Thousands of years ago in a region of southern China, different species of ancient humans might have been mixing a lot more than previously thought. Researchers studying a piece of thigh bone found in China suggest that an ancient species of human, once thought to have gone extinct tens of thousands of years ago, might have survived until the last ice age, just 14,000 years ago. This would mean it would have lived in the same region during the time when it was inhabited by four other species of human.

The new study relates to a fragment of thigh bone that has been sitting in a museum for the last 25 years. Originally found in Maludong – or Red Deer Cave – in the Chinese province of Yunnan in 1989, the piece of bone might initially seem quite unremarkable. But researchers studying the fragment have suggested that the morphology of the piece indicates that it could actually be from a “pre-modern" human. 

According to the researchers, the long, slender form of the bone and buttressing near the top resembles that found in pre-modern humans such as Homo habilis or Homo erectus, both of which were much more primitive looking. It was previously thought that these species of ancient humans went extinct around 1.5 million and 70,000 years ago, respectively.

“Its young age suggests the possibility that primitive-looking humans could have survived until very late in our evolution, but we need to careful as it is just one bone,” said Professor Ji Xueping, who co-led the study published in PLOS ONE, in a statement.

If what they’re suggesting is true, then it would mean that the older species would have lived in tropical southern China overlapping in time with not only modern humans, or Homo sapiens, but also Neanderthals, the so-called “hobbits” from the island of Flores in Indonesia, and the mysterious Denisovans, who are known just from a few tiny fragments of bones and teeth found in Siberia.

“The unique environment and climate of southwest China resulting from the uplift of the Tibetan Plateau may have provided a refuge for human diversity, perhaps with pre-modern groups surviving very late,” explained Professor Ji.

The researchers are, however, very quick to add caution to their find. “The case needs to be built up slowly with more bone discoveries,” says Darren Curnoe, who also co-led the research. The fact that they’re basing this on just a single bone, and not even a whole one at that, does mean that perhaps not too much should be drawn from the study.

But with more and more insight into how ancient human species evolved, migrated, and interacted, with recent archaeological and genetic finds from the likes of South Africa and Siberia, it adds another tantalising thread to the story of our species and our ancient relatives.   

^{Image in text: The thigh bone fragment which displays primative features, and yet is only 14,000 years old. Darren Curnoe & Ji Xueping}