Radiocarbon dating is one of the most widely used scientific dating methods in archaeology and environmental science.
Carbon dating
It can be applied to most organic materials and spans dates from a few hundred years ago right back to about 50, years ago - about when modern humans were first entering Europe. For radiocarbon dating to be possible, the material must once have been part of a living organism. This means that things like stone, metal and pottery cannot usually be directly dated by this means unless there is some organic material embedded or left as a residue. 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. 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 dating rather than a mixture of unidentified organic remains. Carbon radiocarbon formed in the upper please click for source is mostly in the form of carbon dioxide.
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This is taken up by plants through photosynthesis. Because the explained present in a plant comes from the atmosphere in this way, the ratio of radiocarbon to stable carbon in the plant is virtually the same as that in the carbon.
Plant eating animals herbivores and omnivores get their carbon by eating plants. All animals in the food chain, including carnivores, get their dating 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.
Once an organism dies the carbon is no longer replaced.
Carbon-14 dating, explained
Because the radiocarbon is radioactive, it will slowly decay away. Obviously there will usually be explained loss of stable carbon too but the proportion of radiocarbon to stable carbon will reduce according to the exponential decay law:.
The simplified approach described above does not tell the whole story. There are two reasons why the radiocarbon date is not a true calendar age:. Both of these complications are dealt with by calibration of the radiocarbon dates against material of known age. Further complications arise when the carbon in a sample has not taken a straightforward route from the atmosphere to the organism and thence to the measured sample.
Common examples are:.