J Archaeol Sci 34 (11)

The authors present a new climate and vegetation model, and discuss applications with a study of medieval land degradation and settlement abandonment in þórsmörk, Iceland. Existing meteorological data are used as the starting point for modelling glacier snowlines (equilibrium lines), and this is developed to model seasonal snowcover, potential vegetation and growing season. The current status and past fluctuations of glaciers across Iceland provide independent spatial and temporal constraints to the model. In þórsmörk, there was extensive landscape degradation and settlement abandonment in the late Medieval period, with an unclear role for climate change. Modelling of the landscape impacts of a 1 °C fall in temperatures shows that climatically induced degradation through reduced vegetation, growing season, and increased snowcover had limited effects on the once settled area, highlighting the importance of anthropogenically driven change. High resolution modelling offers a significant potential for assessing `what if' questions, and identifying key empirical tests.

The purpose of this study was to compare three different collagen extraction methods commonly used in isotope laboratories conducting dietary studies. The authors evaluated their resultant differences in δ13C and δ15N, collagen quality and collagen yield. . The study was based on well-preserved skeletal material from the medieval period in Denmark; it shows that there is a systematic significant difference in the yield and the δ13C values between the three methods. Using the method of DeNiro and Epstein (M J DeNiro and S Epstein, `Influence of diet on the distribution of nitrogen isotopes in animals' in Geochimica et Cosmochimica Acta 45 (1981), pages 341--51) with NaOH as cleaning agent, would, according to the study, give δ13C values that are on average ±0.32o/oo more positive than using the ultra-filtration method (T A Brown, D E Nelson, J S Vogel and J R Southon, 1988. `Improved collagen extraction by modified Longin method' in Radiocarbon 30:2 (1988), pages 171--7, modified in M P Richards and R E M Hedges, `Stable isotope evidence for similarities in the types of marine foods used by late Mesolithic humans at sites along the Atlantic coast of Europe' in Journal of Archaeological Science 26 (1999), pages 717--22). The third method, which is a modified version of the second method, excluded the ultra-filtration step. This method seems to give δ13C values that lie in between the other methods. The study did not show any significant difference in δ15N values. Although the differences between the methods are very small, the authors conclude that the use of stable isotope analysis in food determination studies requires adherence to routine methods for preparing and measuring samples.

Temporal frequency distributions of archaeological sites and radiocarbon dates are commonly used as proxies for prehistoric population levels based on the assumption that more people create a stronger archaeological signal. The authors, while acknowledging that this assumption is certainly correct, question whether relative frequencies of sites or dates observed from prehistoric contexts are necessarily linked to human demography. They demonstrate that the typical positive curvilinear frequency distributions observed in archaeological contexts also regularly occur in paleontological and geological contexts and are thus likely caused by the operation of time-dependent destructive processes, known as `taphonomic bias'. Using a simple model, which assumes a constant rate of site loss over time, they show how taphonomic bias can produce positive curvilinear frequency distributions through time even in cases of population stasis, decline, and fluctuation. They conclude that caution must be used when attempting to infer demographic trends from frequency distributions alone.

Early research suggests that examination of the microscopic internal structure is a valid method for distinguishing burned from unburned bone in the archaeological record. The study compares burned and unburned modern bones with archaeological bones from Sibudu Cave (ca. 60,000 years ago) and Cave of Hearths (over 200,000 years ago), South Africa, to more fully describe the heat-induced histological changes to bone. The authors also explore the effects of diagenesis on those changes to determine if histological evidence of burning preserves through fossilisation and diagenetic processes and can be successfully used to identify ancient burning. It is argued that application of this technique can help in addressing various issues, including the origins of controlled use of fire and understanding animal butchery and disposal.