New ages for the post-Howiesons Poort,late and final Middle Stone Age at Sibudu,South Africa

Optically stimulated luminescence (OSL) measurements are reported for single grains of quartz from deposits within Sibudu rock shelter. Such measurements enable rejection of unrepresentative grains and application of the finite mixture and central age models to obtain the most reliable age estimates. Three types of single-grain equivalent dose (D_e) distributions were observed: one sample represented a single dose population, three samples indicated mixing between Iron Age (IA) and Middle Stone Age (MSA) deposits, and 10 samples (in addition to the three mixed samples) showed scattered distributions. The latter type resulted from differences in the beta dose received by individual grains. For these samples, the beta doses were modelled and adjusted accordingly. Ages for the 14 samples collected from MSA deposits post-dating the Howiesons Poort (HP) resulted in three age clusters, which are stratigraphically consistent with the three informally named cultural phases at Sibudu: namely, the post-HP, late MSA and final MSA. Weighted mean ages of 58.5 ± 1.4 ka, 47.7 ± 1.4 ka and 38.6 ± 1.9 ka were calculated for these phases, respectively. The three phases were separated by two occupational hiatuses with durations of 10.8 ± 1.3 ka and 9.1 ± 3.6 ka. We hypothesise that the punctuated presence of humans at Sibudu was determined by large-scale fluctuations in climate during oxygen isotope stage (OIS) 3, which resulted in alternating wet and dry periods. Phases of occupation correspond to wet periods when fresh water was available in the Tongati River, whereas intervals of site abandonment correspond to dry periods when people were forced to migrate in search of a reliable source of fresh water. Where people migrated to, remains unresolved.     

The potential of bird remains for environmental reconstruction

Until relatively recently, studies of bird remains have been regarded as peripheral to mainstream research on early archaeological and palaeontological sites, rather than a potentially crucial factor in the reconstruction of the past environments in which hominids and other larger mammals were present This paper sets out to define the range of ecological information for a site which can be gained through study of the bird bones, using as an example the bones recovered in the excavations at Gorham's Cave, Gibraltar. © 1997 John Wiley & Sons, Ltd.     

Cross-platform program for likelihood-based statistical comparisons of mortality profiles on a triangular graph

The construction of mortality profiles to investigate age-at-death patterns is a typical component of most faunal analyses. While many methods exist for constructing and comparing mortality profiles, plotting the percentages of juvenile, prime, and old individuals on a triangular graph, or ternary diagram, remains a popular method for making comparisons. Typically, these comparisons are made visually, but because sample sizes are often small, any differences may be the product of sampling rather than meaningful contrasts in depositional history. To overcome this problem, here we present a likelihood-based method for making statistical comparisons of mortality profiles on a triangular graph, and we make available a cross-platform computer program that implements the method. Although we developed the method with mortality profiles in mind, in principle, it can be used to analyze any kind of artifact for which there are three distinct categories.     

Correcting temporal frequency distributions for taphonomic bias

In this paper, we expand upon a prior study [Surovell, T.A., Brantingham, P.J., 2007. A note on the use of temporal frequency distributions in studies of prehistoric demography. Journal of Archaeological Science 34, 1868–1877.] that explored the problem of taphonomic bias. Taphonomic bias refers to the tendency for younger things to be over-represented relative to older things in the archaeological record due to the operation of destructive processes like erosion and weathering. Using a database of radiocarbon dated volcanic deposits from Bryson, R.U., Bryson, R.A., Ruter, A. [2006. A calibrated radiocarbon database of late Quaternary volcanic eruptions. Earth Discussions 1, 123–124.], we develop an empirical model of taphonomic bias. In contrast to our prior study in which we modeled taphonomic bias as an exponential function wherein the likelihood of site loss remains constant through time, we argue that the probability of site destruction actually decreases with site age. We further demonstrate how this model can be used to correct temporal frequency distributions and extract demographic histories. We illustrate this approach using databases of radiocarbon dates from rockshelter and open-air sites in the Bighorn Basin, Wyoming, USA, and mammoths and humans in Siberia, Russia.     

基于环境犯罪学理论的入室盗窃时空分布研究——以北京市主城区案件的分析为例

以往关于犯罪时空特征的研究较多的侧重于对犯罪时空分布现象的描述分析以及从人文地理视角下的环境影响性分析,但缺少从环境要素与犯罪主体行为之间的相互作用机制下的犯罪时空特征研究。本文通过开展北京市入室盗窃案件的时空热点实证分析,总结和归纳了案件热点环境的时空要素类型,并基于环境犯罪学的基本原理,构建了基于犯罪主体与环境影响要素相互作用的犯罪时空分布机制,其中,环境对犯罪主体的影响主要表现为四类要素,即目标、交通、防范和作案时机。这些研究可以为下一步开展犯罪模拟以及犯罪预防提供借鉴。     

A method for chronological apportioning of ceramic assemblages

Artifact assemblages from long-inhabited sites may include ceramic types and wares from multiple time periods, making temporal comparisons between sites difficult. This is especially problematic in macro-regional data sets compiled from multiple sources with varying degrees of chronological control. We present a method for chronological apportioning of ceramic assemblages that considers site occupation dates, ceramic production dates, and popularity distribution curves. The chronological apportioning can also be adjusted to take into account different population sizes during the site occupation span. Our method is illustrated with ceramic data from late prehispanic sites in the San Pedro Valley and Tonto Basin, Arizona, U.S.A., compiled as part of the Southwest Social Networks Project. The accuracy of the apportioning method is evaluated by comparing apportioned assemblages with those from nearby contemporaneous single component sites.     

