|Abstract (english)|| |
The dissertation is a bioarchaeological and biochemical analysis of human bone Bronze Age samples from ten sites across the eastern Adriatic coast, focusing specially on collagen-based stable isotope analysis of carbon ( 13C) and nitrogen (15N) of the said samples, in the goal of creating a more detailed picture of past dietary habits of this region. Stable isotope analysis of this kind is a method which has been used for almost half a century in diet reconstruction of past populations, but has only now been utilized in Croatia proper, though there were earlier analyzes conducted on Croatian samples in the past years. A complex prehistorical period in terms of various cultural practices and equally diverse material legacy from numerous sites, both in continental and coastal Croatia, the Bronze Age thus provides a complex challenge. This type of research requires an interdisciplinary approach, where bioarchaeology can provide a valuable insight into pathologies visible on osteological and odontological material, while biochemistry can combine the data gained through elemental analysis with the traces visible on bones, therefore acquiring a more complete frame of reference for continuing work in this regard. The relation between diet and pathologies visible on bones is often intrinsically connected. Indicators such as linear enamel hypoplasia and dental asymmetry can be used during determination of archeological populations' subsistence strategies. Scurvy, for example, is an excellent example of metabolic stress caused by prolonged vitamin C deficiency, invaluable in collagen synthesis, one of the key components in bone. Rickets is a disorder by vitamin D deficiency, which prevents bone calcification and makes it brittle and fragile. However, many signs of physiological stress on bone are often nonspecific, and can only imply diet stress, but not its origin. Biochemical approach to the same problem can produce more concrete results, and thus stable isotope analysis—especially those of 13C and 15N—have played an increasingly more prominent role within bioarchaeology/bioanthropology as well as in classical archeology in recent times. Different stable isotopes provide diverse information regarding various aspects of life of archeological populations. Values of stable isotope of carbon can point to a specific plant-based diet, while nitrogen values can indicate levels of protein intake. For example, the more negative δ 13C values show a diet based on the C3 plants, the most expansive type of plants on the planet, whereas the more positive values imply a certain intake of C4 plants—yet another type of plants which makes up approximately 5% of the entire flora on Earth. Similar to that, the higher values of δ 15N will suggest not only animal-based diet (which will, automatically, elevate the sample to a higher trophic level), but will also point to sea-based foodstuff, because of the higher concentration of nitrogen within aquatic ecosystems. It is, however, important to note that to interpret and calibrate the results, human samples have to be of the same type, as different bones exhibit different resorption times, which means varying isotope results, mirroring different diet during the entire lifespan. Along with that, faunal samples from either the same site and/or period are necessary to establish a proper reference point (baseline) for the primary samples, and thus place them more correctly within the ecosystem. Seventy-five coastal samples from various Bronze Age Croatian sites—plus one Montenegrin— form the basis of this research, while ten from the Croatian continent serves as a geographical comparison of life trends and dietary habits. The primary reason for such a comparison lies in the strategic importance of the Adriatic Sea, both as a commerce center and a source of food the locals might have exploited. This research represents the largest interdisciplinary biochemical study of this geographical area in the form of stable isotope analysis of carbon and nitrogen extracted via collagen as to broaden the understanding of the type of diet ancient residents had enjoyed, as well as the type of pathologies that had plagued them. Since the Bronze Age samples are often not well preserved due to age and thus taphonomy, most osteological samples have raised certain problems in the bioarchaeological sense, especially in the sexing and aging aspect, which prevented any firm conclusions based on social stratification. However, since the focus of this study is the reconstruction of diet, the primary aspect lies within the observed pathological changes and the isotopic values that may have affected such conditions. While at least one study published so far shows certain correlations of such isotopic values with bioarchaeological results and macroscopically noticed pathological changes (Martinoia et al. 2021), the samples presented here do not explicitly exhibit such trends, though there are indications of nonspecific metabolic stresses among certain individuals. In both coastal and continental samples, a visible increase in consumption of a C4 plant—most probably millet, judging by the latest radiocarbon dates of millet seeds and archaeobotanical finds across European Bronze Age sites (Filipović et al. 2020)—is evident through time. A crop of drier climates, millet is highly resistant to sudden weather changes, with ripening time of approximately three months, which makes it a perfect nutriment for larger populations. As a period of vast social changes and a more pronounced sedentism which—in turn—led to the foundation of larger settlements, a sharp increase in food demands undoubtedly colored that aspect of the Bronze Age, and millet—as a highly resistant crop—could have played a vital role in the next stage of mankind's expansion, both from a biological and cultural perspective. As previously mentioned, the new radiocarbon dates from Filipović et al. 2020 show that the cultivation of millet as a new foodstuff had its origin in the east, and then spread westward throughout Europe, with sea routes playing little to no role in its expansion, at least as far as recent studies imply. This is also visible in the isotopic results presented in this study, where coastal samples show a marked deviation from a supposed standard of populations from that geographical area, as their values do not indicate a significant intake of seafood of any kind, be it floral or faunal. While fishing has been a mainstay among sea-faring or sea-adjacent peoples since at least the Mesolithic, and Bronze Age being famous for the many world-famous maritime epics (i.e. Iliad and Odyssey), there is no question regarding the old ones' lack of skill or expertise in that area. Instead, it seems more probable to discuss the unprofitability of fishing, and the sheer quantity of such foodstuff needed when compared to the more easily obtainable, resistant crop like millet, which could quench the needs of a larger number of people with relatively less effort. This is not to say the Bronze Age inhabitants of the eastern Adriatic coast had not consumed marine food at all; more probable is the possibility that they had exercised a balanced, maritime-continental subsistence strategy, where carbohydrates had been their primary, everyday nutriments, as it was to their continental counterparts.