The first dated materials included wood from Egyptian tombs, linen wrapping from one of the Dead Sea Scrolls, and heartwood from a California sequoia.
Radiocarbon dating is useful for dating organic materials as old as 45,000 to 50,000 years, after which little C atoms in a sample decay.
A radiocarbon date would then be an average of the range of ages of the different pieces of wood charcoal.
Likewise, standing dead trees that may be over 1,000 years old have been documented in the American Southwest and northern Mexico.
Since it decays at a known constant rate, the decreasing concentration of 14C can be measured and the date when the material died estimated.
Developed by a chemist born in Colorado, there are now commercial and academic laboratories across the globe that conduct radiocarbon dating.
Consequently, dates are expressed as radiocarbon years before present rather than as calendar years.
The type of sample can also impact the results of the date.
The best samples for the construction of calibration curves are tree rings where individual annual rings and annually laminated sediments are dated by AMS.
Ocean corals and speleothems (cave deposits such as stalactites) dated by another radiometric method—Uranium-Thorium dating—have also helped to extend the calibration curve beyond the age of the most ancient tree-ring chronologies.
As a research tool, Lifeways regularly carries out radiocarbon dating.