Modern humans took over Europe in just 5,000 years

From: Janice Matchett <janmatch@earthlink.net>
Date: Thu Feb 23 2006 - 09:50:27 EST

Item of interest in light of recent discussion. ~ Janice

Modern humans took over Europe in just 5,000 years
www.nature.com/news ^ | 22 February 2006 | Michael Hopkin
http://www.nature.com/news/2006/060220/full/060220-11.html

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Better bone dates reveal bad news for
Neanderthals Modern humans took over Europe in
just 5,000 years. Michael Hopkin

These drawings from the Chauvet cave were
originally dated to around 31,000 years ago. But
a new analysis pushes that back four or five thousand years.

Nature, with permission from the French
Ministry of Culture and Communication.

Advances in the science of radiocarbon dating - a
common, but oft-maligned palaeontological tool -
have narrowed down the overlap between Europe's
earliest modern humans and the Neanderthals that preceded them.

Refinements to the technique, which estimates an
artefact's age by sampling the amount of
radioactive carbon left over from when it was
formed, suggest that Homo sapiens wrested Europe
from its prehistoric counterpart even quicker than had been thought.

Previous estimates suggested that at least 7,000
years elapsed between H. sapiens arriving in
eastern Europe more than 40,000 years ago, and
the disappearance of the last known Neanderthals
(H. neanderthalensis) from western France. But
newly calculated dates shrink the overlap to 5,000 years.

Radiocarbon dating, also known as carbon dating,
is a reliable method for dating artefacts back to
around 23,000 years ago. But for items older than
this it has tended to underestimate ages by up to several thousand years.

Carbon dating is based on the rate of decay of
radioactive carbon-14 atoms found in living
matter such as bones. Because carbon-14 decays to
a non-radioactive form over time, older samples give off less radiation.

But carbon-14's half-life is 5,730 years. So any
sample older than about 30,000 years will have
only 3% of its original carbon-14. For such
samples, even tiny amounts of contamination can
yield wildly inaccurate results.

If you'd have talked to me two years ago I would
have said that radiocarbon dating was a dead loss.

Paul Mellars, University of Cambridge

What's more, the method originally assumed that
levels of carbon-14 in the environment have
remained constant, meaning that all samples had
the same initial level of radioactivity. But this is not true.

Giant hurdle

Palaeontologists studying the colonization of
Europe had feared that these complications were
insurmountable, and that samples of the vintage
in which they were interested could not be dated with confidence.

"Two years ago I would have said that radiocarbon
dating in that period was a dead loss," says
archaeologist Paul Mellars of the University of
Cambridge. "We were all in despair - I thought
I'd have to just go off and become a bus driver, or something."

Now, however, as Mellars describes in this week's
Nature1, two key advances have put carbon dating
back on the map. By 'ultrafiltering' bone samples
to get rid of smaller molecules and retain only
the larger ones, researchers can prepare far
purer samples. And recent analysis of sea
sediments from the Cariaco Basin near Venezuela
have provided the most accurate record yet of how
environmental carbon-14 levels have fluctuated,
allowing the technique to be calibrated back to around 50,000 years.

Swift conquest

All this means that modern humans' displacement
of the Neanderthals was probably swifter than
previously thought. Previous dating had suggested
that H. sapiens arrived in Europe 43,000 years
ago, and covered the continent by 36,000 years
ago. But the refined figures are 46,000 and
41,000 years, says Mellars - just 5,000 years to colonize an entire continent.

Neanderthals are not expected to have lasted long
in the face of such an influx. "Modern humans had
better weapons, more complicated language, and
were better organized," Mellars says. "Once they
arrived, Neanderthals didn't survive for long."

He suspects that our bulky cousins, despite being
well adapted to cold, were killed off by a
"double whammy" of competition with humans and a
climatic cold snap that occurred at around the
same time. "I would be surprised if the two
species coexisted in any one place for more than
around 1,000 years," Mellars says.
Received on Thu Feb 23 09:51:05 2006

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