From The Trenches - Dating on a Curve - Archaeology Magazine Archive

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Researchers at Queen's University Belfast recently made a big leap in sharpening the accuracy of radiocarbon dating. (Photo: Courtesy Paula Reimer)

Radiocarbon dates might seem like magic—put in a bit of ancient charcoal or bone and out comes the object's age. But it's not quite so simple. Radiocarbon dates are acquired by measuring the decay of carbon-14, an unstable isotope that living things absorb from the atmosphere. But because the amount of carbon-14 in the air has varied over the millennia, these measurements must be compared with records that can be matched to calendar dates, such as tree rings, sediment cores, or cave deposits. Scientists use these sources to build what's called a calibration curve, which greatly increases the accuracy of the dating technique.

Researchers at Queen's University Belfast in Northern Ireland have spent the last 30 years developing a new calibration curve that can accurately date archaeological finds up to 50,000 years old (the old curve, from 2004, was only good for about half of that). "This curve can help us answer important questions, from prehistoric climate conditions to how early humans evolved and adapted," says Paula Reimer of the Queen's University School of Geography, Archaeology, and Palaeoecology. Researchers have already used the new curve to correct the age of the paintings at Chauvet Cave in France, from 32,000 to 36,500 years old, using samples of charcoal from the drawings themselves. The curve has also been used to confirm the date of the earliest migration of modern humans into Europe to 45,000 years ago, earlier than previously believed.