rather than a product of medical maladies on a modern human.

For now, more fossil evidence is needed, and may be hiding elsewhere in the Yunnan province.

"It is certainly possible that the Red Deer Cave people bones represent a new species, but we still have a lot of work to do before we can confirm this to be the case," Curnoe says. "Apart from the Hobbit from Flores, at the moment there are simply no pre-modern human younger than about 100,000 years in East Asia, so we don't really have much by way of a yardstick."

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