A 14,000-year-old thigh bone suggests a mysterious prehistoric humanoid species may have lived alongside humans in southwest China.
The thigh bone is small like the primitive species Homo habilis, with a narrow shaft, and thin outer layer, but the walls of the shaft are reinforced in high-stress areas and the primary flexor muscle is very large and faces backwards, researchers said.
The Maludong humanoid likely weighed about 110 pounds, which is considered very small by pre-modern and Ice Age human standards.
“The find hints at the possibility 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,” said study co-author Darren Curnoe, of the University of New South Wales.
The team announced their Red Deer Cave discovery in 2012, sparking controversy and speculation that the bones could represent an unknown new species.
Other scientists wondered if the remains were from a very early type of modern humans, which migrated to that part of China more than 100,000 years ago.
Scientists generally believed that Neanderthals and Denisovans, the youngest pre-modern humans on mainland Eurasia, had died out about 40,000 years ago -- after anatomically modern Homo sapiens arrived.
The research team first published their findings about skull bones discovered in the cave because they believed those would be more revealing, and they found in another journal article that the skull came from a a hybrid between modern Homo sapiens and some unknown species.
They said the femur bone may have come from that unknown species.
"Their anatomy was nothing like we'd seen before in modern humans, whether they lived 200,000 or 200 years ago," said Darren Curnoe, co-author of the study. "They were truly unique and a real mystery to us and many of our colleagues."
The fossil suggests that species may have survived alongside modern Homo sapiens much later than previously believed in the biogeographically diverse region -- and researchers said the finding hints at the possibility that other pre-modern groups survived there, as well.
"If we're correct, then either there were archaic humans still around at that time in southwest China who interbred with modern humans, or their hybrid features persisted longer after interbreeding occurred because of isolation and perhaps through the action of natural selection or genetic drift," Curnoe said.
Watch this video report posted online by Slate: