A human leg bone found in southwest China has scientists scratching their head, as it appears to belong to a separate human species thought to have gone extinct thousands of years earlier, according to an article on csmonitor.com.

The researchers say the bone compares to a modern human leg bone, and they are surprised at how recently the species was still alive on the Earth.  If they are correct, it may alter our accepted version of human history.

Scientists have known that in the past, ancient human species have occupied the planet at the same time for periods, including Neanderthals and  Denisovans, and that some actually intermingled with our own species, but they thought that the last time that happened was tens of thousands of years past.

The new discovery is said to be only about 14,000 years old, and that is a real surprise, according to study author Darren Curnoe.  He added until now, they thought archaic humans had not survived past 100,000 years ago in the mainland Asia.

Dr Curnoe cautioned it was only one bone, so they need to proceed carefully, but if the bone is authentic, it means there must have been an overlap of archaic and modern humans for tens of thousands of years in southwest China.

The bone fossil was found among other fossils in Maludong, an area also known as the Red Deer Cave, and it is not the first specimen found to indicate the existence of ancient humans.  Homo florensiensis was found to have been living as late as 17,000 years ago in the Island of Flores.  That specimen was nicknamed “Hobbit”, because of its short stature.

The team has found other specimens at the same site, and published a paper in 2012 suggesting the skulls they found then represented a population of ancient humans.  They suspect this group of people would have been isolated from much of the world allowing them to survive until so recently.

David Begun, a paleoanthropologist at the University of Toronto said he wasn’t convinced this specimen was actually part of an archaic human population, adding the bone was too fragmented to make that decision.  He says you would need the head of the femur to really say something about the fossil, and that it was missing from this specimen.

Begun admits he could be wrong, but he frankly just was not convinced.  Curnoe was not surprised by Begun’s comments, saying they expected their work to receive a mixed reaction, and that some would not be convinced, regardless of what they might have found.