Carbon dating, a valuable tool for placing ancient archaeological finds in context, is now being applied to date more modern treasures: pricey bottles of scotch.

Researchers at the Oxford Radiocarbon Accelerator Unit (ORAU) in England have applied their craft to sniff out counterfeit whiskeys, with the help of an unsavory ally: 20th-century nuclear tests. Those tests left their mark in the isotope record, significantly boosting levels of atmospheric carbon 14, the radioactive form of the element that researchers measure in carbon dating. Living things take up carbon from the environment, so barley grown during the nuclear era—and the whiskey distilled from it—bears an increased load of carbon 14. (Carbon dating of truly ancient objects uses the steady decay of carbon 14 in once-living tissues as a marker of age: the older something is, the less carbon 14 it has left.)

Stakes are high in the antique whiskey business—a bottle of 1926 Macallan fetched $54,000 at Christie's New York in 2007—and forgeries appear to be commonplace. "So far there have probably been more fakes among the samples we've tested than real examples of old whisky," Tom Higham, deputy director of the ORAU, told PlanetEarth online. Among those bogus bottles, reportedly: a Macallan supposedly from 1856 that tests showed to have originated post-1950, when aboveground nuclear tests began upping levels of carbon 14 worldwide.

"It is easy to tell if whisky is fake," Higham told the U.K.'s Telegraph newspaper, "as if it has been produced since the middle of the twentieth century, it has a very distinctive signature." Earlier samples can be tougher to nail down precisely: "If it's from before [1950] we may only be able to say that it doesn't contain bomb carbon," Higham told PlanetEarth online.

Levels of carbon 14 from nuclear explosions peaked in the mid-1960s, when test ban treaties began to take hold. Enterprising scientists have already used the nuclear record to trace the regeneration of human cells, last month establishing that human heart cells do in fact regrow over a person's lifetime.

For more on nuclear testing, see our coverage of proliferation and test bans, France's plan to compensate those harmed by its tests, and this feature from the March issue on detecting covert nuclear tests.

Photo of whiskey barrels in Scotland: foxypar4 on Flickr