Jinmium rock shelter is famous for the claims made by Fullugar et al. (19%) for the early human colonization and ancient rock art of northern Australia. These claims were based on thermoluminescence ages obtained for the artefact-bearing quartz sediments that form the JIoor deposit at the site. In this paper, we outline the background to the optical dating programme at Jinmiurn, and describe the experimental design and statistical methods used to obtain optical ages from single grains of quartz sand. The results, interpretations, and implications of this dating programme are reported in a companion paper (Roberts et al. 1999, this volume).

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The expansion of modern human populations in Africa 80,000 to 60,000 years ago and their initial exodus out of Africa have been tentatively linked to two phases of technological and behavioral innovation within the Middle Stone Age of southern Africa—the Still Bay and Howieson's Poort industries—that are associated with early evidence for symbols and personal ornaments. Establishing the correct sequence of events, however, has been hampered by inadequate chronologies. We report ages for nine sites from varied climatic and ecological zones across southern Africa that show that both industries were short-lived (5000 years or less), separated by about 7000 years, and coeval with genetic estimates of population expansion and exit times. Comparison with climatic records shows that these bursts of innovative behavior cannot be explained by environmental factors alone.

To display a number of estimates of a parameter obtained from different studies it is common practice to plot a sequence of confidence intervals. This can be useful but is often unsatisfactory. An alternative display is suggested which represents intervals as points on a bivariate graph, and which has advantages. When the data are estimates of odds ratios from studies with a binary response, it is argued that for either type of plot, a log scale should be used rather than a linear scale.

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