Bone chemistry

Special issue on bone chemistry, including contributions on

mammalian tooth enamel carbonates from a Pliocene site in Kenya show variable carbon and oxygen isotopic alteration. Sample screening by cathodoluminescence, prior to isotopic analysis, identified areas of extensive chemical alteration and others that were minimally altered. The luminescent patterns were used to guide sampling for the isotope study

the paper considers research which has shown that calcium isotopes are fractionated by metabolic processes, leading to a decrease in 44Ca/40Ca ratio with increasing trophic level. It is argued that if this is so, calcium isotopes could provide information on trophic relationships within foodwebs millions of years older than what it has been possible to study thus far with alternative methods (i.e., nitrogen isotopes (15N), Sr/Ca). To explore whether 44Ca values provided marine trophic level information, the authors measured the 44Ca composition of tooth enamel and bone from modern marine mammals representing a 2.5 order range in trophic level. Marine mammal enamel 44Ca values clustered into two groups -- mammals foraging on vegetation or invertebrates exhibited higher 44Ca values than those foraging on fish or other marine mammals. They next examined whether this correlation was preserved in the fossil record by examining a 15 Ma marine fauna from southern California and observed that the relationship between 44Ca values of specimens followed the same pattern as observed in modern faunas, but the mean 44Ca values were significantly different from modern 44Ca values for mammals of similar trophic level. They conclude that the relative spacing of 44Ca values amongst fossil taxa can serve as a valuable tool for defining trophic level of extinct organisms and can provide critical information on relationships within ancient foodwebs

prey-predator collagen enrichment values for carbon and nitrogen isotopic compositions are investigated. New enrichment values are given for the well-monitored ecosystem of Bialowieza primeval forest (Poland) for lynx and wolf. The impact of using different approximations in calculating such enrichment values is discussed. Several case studies of ancient vertebrate communities from Upper Palaeolithic sites in southwestern France are presented to check whether the enrichment values estimated for these past ecosystems are consistent with those measured in well-monitored modern ecosystems. The use of ranges of values rather than average ones is recommended

the paper addresses possible underlying causes of the observed systematic spacings in the carbon isotopic composition of bone collagen and bone apatite-carbonate when herbivores, omnivores and carnivores are compared. In particular it examines whether the observed systematic spacings are due to dietary differences, or to metabolic differences. It concludes that a simple model for diet-to-collagen isotopic fractionation (based on dietary difference) can account for half of the observed spacing, but probably not more than that. It also examines the role of methanogenesis and argues that this is a feasible explanation for ruminant and, to a lesser extent, hindgut fermenter, spacing values, although again it is difficult to account for the full amount observed. It also considers the implications of observations indicating that much of the change due to different diets in a given species is probably due to isotopic shifts in bone carbonate, rather than collagen, Includes

the authors present the results of a controlled feeding study designed to test the effects of gut anatomy and dietary protein levels on hair 15N values within a trophic level

while geologically significant differences of strontium (Sr) isotopic ratios in dental enamel and compact bone from adult human skeletal finds will be basically indicative of an individual residence change between early childhood and adulthood, hardly any information will be available with regard to the approximate individual age at migration. Due to several problems still associated with microsampling techniques, bulk analyses of appositionally grown mineralized tissues were analysed for 87Sr/86Sr ratios in an attempt to mathematically define the ontogenetic stage at individual residence change in historical times. This pilot study presents the results obtained from serial analyses of whole enamel from human permanent dentitions from a Roman fortress site in Germany, and serial sampling of a horn core from a long-horned ox from an early modern horn core site in Austria. In the first case, more detailed information was expected with regard to population admixture in the Roman provinces, while the horn core analysis was performed in an attempt to shed light on mode and velocity of long distance trade of domestic animals. A mathematical approximation served for the definition of the most likely individual age when Sr with a new isotopic composition first shows up in the course of tissue precipitation