Europe gains an edge in ax mystery

— -- Archaeologists have long been puzzled by a 1-million-year pause between when early humans started making sophisticated hand axes with two-faced blades in Africa 1.5 million years ago and when the technology finally got to Europe.

But new research is showing that advanced Stone Age tools got to Europe close to the time they reached other sites outside of Africa.

In a letter published today in Nature, two archaeologists have shown that axes from southeastern Spain are from 900,000 years ago, much older than had been believed.

That would mean it took about 600,000 years for the new ax-making technique to get to Europe.

What was surprising was that older axes hadn't been found before in Europe, says archaeologist Luis Gibert, a co-author on the letter.

The work is credible, says Rick Potts, director of the Human Origins Program at the Smithsonian Institution's National Museum of Natural History in Washington, D.C.

"If you asked me yesterday when were the earliest hand axes in Europe, I would say we have an excellent site in England called Boxgrove and that's about 500,000," he says. The new research has almost doubled that time period, from 500,000 to 900,000 years ago, Potts says.

Gibert and fellow author Gary Scott are at the Berkeley Geochronology Center, a research institute in Berkeley, Calif., that studies the history of the Earth and dating methods. They used analysis of changes in the Earth's magnetic fields to date the axes.

This dating technique works because the Earth?s magnetic polarity has flipped back and forth over the course of history. "So north would be south and south would be north," says Potts. "The last one that occurred was 780,000 years ago, and that's when north became north."

Very fine-grained magnetic materials in the rock will orient themselves with the current magnetic field, making it possible to measure which era a given area came from by dating the polarity of the Earth?s magnetic fields at the time.