A newly found Stone Age people featured darker skin, an unusual mix of primitive and modern features and had a strong taste for venison.
Fossils of the so-called "Red Deer Cave People" were unearthed in southwest China and may represent a new species of human.
The fossils from two caves, date to just 14,500 to 11,500 years ago. Until now, no hominid remains younger than 100,000 years old have been found in mainland East Asia resembling any other species than our own.
"We have discovered a new population of prehistoric humans whose skulls are an unusual mosaic of primitive, modern and unique features -- like nothing we've seen before," said Darren Curnoe, associate professor in the School of Biological, Earth & Environmental Sciences at the University of New South Wales and lead author of a study about the find in the journal PLoS One.
"They have rounded brain cases with prominent brow ridges, flat but short faces with a broad nose, jutting jaws that lack a human chin, their brains are moderate in size with modern-looking frontal lobes but primitive short parietal lobes, and they have large molar teeth," added Curnoe .
Since the prehistoric humans lived in areas with a lot of sunlight and ultraviolet radiation, they were likely dark-skinned.
Ji Xueping of the Yunnan Institute of Cultural Relics and Archaeology, Curnoe and their colleagues studied the fossils, which represent the remains of at least three individuals.
For now, the mysterious humans are being called the "Red Deer Cave people," since one of the caves where they were found is Maludong (meaning Red Deer Cave) and these individuals loved that animal.
"They clearly had a taste for venison, with evidence they hunted and cooked these large deer in the cave," Curnoe explained.
These people may represent an entirely new evolutionary line on the human family tree.
"First, their skulls are anatomically unique," he said. "They look very different to all modern humans, whether alive today or in Africa 150,000 years ago. And second, the very fact they persisted until almost 11,000 years ago when we know that very modern-looking people lived at the same time immediately to the east and south suggests they must have been isolated from them."
The isolation suggests that if the Red Deer Cave people did interbreed, they did so in a limited way. The nearby modern humans at this time were the last hunter-gatherers known to this region. They had just begun to make pottery for food storage and to gather rice. Both activities mark the first steps toward full-blown farming.
It is possible that the mysterious Stone Age people might represent a very early and previously unknown migration of modern humans out of Africa. This population may not have contributed genetically to living people.
"What the discovery shows is just how complicated, how interesting, human evolutionary history was in Asia right at the end of the Ice Age," Curnoe said.
"We had multiple populations living the area, probably representing different evolutionary lines: the Red Deer Cave people on the East Asian continent, Homo floresiensis (aka the "Hobbit" human) on the island of Flores in western Indonesia, and modern humans widely dispersed from northeast Asia to Australia.
He added, "This paints an amazing picture of diversity, one we had no clue about until the last decade. It's probably the tip of the iceberg of diversity, the opening of a new chapter in recent human evolution: the East Asian chapter."
Colin Groves, a professor in the School of Archaeology & Anthropology at the Australian National University, told Discovery News that the new humans "are clearly related to Homo sapiens in general, but if they differ absolutely, then by definition they are a different species."
"In the present case, one can envisage the stem that eventually gave rise to Homo sapiens emerging from Africa and spreading over much of tropical and subtropical Asia, perhaps never very numerous or widespread, and becoming divided into several isolated or semi-isolated populations; and when Homo sapiens later spread out of Africa, these earlier sapiens-like species disappeared, being out-competed with some interbreeding with Homo sapiens," Groves continued.
The people may be linked to the Skhul/Qafzeh people out of Israel and/or the equally mysterious Denisova people from Altai, Groves said. Curnoe and his team are now attempting to recover DNA from the samples, which could answer these and other questions.