Rachel Wood does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.Australian National University provides funding as a member of The Conversation AU.Because atmospheric carbon 14 arises at about the same rate that the atom decays, Earth's levels of carbon 14 have remained fairly constant.Once an organism is dead, however, no new carbon is actively absorbed by its tissues, and its carbon 14 gradually decays.Isotopes of a particular element have the same number of protons in their nucleus, but different numbers of neutrons.This means that although they are very similar chemically, they have different masses.

Radiocarbon dating works by comparing the three different isotopes of carbon.

Renfrew (1973) called it 'the radiocarbon revolution' in describing its impact upon the human sciences.

Oakley (1979) suggested its development meant an almost complete re-writing of the evolution and cultural emergence of the human species.

Desmond Clark (1979) wrote that were it not for radiocarbon dating, "we would still be foundering in a sea of imprecisions sometime bred of inspired guesswork but more often of imaginative speculation" (Clark, 1979:7).

Writing of the European Upper Palaeolithic, Movius (1960) concluded that "time alone is the lens that can throw it into focus".