James H. Burton

The characterization of biologically available strontium isotope ratios for the study of prehistoric migration

Strontium isotope analysis of bone and tooth enamel from prehistoric human skeletons is an important new technique used to address questions regarding migration. Two problems arise in such investigations: (1) levels of strontium isotope ratios in local bedrock, soil, water, plants and animals are variable; and (2) a range of values in human bone and enamel data make it difficult to distinguish some migrants from locals. Analysis of the bones of small animals provides a robust measure of local strontium isotope ratios and a reliable, if conservative, means for determining confidence limits for distinguishing migrants. Data from various geographical areas are presented here in a discussion of variability in strontium isotope values. Examples are provided using modern and prehistoric materials. We conclude with the recommendation that studies involving strontium isotope analysis should incorporate small animal samples for comparative purposes whenever possible.

Diagenesis in prehistoric bone: Problems and solutions

Abstract Post-depositional chemical alteration, or diagenesis, in prehistoric human bone is the major problem in the use of trace element analyses for dietary reconstruction. Following a review of recent studies of diagenesis, we discuss means for evaluating post-depositional chemical change in bone and for removing such contaminants. Three different procedures are described which reflect current efforts to evaluate and reduce the effects of diagenesis. These include (1) mechanical cleaning, (2) chemical cleaning through acid washing and (3) washing with a reducing agent. These procedures usually remove major contaminants, leaving significant potential of trace element analyses for the investigation of past diet.

The ratio of barium to strontium as a paleodietary indicator of consumption of marine resources

Abstract Seawater has an extremely low ratio of barium to strontium in comparison to terrestrial ratios. Low Ba Sr ratios are also found in marine species and in the bone compositions of prehistoric populations who subsisted on marine resources. Differences in the Ba Sr ratios of human bones can thus be used as a measure of the relative amounts of marine and terrestrial components of diet. Some cautionary tales are also presented.

Acid Extraction As a Simple and Inexpensive Method for Compositional Characterization of Archaeological Ceramics

Although compositional characterization is now de rigueur in investigations of archaeological ceramics, the conventional means of characterization, instrumental neutron-activation analysis (INAA), is expensive and beyond the practical reach of many; demand has rapidly outstripped supply. Less expensive and more accessible methods have been employed with success, including atomic-absorption spectroscopy (AA) (Bower et al. 1975; Sheridan 1989; Torres et al. 1984; Tubb et al. 1980) and inductively coupled pled plasma emission spectroscopy (ICP) (Hart and Adams 1983; Har t ett al. 1991). Although easily available, these spectroscopic tools have not been widely used because the sample preparation methods for bulk analysis, requiring total dissolution of the ceramic, involve a great amount of labor and use extremely hazardous and toxic chemicals (Bower et al. 1975; Sheridan 1989). Here we present an inexpensive technique to obtain compositional attributes of archaeological ceramics that uses widely available instrumentation, but which does not require either the hazardous sample-digestion procedures or much labor. Soaking powdered ceramic samples in dilute acid for a few weeks at room temperature produces solutions that can be precisely reproduced. Although the acid does not totally dissolve the ceramic paste, extracts of ceramics made from the same clay produce chemically similar solutions, and different clays produce solutions with different compositions, such that the method can be reliably used to compare and distinguish ceramics. We have empirically observed in several dozen studies and thousands of analyses that the method does provide archaeologically significant information. Our initial tests indicate that the method can resolve ceramic production loci intraregionally, and that, using ethnoarchaeological data, the method can distinguish the wares of individual potters. Because a number of archaeological projects are already successfully using this method, a description of the method is presented at this time to encourage further exploration and evaluation. Choices of what ceramics to analyze, how many sherds, and what statistical methods are used

Place of origin of prehistoric inhabitants of Aztalan, Jefferson co., Wisconsin

The archaeological site of Aztalan in southeastern Wisconsin is a large, palisaded complex of mounds and other structures along the banks of the Crawfish River in Jefferson County. The unusual nature of this settlement has been noted for many years and the origin of the inhabitants has been the subject of considerable debate. The similarities between the materials at Aztalan and other Mississippian period sites to the south in Illinois have long been noted. The largest center of the Mississippian culture at Cahokia near East St. Louis, Illinois, has often been cited as the likely home of the founders of Aztalan. Using strontium isotopes in human teeth and bone we examine the question of migration and the possibility of nonlocal individuals among the skeletal remains from Aztalan. Our results suggest that there were a number of foreign individuals among the locals. The isotopic signal for some of the foreigners matches values from Cahokia, but does not prove that this was their place of origin.

