Every living thing on earth contains the element carbon. When an organism dies, be it a plant or an animal, the carbon acquired during its lifetime begins to decay at a steady, predictable rate, releasing carbon-14, a radioactive isotope with a half-life of 5,730 years. By measuring the amount of carbon-14 left in the organism, scientists can estimate how long ago the organism died. Radiocarbon dates are often reported as a range.
In recent years, scientists have refined methods for radiocarbon dating. Accelerated mass spectrometry, or AMS, is more precise than standard radiocarbon dating and can be performed on smaller samples.
Radiocarbon Dating is an "ArchaeInteractive" module from North Carolina State University.