Dregs in jar tell of ancient wine-making.

The concept of a "vintage year" took on new meaning this week when scientists presented the first chemical evidence that wine existed as far back as about 3500 B.C.

Wince residues in clay jars and a wine-marking apparatus document that people produced the fermented beverage almost half a millennium earlier than experts thought, says Patrick E. McGovern, an archaeological chemist with the University of Pennsylvania in Philadelphia. He and Virginia B. Badler, a University of Toronto graduate student, announced their findings at a symposium on the ancient history of wine, held in California's Napa Valley.

Badler had noticed a red stain while piecing together jars excavated from an Iranian site called Godin Tepe, an outpost built along what later became a major Middle Eastern trade route. The 7-and 14-gallon containers had long, narrow necks and a body shape that suggested they once stored liquids while resting on their sides, just as wine is stored today. Other finds at the site included stoppers for the jars and a funnel with a heavy lid that could have been used to press grapes.

At first, Badler and McGovern didn't know what to make of the stain. "It was just a colored deposit," McGovern recalls. But the jars' shape and the associated equipment made them suspicious, so they compared the stain with a similar stain in an ancient Egyptian vessel known to have contained wine. The researchers scraped the reddish residue from the jars and analyzed the samples with infrared spectroscopy, which distinguishes chemical components by the wavelengths of light they absorb.

Residues from the Iranian and Egyptian jars looked alike and were full of tartaric acid, a chemical naturally abundant only in grapes. "Those crystals are a signature for wine," says anthropologist Solomon H. Katz of the University of Pennsylvania.

More than two dozen archaeologists and other researchers showed up this week at the Robert Mondavi Winery in Oakdale, Calif., to discuss their work. Some came with samples in hand, including an unopened bottle of Roman wine found on a sunken ship. Now that the Iranian discoveries have pushed back the beverage's origins, says McGovern, "we're trying to get people to look more carefully at their collections for potential wine vessels."