As years passed and more tests were made (soon by laboratories counted in scores), a rather consistent deviation between radiocarbon age and historical age started to receive the attention of researchers.The radiocarbon dates diverge from the historical dates by several hundred years (often 500 to 700), and, interestingly, in the Egyptian samples more so than in samples from most other ancient civilizations.Folghereiter done at the turn of the century on Attic and Etruscan pottery: he found that the polarity was reversed in the eighth century before the present, era.To determine the extent of correction necessary to render the radiocarbon method reliable, dendrochronologists devised a plan to control the radiocarbon dates by building a chronology of tree rings of the white bristlecone pine, the longest living tree.
Both of these contaminates, natural and artificial, will make the bones carbon dating much younger than it actually is.
Items such as limestone and plant roots can be considered naturally occurring contaminates because they will introduce new radiocarbon on the bones.
An example of artificial contaminates are paper and animal glue in labeling a bone.
In addition, carbon dating by the use of half lives could be utilized.
However, the problem that comes here is that in an arid climate some types of trees will die but will hold their position.