This means that dates for the final Neanderthals and for the first human occupations of Europe have been unreliable, fomenting the debate.But over the past decade, Higham and his team have developed techniques that provide more accurate readings in bones up to 55,000 years old (see Nature 485, 27–29; 2012). Since carbon is fundamental to life, occurring along with hydrogen in all organic compounds, the detection of such an isotope might form the basis for a method to establish the age of ancient materials. Libby, a Professor of Chemistry at the University of Chicago, predicted that a radioactive isotope of carbon, known as carbon-14, would be found to occur in nature.First, they use a chemical pretreatment to remove the contaminating carbon from the collagen in bones, then they measure the minuscule amounts of radiocarbon using a particle accelerator.U-series dating of bone has suffered problems of reliability since its inception because bone remains an open system with respect to uranium.Depending on the bone quality, the lab may also be able to provide % collagen yield data upon request.These analyses are also available without radiocarbon dating for a fee.
Both services use Accelerator Mass Spectrometry (AMS) technology, which gives the most advanced precision and accuracy.
During the lifetime of an organism, the amount of c14 in the tissues remains at an equilibrium since the loss (through radioactive decay) is balanced by the gain (through uptake via photosynthesis or consumption of organically fixed carbon).
However, when the organism dies, the amount of c14 declines such that the longer the time since death the lower the levels of c14 in organic tissue.
The long overlap provided plenty of time for cultural exchange and interbreeding, he adds.
Exactly what happened 30,000–50,000 years ago still vexes archaeologists because the period is right at the limit of accurate radiocarbon dating.
This discovery meant that there are three naturally occurring isotopes of carbon: Whereas carbon-12 and carbon-13 are stable isotopes, carbon-14 is unstable or radioactive.