The oxygen isotope ratio (δ18O) in tissues is the outcome of both climatic and geographical factors in a given individual’s place of abode, as well as the physiology and metabolism of his organism. During an individual’s life, various rates and intensities of physiological and metabolic processes are observable in the organism, also within the bone tissue.
The aim of this study is to verify whether involutional changes occurring as a result of the organism’s ageing have a significant impact on δ18O determined in the bone tissue.
The material used for analysis was fragments of the long bones taken from 65 people, (11 children and 54 adults), whose remains had been uncovered at the early mediaeval (X–XI century) cemetery located at the Main Market Square in Kraków (Poland).
The correlation analysis between δ18O of bone tissue and an individual’s age shows that up to 40 years of age, such a relationship does not exist in both, males and females. However, the conducted correlation analysis prompted the observation that after 40 years of life, δ18O in bone tissue significantly drops as females increase in age.
Results suggest that the δ18O in bone tissue among older people may be the outcome not only of environmental factors but also involutional changes in bone linked to an organism’s ageing. Therefore, the interpretation of δ18O results relating to the description of the origin and migrations of older individuals should be treated with caution.
The main objective of oxygen isotope analysis is to determine the probable place of origin of an individual or the reconstruction of migration paths. The research are methodologically based on referencing oxygen isotope ratios of apatite phosphates (δ18Op) to the range of environmental background δ18O, most frequently determined on the basis of precipitation.
The present work is a response to the need for providing background for oxygen isotope studies on skeletons excavated in Poland. Currently there no monitoring of the isotope composition of precipitation water in Poland is conducted. For this reason, based on the data generated in the Online Isotopes In Precipitation Calculator (OIPC), a database was developed, containing δ18O levels in precipitation for locations in which exploration work was carried out in the archaeological fields from Poland. In total, 279 locations were analysed. The result of the data analysis was a complete isotope composition map for Poland with four zones distinguished by δ18Ow values.
The observable differences in oxygen isotope composition of precipitation in Poland are sufficient to trace migrations of individuals and populations, although accurate only at the level of macroregions.
Isotope analyses of bones and teeth allow us to study phenomena which occurred in the history of human species and which are difficult to capture by traditional anthropological methods. Measuring oxygen, nitrogen and carbon isotope levels in the skeleton makes it possible to reconstruct climatic changes, diet and/or the weaning process. Among isotopes used in such analyses are strontium isotopes, helpful in analysing migration and studying the mobility of historical and prehistoric human populations. In this respect, the proportion of two isotopes, the heavier 87Sr and the lighter 86Sr, is measured, following their extraction from the bioapatite of the bone mineral. Released from rocks in the weathering process, strontium permeates individual components of inanimate and animate environments, and then finds its way, together with food, to the human body. Thanks to comprehensive environmental studies and the measurement of the strontium ratio 87Sr/86Sr in various animal tissues it is possible to determine the local isotope background for the environment. Values obtained by analysing human skeletons referenced against the range of environmental isotope variability enable researchers to trace back the location inhabited by the individual or group.
Stable isotope analyses of oxygen are used in anthropology for such purposes as determination of origin of individuals, tracking migration routes or dynamics of human community relocation. The methodology related to oxygen isotope analysis has been founded on the relationship between its isotopic composition within phosphate groups of bone tissue (δ18Op) in individuals being analysed and the water consumed by such individuals (δ18Ow). Such a relationship has been observed in many species of mammals, including humans. However, the influence of culinary practices on the isotopic delta values of apatite phosphates of individuals has not yet been researched. The present study, which was conducted using laboratory rats, is an investigation of the influence of the thermal processing of water drank by such rats on the isotopic composition (δ18Op) of bone apatite. Increasing the value of the isotopic composition of water by about 6.1 ‰ during boiling resulted in an increase in the oxygen isotopic value δ18Op of rats drinking the water by about 4 ‰ (29%). It can be expected that regular consumption of heavily isotopic drinks and foods by humans may cause the δ18Op of individuals to exceed the range of isotopic environmental variability, even by a few per mille.
Diagenetic signals from ancient human remains - bioarchaeological applications
This preliminary study examines the potential effects of diagenetic processes on the oxygen-isotope ratios of bone and tooth phosphate (δ18O) from skeletal material of individuals representing the Corded Ware Culture (2500-2400 BC) discovered in Malżyce (Southern Poland). Intra-individual variability of Ca/P, CI, C/P, collagen content (%) and oxygen isotopes was observed through analysis of enamel, dentin and postcranial bones. Using a variety of analytical techniques, it was found that, despite the lack of differences in soil acidity, not all the parts of a skeleton on a given site had been equally exposed to diagenetic post mortem changes. In a few cases, qualitative changes in the FTIR spectrum of analysed bones were observed. The data suggest that apart from quantitative analyses, i.e., the calculation of Ca/P, CI, C/P and collagen content, qualitative analyses such as examination of the absorbance line are recommended. The degree to which a sample is, contaminated on the basis of any additional, non-biogenic peaks, deemed to be contaminated should also be specified.