How is radiocarbon dating used

The dating process is always designed to try to extract the carbon from a sample which is most representative of the original organism.In general it is always better to date a properly identified single entity (such as a cereal grain or an identified bone) rather than a mixture of unidentified organic remains.Radiocarbon then enters animals as they consume the plants (figure 2).So even we humans are radioactive because of trace amounts of radiocarbon in our bodies.Obviously there will usually be a loss of stable carbon too but the proportion of radiocarbon to stable carbon will reduce according to the exponential decay law: R = A exp(-T/8033) where R is C ratio of the living organism and T is the amount of time that has passed since the death of the organism.By measuring the ratio, R, in a sample we can then calculate the age of the sample: T = -8033 ln(R/A) Both of these complications are dealt with by calibration of the radiocarbon dates against material of known age.

Plant eating animals (herbivores and omnivores) get their carbon by eating plants.

As explained below, the radiocarbon date tells us when the organism was alive (not when the material was used).

This fact should always be remembered when using radiocarbon dates.

All animals in the food chain, including carnivores, get their carbon indirectly from plant material, even if it is by eating animals which themselves eat plants.

The net effect of this is that all living organisms have the same radiocarbon to stable carbon ratio as the atmosphere.

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