The fossilized remains of stone age people recovered from two caves in south west China may belong to a new species of human that survived until around the dawn of agriculture.
The
partial skulls and other bone fragments, which are from at least four
individuals and are between 14,300 and 11,500 years old, have an
extraordinary mix of primitive and modern anatomical features that
stunned the researchers who found them.
Named the Red Deer Cave
people, after their apparent penchant for home-cooked venison, they are
the most recent human remains found anywhere in the world that do not
closely resemble modern humans.
The individuals differ from modern
humans in their jutting jaws, large molar teeth, prominent brows, thick
skulls, flat faces and broad noses. Their brains were of average size
by ice age standards.
"They could be a new evolutionary line or a
previously unknown modern human population that arrived early from
Africa and failed to contribute genetically to living east Asians," said
Darren Curnoe, who led the research team at the University of New South Wales in Australia.
"While
finely balanced, I think the evidence is slightly weighted towards the
Red Deer Cave people representing a new evolutionary line. First, their
skulls are anatomically unique. They look very different to all modern
humans, whether alive today or in Africa 150,000 years ago," Curnoe told
the Guardian.
"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. We might infer from this isolation that they
either didn't interbreed or did so in a limited way."
One partial
skeleton, with much of the skull and teeth, and some rib and limb bones,
was recovered from Longlin cave in Guangxi province. More than 30
bones, including at least three partial skulls, two lower jaws and some
teeth, ribs and limb fragments, were unearthed at nearby Maludong, or
Red Deer Cave, near the city of Mengzi in Yunnan province.
At
Maludong, fossil hunters also found remnants of various mammals, all of
them species still around today, except for giant red deer, the remains
of which were found in abundance. "They clearly had a taste for venison,
with evidence they cooked these large deer in the cave," Curnoe said.
The findings are reported in the journal PLoS ONE.
The
stone age bones are particularly important because scientists have few
human fossils from Asia that are well described and reliably dated,
making the story of the peopling of Asia hopelessly vague. The latest
findings point to a far more complex picture of human evolution than was previously thought.
"The
discovery of the Red Deer Cave people shows just how complicated and
interesting human evolutionary history was in Asia right at the end of
the ice age. We had multiple populations living in the area, probably
representing different evolutionary lines: the Red Deer Cave people on
the East Asian continent,
Homo floresiensis, or the 'Hobbit',
on the island of Flores in Indonesia, and modern humans widely dispersed
from northeast Asia to Australia. This paints an amazing picture of
diversity, one we had no clue about until this last decade," Curnoe
said.
Much of Asia was also occupied by Neanderthals and another
group of archaic humans called the Denisovans. Scientists learned of the
Denisovans after recovering a
fossilized little finger from the Denisova cave in the Altai mountains of southern Siberia in 2010.
The
fossils from Longlin cave were found in 1979 by a geologist prospecting
in the area. At the time, researchers removed only the lower jaw and a
few fragments of rib and limb bones from the cave wall. The rest of the
skeleton was left encased in a block of rock, which sat in the basement
of the Yunnan Institute of Cultural Relics and Archaeology in Kunming,
Yunnan, for 30 years. The fossils were rediscovered in 2009 by
Ji Xueping, a researcher at the institute, who teamed up with Curnoe to examine the remains.
"It
was clear from what we could see that the remains were very primitive
and likely to be scientifically important. We had a skilled technician
remove the bones from the rock, and they were glued back together. Only
then was it clear what we had found: a partial skeleton with a very
unusual anatomy," Curnoe said.
The fossils at Maludong were found in 1989 but went unstudied until 2008.
Lumps
of charcoal uncovered alongside the Longlin fossils were carbon dated
to 11,500 years, a time when modern humans in southern China began to
make pottery for food storage and to gather wild rice in some of the
first steps towards full-scale farming.
Marta Mirazón Lahr,
an evolutionary biologist at Cambridge University, is convinced the
remains are from modern humans. The unusual features, she said, suggest
the Red Deer Cave people are either "late descendants of an early
population of modern humans in Asia" or a very small population that
developed the traits through a process known as
genetic drift.
Chris Stringer, head of human origins at the Natural History Museum, London, was similarly sceptical.
"The
human remains from the Longlin Cave and Maludong are very important,
particularly because we do not have much well-described and well-dated
material from the late Pleistocene of China.
"The fossils are
unlike recent populations of modern humans in several respects, and the
mosaic of more archaic features could indicate the dispersal of a poorly
known and more primitive form of modern human that left Africa before
the main exodus at about 60,000 years. This dispersal could have reached
as far as China, surviving there for many millennia, before
disappearing in the last 12,000 years."
But he added: "There might
be another possible explanation for the more archaic features. Could
these alternatively be attributed to gene flow from a more archaic
population that survived alongside modern humans? In the case of the
Longlin Cave and Maludong fossils, the most likely candidate would be
the enigmatic Denisovans who apparently interbred with the ancestors of
modern Australasians somewhere in south east Asia. Could these Chinese
fossils be further evidence of such hybridization?"
