J Archaeol Sci 32 (3)

The application of bone collagen stable carbon and nitrogen isotope analysis to human palaeodietary reconstruction in tropical or arid regions is limited by the overlap in C4 and high marine protein (HMP) consumer bulk collagen 13C values, and the unpredictability of bulk collagen 15N values in regions of extreme aridity. To identify a more precise marine palaeodietary indicator, a range of collagen samples from archaeological faunal and human bone (n=14 and 26, respectively), representing a spectrum of C3, C4 and HMP diets, were selected from coastal and near-coastal sites in South Africa. Samples were subjected to compound-specific stable carbon isotope analysis of their constituent amino acids as trifluoroacetyl-isopropyl (TFA-IP) esters via gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). It was concluded that 13CGlycine-Phenylalanine values offer considerable potential as indicators of HMP consumption and a valuable substitute for bone collagen 15N values in arid regions where bulk 15N values are unpredictable.

Low altitude sandy plains (machair) are a distinctive feature of the Atlantic coasts of the Scottish Outer Hebrides. They formed as a result of shoreward movement of sediment consequent upon a rise in Holocene sea levels. During the long period over which machair has been forming, the earliest date proposed for their human occupation is the Neolithic. The natural origins of the machair are not disputed, but examination of deposits at sites in the islands of Benbecula and Grimsay encourages the authors to advance a possible anthropogenic role in the process of machair development, and also to suggest that human involvement may date from the Mesolithic period (pre-5000 BP [ca. 5730 cal BP]), a time for which archaeological evidence is lacking from the Outer Hebrides. They also argue that the presence of charcoal might suggest that burning of the vegetation cover of the machair was an additional factor to the supposedly dominant marine and aeolian processes in sand mobility, and that removal of shrub vegetation may also have left sand surfaces open to deflation. There remains a difficulty in separating natural from human causes in investigations of long-term coastal evolution.