The Oxford Companion to Archaeology defines radiocarbon dating as “an isotopic or nuclear decay method of inferring age for organic materials." This method works roughly as follows. Carbon 14 is a radioactive isotope of carbon 12. All plants and living creatures contain carbon 14 while they are alive. When a living thing dies, it begins to lose the carbon 14 at a steady rate: approximately half the carbon 14 is lost every 5730 years (the “half-life" of radiocarbon). Therefore, if archaeologists find a piece of charcoal in an excavation, by measuring the amount of carbon 14, a lab can determine roughly when the tree from which the charcoal came was chopped down. A type of radiocarbon dating called accelerator mass spectrometry (AMS) can be used for dating smaller samples of organic matter. Because wood was valuable in Palestine's arid environment and therefore sometimes was in use for long periods or recycled, it yields less precise dates than grain and seeds (in other words, a piece of wood could have been used or reused as a ceiling beam for decades and even centuries before it was burnt).
Radiocarbon dating has the advantage of being the only “scientific" method listed here (meaning that the date is supplied by a laboratory). However, it has the disadvantage that every date returned by the lab has a plus/minus range, representing a margin of statistical error. There is a 67 percent chance that the date provided by the lab falls within the plus/minus range. A date of 4000 plus/minus 100 would mean that our tree was chopped down 4000 years ago, with a 67 percent chance that it was chopped down within a range of 100 years either way (the accuracy goes up if the range is doubled). Radiocarbon dates conventionally are published in the form of uncalibrated radiocarbon years before present (BP), with “present" measured from 1950 C. E., when the method was invented. Conversion of these dates to calendar years requires calibration because of past fluctuations in the level of carbon 14 in the atmosphere. Calibration can increase the range of a radiocarbon date.
For these reasons, radiocarbon dating is most useful in cases in which there are no other closely datable types of artifacts, such as prehistoric sites in Europe or Native American sites in the United States. It is less useful for historical period sites in Palestine, where other, more accurate methods of dating are available. Nevertheless, radiocarbon dating is valuable even in Palestine, as indicated by its centrality in the ongoing debate about the kingdom of David and Solomon (the key question being whether certain archaeological remains are associated with these kings or are later in date). Another disadvantage of radiocarbon dating is that it can be used only on organic materials, which are exactly the kinds of remains that are rarely preserved at ancient sites. Organic materials such as wooden furniture, rugs, woven mats and baskets, clothing, leather, and scrolls may survive in extremely arid conditions such as the area around the Dead Sea, but for the most part have disintegrated in other parts of Palestine as a result of humidity.
There are other scientific methods of dating such as dendrochonology (treering dating), but they are rarely employed for the historical periods in Palestine.
World History
