Science / Medicine : Flaws in Carbon-14 Dating

The widely used carbon-14 method of determining the age of fossils, rocks and ancient human artifacts may be off by as much as 3,500 years, scientists said last week. Geologists from Columbia University in New York said the carbon-14 dating method appears to have significantly underestimated the age of many prehistoric objects.

The findings will probably lead to revisions of many important archeological and geological dates, such as the first cave paintings and other hallmarks of human culture, times of early human migrations and the dates of recent glacial advances. For example, the peak of the last Ice Age would shift from 18,000 to 21,000 years ago.

Carbon-14, a radioactive form of carbon, steadily decays into nitrogen. For decades, scientists have determined the age of objects dating back 10,000 to 40,000 years by looking at the ratio of carbon-14 to nitrogen.

The Columbia team used a new, highly accurate technique based on the decay of uranium into thorium to date fossilized coral found near Barbados, and then compared those dates to results of carbon-14 dating.