====== Scientific Methods ======

===== Radiocarbon dating =====

==== Introduction ====


**Radiocarbon (<sup>14</sup>C) dating** introduced by Arnold and Libby (1949) was one of the most significant leaps in the history of archaeology, history and the history of art. This technique allows scientists to estimate the absolute date of death of any organism. Using the isotopic ratios of the radioactive carbon-14 and stable carbon-12 in the organism’s tissues and comparing it to the ratio in Earth’s atmosphere permits to calculate how long it was since the organism stopped exchanging carbon with its surrounding. Further developments in the field included the introduction of the **calibration process** in order to account for the fluctuations of the <sup>14</sup>C/<sup>12</sup>C ratio in the atmosphere through time, and the use of **mass spectrometry (MS)** to arrive at more precise measurements using smaller samples (Bayliss 2009). The most recent important addition to the <sup>14</sup>C dating methodology is the use of **Bayesian modelling** (Bronk Ramsey 2009) - a series of statistical tools which help to incorporate additional information (e.g. archaeological, historical, textual) into the absolute chronology, effectively reducing the errors of the radiocarbon dates.

==== Radiocarbon dating of Mesopotamian materials ====

For more than a century now, chronologies of the Mesopotamian civilisations were devised using primarily historical (written accounts) and archaeological methods (development of material culture). Although the need for the inclusion of scientific methods into the construction of absolute chronologies was recognised decades ago (Mellaart 1979; Bruins & Mook 1989), relatively few improvements in this direction have been made. Radiocarbon dating of Mesopotamian material is problematic for a number of reasons:

  * The **availability** of radiocarbon dating samples has been a long-standing issue in the study of Mesopotamian chronology. Most of the available material came from excavations conducted during the late 19<sup>th</sup> and early 20<sup>th</sup> century. Due to social and political instabilities in the region, few new excavations were conducted.
  * Radiocarbon measurements can only be seen as reliable sources of chronological informations if they were conducted on material from properly excavated and documented **archaeological contexts**. Information about these is often lacking, especially in the case of important Mesopotamian sites (Ur, Kish, Uruk, etc.).
  * The nature of the **material** has significant impact on the reliability of the radiocarbon date. **Short-lived** plants and textiles (twigs, textiles etc.) and bones are more likely to produce precise and accurate absolute dates than long-lived materials (e.g. shells, wood) or charcoal.
  * **Plateaus in the calibration curve**, i.e. periods of increased production of <sup>14</sup>C in the Earth’s atmosphere, can cause the errors of the radiocarbon dates to increase drastically, obscuring the absolute chronology. One such period occurred during the Early Dynastic era, between ca. 2820-2580 BC (Reimer et al. 2012). This problem can only be alleviated with the production of new radiocarbon dates.

[[14C Dates from Mesopotamia]]

===== Dendrochronology =====

===== Thermoluminescence =====

===== Bibliography =====
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