The dating of remains is essential in archaeology, in order to place finds in correct relation to one another, and to understand what was present in the experience of any human being at a given time and place.Inscribed objects sometimes bear an explicit date, or preserve the name of a dated individual. However, only a small number of objects are datable by inscriptions, and there are many specific problems with Egyptian chronology, so that even inscribed objects are rarely datable in absolute terms.As long as an organism lives it will take up new 14C, but from the moment it dies only decay takes place, i.e.the radioactive isotope converts to stable, ordinary nitrogen atoms 14N.These techniques both place assemblages of artefacts into relative order.Petrie used sequence dating to work back from the earliest historical phases of Egypt into pre-dynastic Neolithic times, using groups of contemporary artefacts deposited together at a single time in graves. Not all tree species are sufficiently sensitive to display distinctive variations in their ring characteristics, particularly when growing in temperate climates. Without doubt, it has made the greatest single contribution to the development of archaeology since geologists and prehistorians escaped from the constraints of historical chronology in the nineteenth century. ----- The application of tree-ring dating Unfortunately there are many problems in the direct application of dendrochronological dating. Potassium-argon (40K/40Ar) and argon-argon dating (40Ar/39Ar) 4.5.6. ----- The impact of radiocarbon dating Radiocarbon dating has grown exponentially, and many problems and inaccuracies have been isolated and examined, some leading to major adjustments of the results.
Variations in climate produced observable differences in the thickness of sediments, and, like the patterns of variation in tree rings, this allows matches to be made between deposits in separate lake beds. Palynostratigraphy Microscopic wind-blown pollen grains survive well in many soil conditions, and pollen that has accumulated in deep deposits - such as peat-bogs - can provide a long-term record of changes in vegetation; suitable samples may be collected from soils exposed by excavation, or from cores extracted from bogs. Dendrochronology It has been recognised since at least the fifteenth century that trees produce annual growth rings - their physiology was understood by the eighteenth century - and that they could be counted to calculate the age of a tree when it was felled. Key factors Click for a list of the key factors for Radiocarbon Dating 4.5.3.It must be made clear at the outset that typology is not, strictly speaking, a dating method, but a means of placing artefacts into some kind of order.Classification divides things up for the purposes of description, whereas typology seeks to identify and analyse changes that will allow artefacts to be placed into sequences.If we knew the precise length of reign for every Egyptian king, chronology would be no problem.However, we do not even know the number of kings for all periods, and there is also the possibility that reigns overlapped by coregency or in times of political disunity.When you have seen a sufficient number of cars, you can easily see that a Volkswagen Golf is more recent than a Beetle – and that the Golf looks like other cars of the same period. But this only allows us to arrange the artefacts in the correct time sequence relative to each other.To get a calendar year for an artefact, we have to use scientific methods.The rate of this decay, the half-life, is known and so by counting how many atoms decay over a particular period, it is possible to work out how much time has elapsed since the organism died.At best, the method has an uncertainty of 25 years, and due to variations in intensity of cosmic rays there are periods in the Middle Ages and more recent times when the date obtained is very uncertain. Culture history and diffusionism may - with hindsight - seem excessively preoccupied with classification and social evolution, and to have applied unsophisticated historical interpretations instead of asking fundamental questions about human behaviour. Petrie used sequence dating to work back from the earliest historical phases of Egypt into pre-dynastic Neolithic times, using groups of contemporary artefacts deposited together at a single time in graves. The extent of documentation varied considerably in 'historical' cultures and the information that survives is determined by a variety of factors. Applying historical dates to sites If a context containing burnt debris and broken artefacts is excavated on a site from a historical period, it is tempting to search the local historical framework for references to warfare or a disaster in the region, and to date the excavated context accordingly. The first half of the twentieth century witnessed similar progress that began with the dating of recent geological periods in which early hominids lived, and ended with the introduction of radiocarbon dating. Climatostratigraphy While some geologists concentrated on the age of the Earth, others studied distinctive surface traces left behind by changes in the extent of polar ice during the most recent (Quaternary) geological period. BACKGROUND It is increasingly difficult for prehistorians working in the twenty-first century to conceptualise the problems experienced by their predecessors, and approaches to interpretation before the 1960s are consistently criticised. Classification divides things up for the purposes of description, whereas typology seeks to identify and analyse changes that will allow artefacts to be placed into sequences. Sequence dating and seriation These techniques both place assemblages of artefacts into relative order. HISTORICAL DATING Prehistorians sometimes overestimate the accuracy and detail of frameworks based on historical evidence; in practice, early written sources may provide little more information than a scatter of radiocarbon dates. Geological time-scales Accurate knowledge of the age of the Earth was of little direct help to archaeologists, but it emphasised the potential of scientific dating techniques.