The high tech of prehistory

Archaeologists are finding that our love of sophisticated technology has ancient roots. The latest example is the exquisite sheen Chinese craftsmen gave to ceremonial sapphire axes about 5,000 years ago.

Peter Lu suspected there was more to that beauty than met the eye. Using modern analytical technology, he appears to have found the oldest use of industrial diamonds yet. What's more, the ancient craftsmen wielded them with skill that challenges modern technology. "It's absolutely remarkable that with the best polishing technologies available today, we couldn't achieve a surface as flat and smooth as was produced 5,000 years ago," says Mr. Lu, a graduate student at Harvard.

Whether they are taking a second look at familiar artifacts or studying a new find, archaeologists now can see deeply enough into the nature of these materials to gain insight into the technological sophistication of their makers. Chemical analyses have become so sensitive they detect the faintest presence of telltale molecules. Devices for microscopic imaging can even map out the distribution of atoms on a surface if need be.

It was assumed that the Chinese axes were polished with quartz sand, a widely used ancient abrasive. However, X-ray analysis and microscopic inspection showed the axes are 40 percent corundum. We call that mineral ruby or sapphire, depending on its color. It's the second-hardest mineral, after diamond. That's tough stuff for quartz to abrade. Microscopic comparison of the old polished surface with an area freshly polished in the lab confirmed that diamond would have been the craftsmen's best friend. Moreover, there were diamond deposits within 150 miles.

If subsequent research confirms this conclusion, Lu and the international team studying the axes will have identified the first known prehistoric use of industrial diamonds.

Another industrial technology with ancient roots is fermentation. We use it today to produce a raft of foodstuffs, including bread, cheese, and vinegar as well as beverages. Archaeochemists have pushed fermentation's antiquity back 9,000 years in the Middle East. Now an international team has found it to be just as ancient in China, but with a sophisticated twist. Instead of starting with yeast to ferment fruits and grains, the ancient Chinese started with mold. The yeast comes in later. It's a technique still used today.

By studying organic residues absorbed on pottery jars from a 9,000-year-old site in northern China, researchers found they came from a mixed fermented beverage of rice, fruit, and honey. The mold breaks down carbohydrates into fermentable sugars. This facilitates the subsequent yeast fermentation, according to Patrick McGovern at the University of Pennsylvania's Museum of Archaeology and Anthropology and his colleagues in a study published last December. Also, the many herbs added to the molds sometimes boost yeast activity up to seven-fold. It's a uniquely Chinese contribution to fermentation technology that dates from prehistoric times.

We tend to think of people back then as primitive. As archaeologists gain insight into their inventions, it is apparent that they got up to some rather sophisticated stuff.

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