All organisms contain carbon, some of which is radioactive carbon-14, an isotope that is continuously being formed in the upper atmosphere. As living organisms take up this carbon along with other carbon atoms, the ratio between the two forms remains constant. However, when they die the carbon-14 decays and is not replaced. Because it decays at a known constant rate, the decreasing concentration of carbon-14 can be measured and the date when the organism died estimated. Radiocarbon dating is one of the principal tools that archaeologists use to determine the age of the sites they investigate.
Lifeways does not perform radiocarbon dating in-house; for this purpose we use only creditable laboratories offering competitive rates. Most commonly we supply our professional partners with samples of organic materials such as charcoal or animal bone fragments from sites. Through techniques such as accelerator mass spectrometry (AMS) they provide us with the assay results to help us understand the dates. We then further refine that knowledge with other evidence in the forms of stratigraphy, artifact analyses, and studies of spatial patterning to interpret the proper meaning of those radiometric dates in specific archaeological context.