

A 14,000-year-old fragment of thigh bone found in a cave in China may represent evidence of the unexpected survival of long-vanished human ancestors.

If so, then right into and through the ice age, a creature that was either Homo habilis or Homo erectus survived alongside the Neanderthals, the unknown humans who left behind some DNA in a cave in Siberia, the mysterious so-called hobbit of the island of Flores in Indonesia, and modern Homo sapiens.

But by the end of this multicultural ice age 10,000 years ago, only one human species survived.

The fossil, a partial femur, had survived unstudied for at least 25 years in a museum in southeastern Yunnan in China. It was one of a set of fossilised remains found in the Maludong Cave – it means Red Deer Cave – in 1989. Darren Curnoe, a palaeoanthropologist from the University of New South Wales, and Ji Xueping from the Yunnan Institute of Cultural Relics and Archaeology, report in the PLOS One that in their estimation, the bone fragment matched those from species such as Homo habilis or Homo erectus, who first stalked the planet more than 1.5 million years ago.

“Its young age suggests the possibility that primitive-looking humans could have survived until very late in our evolution, but we need to be careful as it is just one bone,” said Ji.

The 14,000 year old pre-modern thigh bone from the Red Deer Cave people. Photograph: Darren Curnoe & Ji Xueping

Curnoe said: “The new find hints at a possibility that a pre-modern species may have overlapped in time with modern humans on mainland East Asia, but the case needs to be built up slowly with more bone discoveries.”

The find comes too late for reference in a new gallery of human evolution at the Natural History Museum in South Kensington, but Chris Stringer, who heads research into human origins at the museum, greeted the find with caution. “It is an isolated bone. It is not even half a femur,” he said. “I am cautious. What we need more than anything is more complete material.”

The Natural History Museum gallery displays – either in fossil form or as casts – embrace the whole seven-million-year story of humankind’s emergence from primate ancestry, and includes a display of recent and not-so-recent finds that present human evolution as complex network of uncertain relationships and still disputed identities.

They include the “hobbit” Homo floriensis, the fragment of finger and teeth from the Denisova cave in Siberia that seem to have belonged to an unknown species, and evidence of recently identified species from South Africa (Homo naledi) and from Spain (Homo antecessor). The story of human evolution has never been straightforward, and the cast of characters keeps growing. The discoveries in the Red Deer Cave may have made the tale even more tangled.

But even the discoverers are cautious. The thigh bone from the Red Deer Cave indicates an individual who must have been small by ice age standards. He or she would have weighed about 50 kilograms. And as such finds do, it raises more questions than it can answer.

“The riddle of the Red Deer Cave people gets even more challenging now: just who were these mysterious stone age eople?” said Curnoe. “Why did they survive so late? And why only in tropical southwest China?”