Editor’s Note: After several years of research into a mysterious fossilized human femur, Chinese and Australian paleoanthropologists found that although the "Red Deer Cave People" who lived in Mengzi, Yunnan, China 14,000 years ago had existed up until the dawn of agricultural civilization, they retained many of the features of Homo habilis or Homo erectus. Who on earth were the "Red Deer Cave People"? Were they Homo habilis, Homo erectus or Homo sapiens? Ji Xueping, director of the development of  Paleoanthropology of the Ynan provincial Institute of Cultural Relics and Archaeology, and Darren Curnoe, professor at the University of New south wales, Australia uncover the mytery of the “Red Deer Cave People”

"Red Deer Cave People" were originally called "Mengzi People", and were first discovered in a quarry in Wenlan Town, Mengzi County, Honghe Hani and Yi Autonomous Prefecture, Yunnan. Since a number of large deer fossils were also found, archaeologists later named the site "Red Deer Cave". Ancient humans once living there were in turn named "Red Deer Cave People".

In 2012, Ji Xueping and Curnoe co-published an article in journal PLOS ONE. Based on their analysis of the skulls of the Red Deer Cave People, they concluded that although the “Red Deer Cave People” lived during the age of anatomically modern humans, they had the features of Archaic Homo sapiens that lived at least 100,000 years ago. This suggests a group of Archaic Homo sapiens had survived into the age of anatomically modern humans, spanning hundreds of thousands of years.

Ji Xueping said that the current evidence could only help make some inferences, for example, the “Red Deer Cave People” might be the last Archaic Homo sapiens or even the last Homo habilis or Homo erectus known to have existed. Another inference is that the “Red Deer Cave People” were a product of hybridization between modern humans and an ancient species. Therefore they not only retained the features of ancient humans, but also exhibited many of the behaviors of modern humans, as evidenced by the artificially drilled holes, use of pigments and manner of burial found at the site that are typical of modern humans.

"We need to find more fossil skull specimens to determine whether they were a new human species, but so far there is insufficient evidence," said Ji Xueping, "but my position has always been that the diversification of humans began a very long time ago and Homo erectus was not necessarily the only human species existing in the age of Homo erectus."

"So I can't say for sure the ‘Red Deer Cave People’ belong to Homo habilis, Homo erectus or Archaic Homo sapiens, but they can be called archaic humans," Ji Xueping said, "so it would be most accurate to say that they were the last archaic humans known to have existed."

In speaking of the greatest value of the “Red Deer Cave People”, Ji Xueping said that it had long been held that human evolution proceeded in a straight line, but now more and more evidence suggested that human evolution was a branching process and diversity had always been present in human evolution. For example, the Denisovans discovered in Siberia lived alongside anatomically modern humans and Neanderthals 30,000 years ago - the same goes for the “Red Deer Cave People” who were a branch of the human evolutionary tree.