What Kind of Data Are in the Back Dirt? An Experiment on the Influence of Screen Size on Optimal Data Recovery

Zooarchaeological assemblages are non-renewable resources that provide a record of human culture and the paleoenvironment. Optimal sampling of zooarchaeological remains forms a foundation from which questions about human ecology are asked and answered. It has been known for over three decades that fine-gauge screen sieving (1/l6 inch = 1.58 mm) has an influence on the recovery of biological remains. However, archaeologists are not always fully aware of what types of faunal data may be lost into the back dirt, or the impact of those losses on interpreting the zooarchaeological record when fine-gauge screens are not used. As zooarchaeology has evolved to include studies of the paleoenvironment, sampling concerns have become even more important. This paper presents the analysis of the results of an experiment on the recovery of 10 zooarchaeological assemblages from coastal Alabama; Georgia; Florida; St. John, U.S. Virgin Islands; and Puerto Rico. When fine-gauge screen sampling protocol is used, large and small taxa have an equal chance of being recovered, and there is an exponential increase in the numbers of fish taxa and individuals recovered. Measurements of the lateral width of fish vertebrae in the 10 assemblages show that over 80% of the specimens are smaller than 6 mm and potentially would have been lost through coarse-gauge (1/4 inch = 6.35 mm) screen. The inclusion of remains recovered through finer meshes of screen significantly changes biomass calculations. Furthermore, descriptive statistics for sample diversity, equitability, trophic level, and similarity indices are affected. Fine-gauge screen recovers an assemblage of faunal remains that more closely resembles the midden population than do coarse-screened samples; therefore the fine-screened samples more accurately reflect the relative percentage of taxa and the size classes of the represented animals. The statistical data show that faunal assemblages recovered with different screen gauges are not directly comparable.Las asociaciones arqueozoológicas constituyen vestigios de recursos no renovables que documentan las culturas y los medios ambientes en el pasado. Un adecuado muestreo de estos restos genera una base a partir de la cual se pueden formular y responder cuestiones de distinta índole referidas a la ecología humana. Durante más de tres décadas hemos sabido que los tamizados con mallas finas (de 1/16 de pulgada = 1.58 mm) ha mejorado notablemente la recuperación de este tipo de restos. Aún así numerosos arqueólogos no son aún conscientes de los tipos de datos faunísticos que pueden perderse con los sedimentos desechados ni tampoco el impacto que estas pérdidas tienen sobre la interpretación del registro zooarqueológico. A medida que la zooarqueología derivó hacia los análisis paleoambientales el problema del muestreo ha adquirido una mayor importancia. Este trabajo presenta los resultados de un análisis experimental sobre la recuperación de 10 asociaciones zooarqueológicas de la costa de Alabama, Georgia, Florida, St. John en las Islas Vírgenes (EE.UU.) y de Puerto Rico. Al utilizar un protocolo de muestreo con cribas de luz pequeña los taxones de cualquier tamaño tienen igual probabilidad de ser recuperados al tiempo que se manifiesta un incremento exponencial en los números de taxones e individuos de peces que se recuperan. Las mediciones de la anchura de las vértebras de peces en estas 10 asociaciones demuestran que más del 80% de los especimenes son menores de 6 mm y podrían haberse perdido potencialmente de haber usado una malla más grande en el tamiz (1/4 de pulgada = 6’35 mm). La incorporación de restos recuperados con mallas más finas cambia significativamente todos los cálculos de biomasa. Además la estadística descriptiva referida a la diversidad de la muestra, la equitabilidad, el nivel trófico y los índices de similitud se ven fuertemente afectadas. Los tamices de malla fina recuperan asociaciones de restos faunísticos que se asemejan más a las poblaciones originales de los depósitos de lo que lo hacen las muestras recuperadas con tamices gruesos. Por lo tanto, las muestras de tamiz fino reflejan de modo más preciso el porcentaje relativo de taxones y las clases de tallas de los animales representados. Los datos estadísticos demuestran, por último, que las asociaciones faunísticas recuperadas con tamices de diferente luz de malla no son directamente comparables

“To be SOLD, for ready money”

Colonial Williamsburg’s Environmental Laboratory has an ongoing program of analysis of oysters from historic contexts in the Virginia Tidewater region. From this large-scale, multisite synchronic and diachronic research, a clear pattern of intensive oyster resource exploitation in Williamsburg throughout the seventeenth, eighteenth, and nineteenth centuries has emerged to throw more light on the value of such comprehensive research. Using often underutilized archaeological resources, this work underscores the value of a rigorous program of oyster research to answer questions of regional provisioning and environment, as well as the far-reaching effects political and market forces can have on resource availability, distribution, and harvesting.</p

Seasonal Shell Growth and Longevity in Donax Variabilis from Northeastern Florida: Evidence from Oxygen Isotopes

The variable coquina clam, Donax variabilis, is one of the most common inhabitants of exposed sandy beach intertidal and shallow subtidal zones in the southeastern United States. Its exceptional burrowing and migratory behaviors are well documented, as are its biogeograpbic distribution and phylogenetic relationships. However, basic life history parameters such as season and rate of shell growth and longevity are poorly constrained for this species, usually estimated from size-frequency analyses of sample populations. High-resolution sampling of individual D. variabilis shells, and analysis of the oxygen isotopic variation in these samples, provides an alternate method of assessing shell growth and longevity in this species with a high degree of precision. Comparison of isotopic paleotemperature profiles with local seawater temperatures in the northeastern Florida study region indicates rapid shell growth (>4 mm/month) during a life span of 3 to 5 months, substantially shorter than most previous estimates. Detailed analysis of two modern shells indicates growth during spring and summer whereas four Archaic period archaeological shells revealed a summer-autumn growth record. In all cases the largest archaeological shells were substantially bigger than the largest modern shells, reflecting a greater longevity by about 2 months. Although recruitment can be fairly continuous throughout the year, size-frequency analyses of D. variabilis in separate years at the same locality reveal substantial interannual differences in population dynamics