Climate and seasonality reconstructions are typically undertaken when studying middens. In other sites land and freshwater snails are useful in reconstructing past environments. While both were rarely used for making beads, land snails often burrow into the archaeological sediments on their own while freshwater snails most often were inadvertently brought to the site either with mud for the construction of mud bricks, or with drinking water.
In addition, the presence of freshwater snails, especially Bulinus sp., which is the host of the Schistosoma worm, is sometimes taken to indicate the presence of schistosomiasis (bilharzia), a parasitic disease.
Radiocarbon dating of shells is possible but should be used cautiously and with correction for reservoir age. Differentiating between recent and fossil mol-lusks can be done either by radiocarbon dating, or by measuring strontium isotopic compositions (87Sr/86Sr). Specific shell artifacts may be a diagnostic tool for determining relative chronology similarly to pottery and lithic types (see Carbon-14 Dating; Dating Methods, Overview).
Methods for shell analysis are highly diverse and to date there are no standard methods. The growing number of professional meetings of archaeomalacolo-gists in recent years is likely to advance certain aspects of molluskan (as well as other invertebrates) analysis.
The description of a shell assemblage is based on identification and quantification. The basic step in the analysis of any invertebrate is species identification. Because of the broken and abraded nature of shells (that first rolled on the beach, then were manipulated by humans in antiquity, and finally were buried in archaeological sediments), the use of faunal guidebooks is often not satisfactory. The comparison to identified specimens in comparative collections in museums and other curated collections is required, and it is often necessary to compare to several identified specimens, also because of the natural (genetic) variability within each species. The analysis of shells that were used as ornaments is not always possible when the indicative body parts were cut or broken, but often faded remains of the spire or the natural sculpture of the shell can serve as clues, as well as their finding within debris in the case of workshops for shell ornament production. The next step will be determining the archaeological type (beads, pendants, bangles, etc.), which varies between geographic and temporal zones. Creating a typelist (similar to such lists used for pottery and lithics) is a useful tool for describing precise definitions of the types. It is often important to add a taphonomic description of the shells, that can indicate whether they were collected alive or dead, heavily abraded by the actions of the waves, wind and sand, or fresh (see Taphonomy). The proportions between complete shells, broken ones, and small fragments may be useful in determining the existence of a workshop versus the finished objects that may have been traded.
World History
