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Moreover, the presence of charcoal in the vicinity of stone tools offers no proof that it is of anthropic origin, especially in a region that is prone to natural fires.These very brief comments should merely convey an inkling of the true complexity of dating issues, more details relating to carbon isotope analysis are given below.This is now thought to be about 5733 years for radiocarbon, but we continue to use Libby’s original estimate of 5568 years, for consistency. The assumption that the ratio of carbon isotopes in the carbon reservoir of the Earth are the result of a complete and rapid equalisation is not necessarily valid. The assumption that the ratios of carbon isotopes are only altered by radioactive decay is only approximately valid. The levels of radiocarbon cannot be measured with real accuracy.These issues are too complex to be examined in any detail here.As a noun, ‘date’ may refer to the date shown on a coin, book or building, presumably representing the time of minting, printing or completion, i.e. But it may alternatively refer to a time period of some considerable duration (e.g.hundreds of millennia) from which an archaeological, palaeontological or geological phenomenon supposedly ‘dates’.All radiometric techniques (as well as some non-radiometric dating methods, such as fission-track analysis) provide sets of statistical information thought to relate to the age of samples; they do not yield sidereal or calendar ages.The probability statements they offer can be expressed at one, two or more standard deviations, which means that the true age of the sample would be within stated tolerance values if all secondary qualifications were ignored.
In nearly all cases, such data are subject to significant qualifications, which in archaeological use are not adequately taken into account.In the case of radiocarbon, the remnant content of an unstable and thus radioactive isotope of carbon is determined to estimate the time when its decay to nitrogen commenced.For this to be accurate it is necessary to know the initial concentration of carbon-12, 13 and 14; the decay rate; and that the process had not been influenced by other factors. The initial atmospheric concentrations of 14C and d13C are not known to us.Moreover, due to its extremely low specific gravity relative to other sediment particles, charcoal tends to ‘float’ on top of a deposit through trampling or other disturbances, and it is easily transported by wind, water and biological agents (e.g. Its taphonomy ensures that few charcoal pieces are recovered from the locations of actual hearths, so there is no proof that they provide precise dates for the final deposition of the sediment they were recovered from (Bednarik 1989a).Even when the charcoal is extracted from a well-defined hearth, there is the possibility that charcoal or wood of various ages has been used.
They are well understood by radiocarbon scientists, but are not often reflected in the pronouncements of archaeologists about such results, as the excessive confidence in them indicates.