Variations as such are unrelated to time and natural radioactive decay.It is common practice in radiocarbon laboratories to correct radiocarbon activities for sample fractionation.
Some processes, such as photosynthesis for instance, favors one isotope over another, so after photosynthesis, the isotope C13 is depleted by 1.8% in comparison to its natural ratios in the atmosphere (Harkness, 1979).
Conversely the inorganic carbon dissolved in the oceans is generally 0.7% enriched in 13C relative to atmospheric carbon dioxide.
The ratio is measured using an ordinary mass spectrometer.
The isotopic composition of the sample being measured is expressed as δ13C which represents the parts per thousand difference (per mille) between the sample’s carbon 13 content and the content of the international PDB standard carbonate (Keith et al., 1964; Aitken, 1990).
In the case of radiocarbon dating, the half-life of carbon 14 is 5,730 years.
This half life is a relatively small number, which means that carbon 14 dating is not particularly helpful for very recent deaths and deaths more than 50,000 years ago.This nomenclature has recently been changed to VPDB (Coplen, 1994).The δ13C value for a sample can yield important information regarding the environment from which the sample comes or the mixtures of materials used to produce it because the isotope value of the sample reflects the isotopic composition of the immediate environment.Fractionation during the geochemical transfer of carbon in nature produces variation in the equilibrium distribution of the isotopes of carbon (12C, 13C and 14C).Craig (1953) first identified that certain biochemical processes alter the equilibrium between the carbon isotopes.So, the fossil is 8,680 years old, meaning the living organism died 8,680 years ago.