Studying the process of enamel powder preparation for émail champlevé by colour measurements and μ‐X‐ray mappings

Colour measurements and non‐destructive μ‐X‐ray mappings have been used for the first time in a comprehensive study of medieval émail champlevé works from different production areas in France and Germany. This approach has given a new insight into the enamel powder preparation process of the glass material used for enamelling. Colour measurements demonstrated that all production centres used glass of very similar hues, but with large differences in colour saturation. The μ‐X‐ray mapping results of blue enamels are described by a semi‐qualitative approach. Significant variations in oxide contents of lead, cobalt, manganese and antimony oxides were found. The variations suggest that more than one glass material was used to prepare the powder for enamelling. The variations in antimony and cobalt show that glass had different degrees of opacity and colour depth. The manganese and lead contents, which do not correlate with the cobalt or antimony contents, indicate that probably glass of different base compositions was used to prepare the enamel powder for one champlevé field.     

Do silica phytoliths really wear mammalian teeth?

There is considerable literature suggesting that silica (opal) phytoliths cause dental enamel microwear in mammals. Much of this literature cites a single study from 1959 as evidence that silica phytoliths are harder than mammalian tooth enamel and so have the potential to cause dental microwear. No other studies using similar methodology have actually confirmed whether phytoliths are harder than dental enamel.     

Health Consequences of European Contact in the Great Plains: A Comparison of Systemic Stress Levels in Pre‐ and Post‐Contact Arikara Populations

The biocultural effects of European contact varied considerably throughout the Americas. Some populations were decimated by colonialism, while others benefited from trade relationships and access to new technologies. It has been suggested that initial contact with European fur traders and explorers was economically favourable for Plains village populations, thereby facilitating a period of cultural florescence. In this study, we evaluate the hypothesis that Plains groups were better off than their predecessors during the initial contact period by comparing frequencies of enamel hypoplasia, cribra orbitalia, and porotic hyperostosis in pre‐ and post‐contact Arikara skeletal assemblages. We included both juveniles and adults in our sample to capture variation in the stress experience of different segments of the population. Our analysis revealed similarly low frequencies of cribra orbitalia in the pre‐ and post‐contact groups and no observed cases of porotic hyperostosis. Enamel hypoplasia, however, was significantly more prevalent among post‐contact Arikara villagers when compared to their pre‐contact counterparts, which suggests that stress levels were higher after European contact. Additionally, enamel hypoplasia was most common among post‐contact juveniles. The elevated frequency of enamel hypoplasia in the post‐contact sample combined with the low frequencies of cribra orbitalia and porotic hyperostosis suggests that disease stress, rather than nutritional deficiencies, was likely responsible for the decline in overall health following European contact. These results also suggest that juveniles are sensitive indicators of systemic stress within a population and should be included in bioarchaeological analyses of prehistoric health when available. Copyright © 2015 John Wiley & Sons, Ltd.     

Biocultural Consequences of Spanish Contact in the Lambayeque Valley Region of Northern Peru: Internal Enamel Micro‐Defects as Indicators of Early Life Stress

The present study utilises dental histological methods to analyse enamel micro‐defects as indicators of early life stress in indigenous Muchik individuals interred at two sites: La Capilla Santa María Magdalena de Eten (CSMME) (n = 15) and La Capilla del Niño Serranito (CNS) (n = 15), both located in the Lambayeque Valley region of northern Peru. Individuals interred at CNS date to the Early Colonial Period (AD 1533–1610), and individuals interred at CSMME date to the Middle/Late Colonial Period (AD 1625–1760), thus permitting comparison of childhood stress events between the Early and Middle/Late Colonial Periods. Results reveal a high prevalence of Wilson bands at both sites, although a lower prevalence at the CSMME was observed in comparison with the CNS. This indicates that, over time, Muchik individuals in this town may have been able to acclimate to life under Spanish oppression. Stress chronologies suggest that early life stress possibly resulted from inadequate and less than desirable food and/or water available for supplemental feeding during early infancy, especially around the ages of 4 and 5 months. Furthermore, results show that individuals with enamel defects in the form of Wilson bands at both the CNS and CSMME had an earlier mean age‐at‐death (9.6 and 4.05 years, respectively) in comparison with those without observed Wilson bands (19.75 and 8.8 years, respectively). These results underscore the importance of not only regional and temporal studies of the biological consequences of Spanish contact in the Americas but also of investigating the relationship between early life stress and adult health and longevity in archaeological populations. Copyright © 2015 John Wiley & Sons, Ltd.     

Exponentially decreasing tooth growth rate in horse teeth: implications for isotopic analyses

A range of archaeological and palaeoclimatic studies use isotopic analyses of ungulate hypsodont tooth enamel. Such studies commonly assume a constant growth rate, though this has not been fully tested. Here, we use stable isotope analyses of sequential enamel samples to study horse tooth growth. We fit the data using models corresponding to constant and exponentially decreasing rates of growth, and compare the results to metrical data showing the geometry and timing of apposition. The results indicate enamel apposition and maturation advances at an exponentially decreasing rate. An understanding of this variable growth rate is crucial for interpreting isotopic data from equid teeth.     

