Teeth dating

Plenary 79. FI G M Edwards, e-mail address h.g.m.edwards bradford.ac.uk (NIR-FTRS). A review of recent applications of RS to archeology—characterizing ancient pigments, human skin, bone, ivories, teeth, resins, waxes and gums. Aging effects and dating possibilities. Emphasizes use of microscopic Raman. 

Bones and teeth, however, are primary archaeological materials and are common to many archaeological sites. Bones bearing cut marks from stone tools are a clear proxy for human occupation of a site, and in the study of human evolution, hominid remains provide the primary archive material. Hence, many attempts have been made to directly date bones and teeth using the U-series method. Unlike calcite, however, bones and teeth are open systems. Living bone, for example, contains a few parts per billion (ppb) of Uranium, but archaeological bone may contain 1-100 parts per million (ppm) of Uranium, taken up from the burial environment. Implicit in the calculation of a date from °Th/U or Pa/ U is a model for this Uranium uptake, and the reliability of a U-series date is dependent on the validity of this uptake model. 

An alternative to the early uptake assumption, linear uptake, assumes that bones and teeth continue to take up Uranium at a constant rate (Ikeya 1982 Bischoff et al. 1995), giving a U-series date something over twice that calculated using the EU assumption. Although more common for teeth than for bone, both EU and LU dates are often quoted for the same sample, with the implication that the true age of the sample probably lies somewhere in between. 

EU and LU are not the only uptake models that have been proposed. More mathematically sophisticated models have been developed (e.g., Szabo and Rosholt 1969 Hille 1979 Chen and Yuan 1988), in some cases using both the U and U decay chains (see Ivanovich 1982 Millard and Pike 1999 for summaries). While there have been some apparently successful applications of these models, none have been found to be universally applicable, and the search for a reliable method of U-series dating of bones and teeth continues. In the last decade or so, two important new approaches to the modeling of U uptake in bones and in teeth have been developed. These are discussed in detail below. 

There are a few developments on the horizon that will increase our ability to date bones and teeth reliability. Both y- and a-spectrometric methods can measure Pa/ U and °Th/U and concordance between dates calculated using the two can provide a measure of reliability. However, the discordance between the two is not very sensitive to different uptake regimes, and it is difficult to resolve, for example, bones that have undergone EU from those that have undergone LU with the analytical errors commonly encountered in measurements by y- and a-spectrometry. On the other hand, it has been shown recently that TIMS can measure both isotopic ratios with a precision usually better than 1% (Edwards et al. 1997). TIMS measurements of Pa/ U and °Th/U have yet to be routinely applied to dating fossil remains, but in the future, concordance between the two decay series will provide further evidence of the validity of a particular uptake model to a particular sample. 

McDermott et al. (1993) produced EU U-series dates and both EU and LU ESR dates on teeth from the hominid bearing layers of Tabun, Qafzeh and Skhul. Their results suggest both the Neanderthals and Modem Humans from Tabun, Skhul and Qafzeh are much older that previously thought, at around 100 5 ky. Some faunal dates from Skhul were younger at around 43 ky, but were possibly the result of recent accumulation of uranium. Not only do these dates represent some of the earliest modem human skeletal material found anywhere, but the dates of the Neanderthal layers were broadly... 

In 1988, Chen and Yuan published U-series dates on bones and teeth for more than 20 Chinese sites, providing the first extensive Palaeolithic chronology for China. They used a-spectrometric measurements of °Th/U, and and used concordance... 

Chen T, Yang Q, Wn E (1992) ESR dating of teeth enamel samples from Jiimiushan palaeoanthropological site. Acta Anthro Sinica 12 337-346... 

Chen T, Ynan S (1988) Uraninm-series dating of bones and teeth from Chinese Paleohthic sites. Archaeometry 30 59-76... 

Griin R, Stringer CB, Schwarcz HP (1991) ESR dating of teeth from Garrod s Tabun cave collection. J Human Evol 20 231-248... 

Pike AWG, Hedges REM (2001) Sample geometry and U-uptake in archaeological teeth implications for U-series and ESR dating. Quat Sci Rev 20 1021-1025... 

The supposed human remains were accompanied by flint implements and animal teeth, all of which apparently supported the early date attributed to the find. The flint implements were of a reddish color, matching that of local flints, but spectrographic analysis revealed that they had been artificially stained with chromium and iron salts below the layer of stain there was a white crust, whereas local flints were brown throughout. The animal teeth also seemed to have been "planted" at the burial site so as to suggest an early date the red-brown color of the teeth had also been artificially stained chromium and iron had been found when they were analyzed. A hippopotamus tooth, previously supposed to be contemporary with the tool carved from the elephant s tusk, was also stained with chromium and iron salts and contained little fluorine. 

Amino Acid Dating Techniques depend on the "rates of hydrolysis reactions of proteins and racemization, epimerization, and decomposition reactions of amino acids [they have] been applied to the age-dating of fossil bone, teeth, and shell. Activation energies range from near 20 kcal per mole for hydrolysis reactions to around 30 kcal per mole for racemization... 

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