The remains of one of the earliest modern humans to inhabit
eastern Asia have been unearthed in a cave in China.
The find could shed light on how our ancestors colonised the
East, a movement that is only poorly understood by anthropologists.
Researchers found 34 bone fragments belonging to a single
individual at the Tianyuan Cave, near Beijing.
Details of the discovery appear in Proceedings of the National
Academy of Sciences journal.
Radiocarbon dates, obtained directly from the bones, show the
person lived between 42,000 and 39,000 years ago.
"For this time period, which is critical for understanding the
spread of modern humans around the world, we have two well-dated
human fossils from eastern Asia," said co-author Professor Erik
Trinkaus, from Washington University in St Louis, USA.
"We have remains from the Niah Cave from Sarawak on Borneo, and
now this specimen from China. As you go west, the next specimens are
from Lebanon. There's nothing in between."
According to the "Out of Africa" theory, modern humans (Homo
sapiens) evolved in East Africa and then spread out across the
globe about 70,000 years ago, replacing earlier, or archaic, human
populations, such as the Neanderthals [in the west or Homo
erectus in the east], with very little, if any, interbreeding.
The Tianyuan remains display diagnostic features of modern H.
sapiens. But co-author Erik Trinkaus and his colleagues argue,
controversially, that the bones also display features characteristic
of earlier human species, such as relatively large front teeth.
The most likely explanation, they argue, is interbreeding
between early modern humans emerging from Africa and the archaic
populations they encountered in Europe and Asia.
"The pattern we see across the Old World is basically a modern
human in terms of its newly emerged characteristics, but also a
minority of traits that are absent or lost in the earliest modern
humans in East Africa," Professor Trinkaus said.
"The question is where did they get them from? Either they
re-evolved them, which is not very likely, or, to some degree, they
interbred with archaic groups.
"Sex happens. I find this neither disturbing nor surprising."
He added that evidence from the animal world suggested two
closely related species, which have been separate for less than two
million years, could interbreed successfully when given the
opportunity to mate.
One example from the UK is the Scottish wildcat, which is being
absorbed into domestic cat populations through interbreeding.
The domestic cat and the wildcat are distinct species separated
by hundreds of thousands, if not millions, of years, and have very
different body sizes. Despite this, pairings produce fertile, viable
Signs of disease
The view of interbreeding between Homo sapiens and
archaic humans is controversial. Other palaeoanthropologists say
that some of these features are simply retained from ancient African
And most genetic evidence gathered from present-day humans does
not appear to support significant interbreeding between modern
humans from Africa and archaics.
The researchers' analysis of the bones has revealed several
interesting details about the Tianyuan individual's lifestyle.
The person's age at death was estimated by how much the teeth
had worn down. This put them in their late 40s or 50s.
But the lack of a pelvis among the remains means that it is not
possible to say with any certainty what sex the individual was.
The Tianyuan specimen shows several signs of disease. The
individual had lost a number of their teeth before death, not
unusual considering their age.
The researchers also identified several lesions, or growths, on
the leg bones, which appear to have been caused by a condition
affecting the muscle attachments around both knees.
Whatever condition these were caused by, however, it does not
appear to have disabled the person, because the remainder of the leg
bones suggest the person kept active.
The single toe bone which was unearthed seems to suggest the
individual wore shoes, pushing back the earliest known evidence for
footwear by about 10,000 years.
An earlier study by Professor Trinkaus shows that human small
toes became weaker during the stage of prehistory known as the Upper
Palaeolithic, and that this can probably be attributed to the
adoption of sturdy shoes.
The invention of rugged shoes reduced humans' reliance on
strong, flexile toes to grip and balance.