Carbon dating is used to determine the age of biological artifacts up to 50,000 years old.
This technique is widely used on recent artifacts, but educators and students alike should note that this technique will not work on older fossils (like those of the dinosaurs alleged to be millions of years old).
We will deal with carbon dating first and then with the other dating methods.
Carbon has unique properties that are essential for life on Earth.
In general, academic fields such as archaeology that research material culture associated with the cultural behaviour in human history, dating artefacts is one of the foremost priorities.
To this end, the easiest way is to depend on historic records, but historical materials only provide limited information as to the scope of space and time.
Levels of carbon-14 become difficult to measure and compare after about 50,000 years (between 8 and 9 half lives; where 1% of the original carbon-14 would remain undecayed).
This rules out carbon dating for most aquatic organisms, because they often obtain at least some of their carbon from dissolved carbonate rock.
Other corrections must be made to account for the proportion of throughout the biosphere (reservoir effects).
Additional complications come from the burning of fossil fuels such as coal and oil, and from the above-ground nuclear tests done in the 1950s and 1960s.
The age of the carbon in the rock is different from that of the carbon in the air and makes carbon dating data for those organisms inaccurate under the assumptions normally used for carbon dating.
This restriction extends to animals that consume seafood in their diet.