A separate species of human distinct from our own may have lived in China as recently as 11,500 years ago, scientists believe.
Fossil remains of the mysterious stone age people were discovered in two caves in south-west China in 1979 and 1989 but analysis of the finds has only now revealed their true significance.
The bones display an unusual mix of ancient and modern anatomical features, as well as some characteristics not seen before.
Scientists believe they may have belonged to a previously unknown species, distinct from that of modern humans, Homo sapiens.
However, they remain cautious about how to classify the "red deer people" - so called because they hunted extinct red deer.
Lead researcher Professor Darren Curnoe, from the University of New South Wales in Australia, said: "These new fossils might be of a previously unknown species, one that survived until the very end of the Ice Age around 11,000 years ago. Alternatively, they might represent a very early and previously unknown migration of modern humans out of Africa, a population who may not have contributed genetically to living people."
Controversy still surrounds the 2003 discovery of miniature extinct humans dubbed "hobbits" on the Indonesian island of Flores. The 3ft 6inch creatures, which may have inhabited the island as recently as 12,000 years ago, have been given their own species name, Homo floresiensis. But some experts insist they were abnormally formed modern humans.
Another puzzle emerged in 2010 with the discovery of a new human species called the Denisovans. Not only were they once widespread across Eurasia, but there is evidence that they interbred with modern humans around 50,000 years ago.
The new research, published in the online journal Public Library of Science ONE, once again places human evolution in Asia under the spotlight.
Remains of at least three "red deer people" were found at Maludong - the name means Red Deer Cave - near the city of Mengzi in Yunnan Province in 1989. They were left unstudied until research began in 2008 involving scientists from six Chinese and five Australian institutions. A Chinese geologist discovered a fourth partial skeleton in 1979 in another cave near the village of Longlin, in the neighbouring Guangxi Zhuang Autonomous Region. It remained encased in a block of rock until its removal by the international team in 2009.