Neolithic nomadism in south‐east Arabia — strontium and oxygen isotope ratios in human tooth enamel from al‐Buhais 18 and Umm al‐Quwain 2 in the Emirates of Sharjah and Umm al‐Quwain (UAE)

Human skeletal remains from the Neolithic sites BHS18 in the interior of the Sharjah Emirate and the Neolithic shell midden UAQ2 (Umm al‐Quwain) on the coast of the Persian Gulf (United Arab Emirates, UAE) were analysed for their isotope ratios of strontium (⁸⁷Sr/⁸⁶Sr) and oxygen (¹⁸O/¹⁶O). The results are not in agreement with earlier assumptions about a Neolithic nomadism between inland regions and the south‐eastern coast of the Persian Gulf. Existing evidence of nomadic movements of the people from BHS18 most possibly refers to transhumance within the mountains in the hinterland. The strontium isotope measurements on human skeletons from UAQ2 on the contrary indicate uninterrupted residence of this population on the coast. Nevertheless, evidence was found of individual mobility between inland regions and the coast.     

Problems and pitfalls in the diagnosis of linear enamel hypoplasia in cheek teeth of cattle

Prevalence and intensity of enamel hypoplasia have been used as markers of generalized physiological stress during dental development in a wide range of mammalian taxa. We studied cattle (Bos taurus) cheek teeth exhibiting morphological characteristics that are of relevance to the diagnosis of enamel hypoplasia in this and other bovid species. These characteristics were multiple, more or less horizontally arranged (waveform) lines or grooves in the cementum of the tooth crown and the adjacent root area, leading to an imbricated appearance of the cementum. On macroscopic examination of tooth surfaces, these lines resembled linear enamel hypoplasia (LEH). Microscopic analysis of tooth sections, however, revealed that the lines occurred in the cementum only, and that the underlying enamel did not exhibit morphological irregularities. In cheek teeth of older cattle, a thick cementum layer is regularly found in the cervical crown portion and the adjacent root area. Apposition of this cementum is related to the uplifting of the teeth from their alveoli, a process that compensates for the shortening of the tooth crowns due to occlusal wear. In the studied specimens, a pronounced periodic nature of tooth uplifting and the related deposition of cementum is the likely cause for the observed imbricated appearance of the cementum. While this phenomenon may be misinterpreted as representing a case of LEH, presence of enamel hypoplasia in bovid teeth may be overlooked when the defects become filled with coronal cementum and are therefore not apparent on external inspection. This was the case in one of the cattle teeth analyzed by us, in which the hypoplastic enamel defects were, however, clearly discernible in ground sections. Microscopic analysis of tooth sections is recommended for recording of LEH in bovid teeth in cases where macroscopic examination of tooth surfaces alone does not produce unequivocal results.     

运用科学技术方法对清代珐琅的研究

作者运用原子发射光谱、扫描电子显微镜、偏光显微镜和金相显微镜,对故宫博物院藏清代珐琅残片进行了实验分析。研究中.对构成珐琅的硅酸盐材料、铜材料、焊接材料以及镀金层的元素组成进行了测试;对珐琅残片断面的焊接层和镀金层的微观形貌、焊接层的金相组织进行了观察和鉴别。在此基础上,运用结晶学、矿物学、金属学和金相学的基础理论对珐琅原料种类、各种原料的作用、珐琅料的熔制与烧蓝、铜材料与焊接材料的合金属性、焊层的金相组织、掐丝珐琅的烧制工艺等问题加以探讨,试图藉现代科技手段揭示清代珐琅所包含的科学技术内涵。     

An inter-site comparison of enamel hypoplasia in bison: implications for paleoecology and modeling Late Plains Archaic subsistence

Bison bison mandibular molars from the Late Plains Archaic kill/butchery sites of Buffalo Creek (Wyoming) and Kaplan-Hoover (Colorado) exhibit significant frequencies of dental enamel hypoplasia (DEH), a defect believed to reflect information about physiological status of individual animals. This study provides a methodology to estimate the ontogenetic and seasonal timing of DEH formation in bison dentition. Integration of these estimates with data from bison life history and grassland ecology allows inferences on age- and season-specific factors exacerbating periodic physiological declines that were recorded in the form of enamel hypoplasias. Differences between assemblages indicate regional variability in grassland conditions, with data from Buffalo Creek pointing to recurrent drought that reduced forage capacity and contributed to physiological stress in bison over two consecutive years. Seasons of physiological stress reflected in the DEH correspond to each of the three kill events at the locality, suggesting that predictability of bison behavior in this location was a critical factor in influencing the seasonal timing and location of repeated hunting episodes. Unlike Buffalo Creek, timings of stress episodes are not consistent with season of death in the Kaplan-Hoover bison assemblage, suggesting that favorable grassland conditions were the primary factor influencing timing of this large single-kill event in order to provision for the upcoming winter. DEH analysis represents a developing approach in the construction of models addressing key aspects of local grassland and bison ecology as well as offers unique insights into the hunting strategies and subsistence decisions of Late Plains Archaic foragers.