On the logic of archaeological inference: Early Formative pottery and the evolution of Mesoamerican societies

The 2005 articles by Stoltman et al. and Flannery et al. to which Neff et al. (this issue) have responded are not an indictment of instrumental neutron activation analysis (INAA) but, rather, of the way Blomster et al. (2005) misuse it and of the hyperbolic culture-historical claims they have made from their INAA results. It has long been acknowledged that INAA leads not to sources but to chemical composition groups. Based on composition groups derived from an extremely unsystematic collection of sherds from only seven localities, Blomster et al. claim that the Olmec received no carved gray or kaolin white pottery from other regions; they also claim that neighboring valleys in the Mexican highlands did not exchange such pottery with each other. Not only can one not leap directly from the elements in potsherds to such sweeping culture-historical conclusions, it is also the case that other lines of evidence (including petrographic analysis) have for 40+ years produced empirical evidence to the contrary. In the end, it was their commitment to an unfalsifiable model of Olmec superiority that led Blomster et al. to bypass the logic of archaeological inference.

Isotopic Studies of Human Skeletal Remains from a Sixteenth to Seventeenth Century AD Churchyard in Campeche, Mexico: Diet, Place of Origin, and Age

In AD 2000, construction activities in the central plaza of the city of Campeche, Mexico, led to the discovery of an early colonial church and an associated burial ground dating from the sixteenth and seventeenth centuries AD. During the subsequent rescue excavations, the remains of at least 180 individuals were unearthed from the churchyard. We have concluded a series of isotopic studies of these remains to obtain information on diet, status, place of origin, and date of burial. This work involves the application of both light and heavy isotope analyses to both tooth enamel and human bone. Carbon and oxygen isotope ratios were measured in tooth enamel and bone. Carbon and nitrogen isotope ratios were measured on bone collagen. Strontium and lead isotopes were measured in tooth enamel, and the ratios were compared to a large database for the Maya region. Radiocarbon dates were obtained for 10 of the skeletons to evaluate the date of burial and the period of use of the cemetery. The results of our study, interpreted jointly with mortuary information and conventional skeletal examination, provide detailed information on the overall burial population, a sort of collective life history of the deceased individuals. In the context of the historical background, new insights on living conditions, mobility, and diet of the founding generations in the colonial New World are obtained. A new and direct appreciation on life and death in an early multiethnic colonial Spanish town, including its historically invisible sectors—children, women, servants, and slaves—becomes possible.

The Use and Abuse of Trace Elements for Paleodietary Research

Recognition among bone-chemistry researchers that strontium enters bone in proportion to dietary levels has resulted in widely accepted yet erroneous inferences about the relationships among various elements in bone and past diet. One such inference is that more of any element in the diet translates directly to more of that element in bone. If an element is not biogenically incorporated within bone, or if biological levels are metabolically controlled, then that element will not reflect diet. A second erroneous inference is that strontium can be used to measure the dietary plant/meat ratio. Sr/Ca ratios in meat are generally lower than those of plants, but meat is also low in calcium and hence has little effect on the composition of bone. Plants, on the other hand, contribute substantially to bone composition. Variations in the strontium levels of bone thus more likely reflect differential consumption of plants rather than trophic position. Although efforts to determine plant/meat ratios from strontium and to draw dietary inferences from elements other than strontium and barium have not been successful, this failure has been due to inappropriate expectations, not to a failure of bone strontium to reflect diet.

Evaluation of bone strontium as a measure of seafood consumption

The recognition that bone strontium/calcium ratios reflect dietary levels of strontium and that seawater has a high strontium content led some archaeologists to infer that seafood consumption produces high Sr/Ca ratios in bone. Analyses of seawater and of marine organisms reveal, however, a marine trophic effect comparable to the trophic effect seen in terrestrial food chains. This marine trophic effect reduces the Sr/Ca levels in seafood such that marine dietary resources have Sr/Ca levels comparable to those of terrestrial resources. Thus, bone Sr/Ca ratios can not differentiate consumption of marine and terrestrial resources. Also, Sr/Ca of bones from archaeological sites where seafood was an important component of diet were found to be within the range of entirely terrestrial diets. Copyright

A Taphonomic Approach to Late Classic Maya Mortuary Practices at Xuenkal, Yucatán, Mexico

Abstract Following a brief introduction to mortuary practices in Prehispanic Maya society, we outline the analytical procedures followed during the excavation and laboratory investigation of five burial assemblages from the Late Classic period site of Xuenkal, Yucatán, Mexico. A detailed account of a sequence of primary and secondary interments is provided with a focus on taphonomic and biovital information, emphasizing the importance of an interdisciplinary approach, especially human taphonomy, for the reconstruction of complex Maya mortuary treatments. Our results show that bodies of the dead or their parts followed surprisingly long and complex funerary paths.