Drs. Bonnie Blackwell and Anne Skinner will conduct a series of laboratory experiments to improve the electron spin resonance (ESR) technique and apply it to a variety of significant paleoanthropological samples. ESR provides a method to date teeth and appropriate categories of stone artifacts which date between ca. 20,000 and possibly as much as 4,000,000 years old. Because both categories of artifacts are common in archaeological sites and because many such occurrences are not datable by other available techniques, ESR, if properly developed, can provide an important anthropological tool. The technique depends on the fact that buried objects absorb small amounts of uranium from the soil and the internal as well as external bombardment by disintegration byproducts creates time dependent displacement of electrons within the sample. ESR provides a method to measure the extent to which this has occurred. When the dose rate has been determined, it is then possible to calculate age. Many prehistoric peoples heated lithics before they fashioned them into tools because the structural changes caused by heating made the material easier to work. Luckily, heat also sets the electron displacement clock to zero thus making heat treated pieces amenable to ER analysis.
While it is feasible in principle and has produced intuitively reasonable dates, ESR is not well developed and the results have been treated with understandable caution. Uranium uptake rates are hard to determine and several different models have been proposed. Blackwell and Skinner's research focuses on technique development. They shall conduct a number of experiments to: compare geochemical characteristics of enamel with associated dentine, cementum and adjacent sediments; learn how teeth absorb uranium to provide more accurate uptake models; develop a non-destructive technique which will allow hominid teeth to be dated without loss of valuable evolutionary information; compare external dose rates derived from isochron analysis with those from standard ESR measurements. They will also date samples from a series of anthropologically significant sites.
