Big Freeze Didn't Kill Off Neandertals, Study Says

September 12, 2007

Climate change might have had a hand in the demise of the Neandertals, but it wasn't the main culprit, a new study says.

The research is the latest contribution to a longstanding debate as to what finally did in the ancient human species some 30,000 years ago.

Some scientists blame the sudden onset of ice age conditions in Europe and western Asia, while others link the extinction to the arrival of modern humans from Africa.

Now a team led by Polychronis Tzedakis of the University of Leeds in England says it has detected no extreme climate shifts during the time the Neandertals (often spelled "Neanderthals") disappeared.

"We can eliminate catastrophic climate change as a factor in the Neandertal extinction," Tzedakis said.

Carbon Clues

The research, reported this week in the journal Nature, focused on finds from Iberia (modern-day Spain and Portugal)—the region identified as the Neandertals' last European stronghold.

Recently analyzed remains from Gorham's Cave in the British territory of Gibraltar suggest that the Neandertals died out there sometime between 30,000 years ago—in line with previous estimates—and 24,000 years ago. (See a Gibraltar map.)

So Tzedakis' team compared the radiocarbon dates of pinecone scales and charcoal recovered from the Neandertal cave to prehistoric climate records.

The scientists used a new method in the comparison, because radiocarbon years don't necessarily match up with calendar years.

Radiocarbon dates are calculated by measuring the radioactivity of the carbon found in all living things. Radiocarbon, or radioactive carbon, is continually being added in small amounts during life but decays at a fixed rate after death.

This carbon ultimately comes from the air, and varying levels of radiocarbon in the atmosphere "can cause the clock either to race forward or stand still," Tzedakis said.

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