Free and mobile brachiopods from New Zealand Oligocene deposits and Australian waters

The musculature of the Recent Australian species, Magadina cumingi (Davidson 1852), is revised and previously unknown dorsal median pedicle muscles are described. The behaviour of M. cumingi is analysed in relation to the physical properties of the bryozoan sands it occupies on the Australian shelf. Functional morphology of a New Zealand Oligocene species, Rhizothyris amygdala Thomson 1920, indicates that this species would also have lived as a free and mobile form in the originally unconsolidated sediments (greensands) in which it is preserved. Shell characters of members of both Magadina and Rhizothyris are incompatible with an attached sedentary existence.     

The Firing Temperature of Pottery from Ancient Mesopotamia,Turkey, Using Luminescence Methods: A Case Study for Different Grain‐Size Fractions

The assessment of the firing temperature of a prehistoric pottery sample collected from ancient Mesopotamia, Turkey was studied using luminescence techniques. The methods for this estimation involved the observation of the thermal and pre‐dose sensitization with various re‐firing temperatures for both TL and the OSL signals. In the former case, the 110°C TL peak and the rest of the glow curve were used as proxies in this study. In the framework of a first attempt to investigate the impact of grain‐size dependence on the sensitization of the luminescence signals, the aforementioned study was performed with four different pottery grain‐size fractions: (i) less than 60 μm, (ii) 60–90 μm, (iii) 90–180 μm and (iv) 180–250 μm. The results clearly demonstrated the firing temperature mark of ～500°C in for the grain size of 90–180 μm, while—as in the case of the lower grain‐size fraction—a third proxy, the ratio of the pre‐dosed to the thermal sensitization, was seen to indicate the firing temperature. The remaining two grain‐size fractions failed to provide any meaningful results with regard to the firing temperature estimation. The dependence of the TL characteristics on the grain size was explained in the framework of the mixed mineralogy.     

Representations of birds in Minoan art

During the second millennium BC , the Minoan civilization was established in the southern Aegean Sea. In Minoan art, especially on Crete, birds occupied a prominent place, and were often represented in wall-paintings and craft objects. Species still occurring on the island, such as cormorants, mallards, cuckoos, owls, hoopoes, and swallows, as well as exotic taxa such as partridges and possible domestic forms such as pigeons, were the subject of artistic inspiration, and they were depicted not only in purely cult contexts, but also in the backgrounds of naturalistic landscapes. The aim of this paper is to reconsider the identification of some of the birds depicted and to discuss them in the context of the environmental conditions and osteological finds from the southern Aegean islands in Minoan times. © 1997 John Wiley & Sons, Ltd.     

Equivalent dose distributions from single grains of quartz at Sibudu,South Africa: context,causes and consequences for optical dating of archaeological deposits

Optical ages for 14 sediment samples collected from the post-Howiesons Poort, late Middle Stone Age (MSA) and final MSA deposits at Sibudu, KwaZulu-Natal, South Africa were reported in a companion paper (Jacobs, Z., Wintle, A.G., Duller, G.A.T., Roberts, R.G., Wadley, L. New ages for the post-Howiesons Poort, late and final Middle Stone Age at Sibudu, South Africa. Journal of Archaeological Science, 2008). These ages were based on equivalent dose (D_e) distributions that were overdispersed. In this paper, we investigate factors both internal and external to the grains that may contribute to such higher than expected overdispersion in single grain D_e values. Intrinsic factors accounted for some, but not all, of the observed scatter, and application of a set of rejection criteria filtered grains for which erroneous D_e values would otherwise be calculated. We investigated sediment mixing and differences in the beta dose received by individual grains in their burial environment as two likely reasons for the observed overdispersion. The scatter in D_e distributions for all the samples is best explained by grains that were deposited at the same time and which were well bleached, but that subsequently received a range of beta doses. A procedure is presented for adjusting the measured beta dose rate, and its associated error. We show that using a combination of single grain OSL measurements of D_e, the finite mixture model and adjustment of the beta dose rate, result in stratigraphically consistent ages. These ages are more consistent than the ages obtained from multiple grain aliquot D_e values and the average dose rates for each sample; the multiple grain ages are about 10% older, partly because of the variable dose rate and partly because these aliquots contained grains with undesirable OSL characteristics.