The west-coast of Saudi Arabia is a desert landscape with temperatures ranging between 22°C and 38°C. There are no rivers or lakes and the maximum rainfall one can expect per month is only 22 mm. Data from environmental proxies indicate that these conditions have been the same for the last 7,000 years (Lézine 2014).
However, this did not keep people from living there. Vast amounts of coastal sites were found all over the southern coast of the Red Sea (Meredith-Williams et al. 2014). Most of the known sites are located on an archipelago called the Farasan Islands (www.disperse-project.org). Excavations and surveys in 2006-2009 found over 3,000 sites on the big islands alone (Bailey et al. 2007). The main part of the sites is made up of shell middens, this type of site can be found all over the world (Colonese et al. 2011, Estévez et al. 2001, Gutiérrez-Zugasti et al. 2011, Rabett et al. 2011), examples in the UK include shell mounds on the Isle of Portland (Mannino and Thomas 2001).
Shell middens are the leftovers from people collecting and processing molluscs and then depositing the remains on the beach. But many middens do not only contain shells. They also contain other food remains, burials, lithic tools, housing structures, etc.
It is the rigid structure of the shell as well as its chemical composition that works like a shelter for artefacts and bones. This also means that sometimes the only finds that are preserved can be found inside the middens, making them a prime location to look for intact material which later can be used for scientific analyses (e.g. residue analysis (Heron et al. 2007)).
The shells themselves can be used to ask questions about food preference and subsistence strategies. How many oysters did people eat? Did they prefer to eat fish or other mollusc species (Álvarez-Fernández 2001)? But also, was the local marine environment possibly unsuitable for some species? Can we see a change in marine environment that is reflected in a change of species throughout time (Carbotte et al. 2004)? These are all questions that can be looked into by analysing the animal remains and the taxonomic data.
For Farasan we try to answer other questions as well. For example we analyse the elemental and isotopic composition of the shell growth rings to reconstruct the temperature that the shells lived in. For this δ18O values from the shell carbonate (δ18OS) can be used in combination with the water composition (δ18OW) to calculate an estimated temperature using the equation below (Dettman et al. 1999).
SST (ºC) = 20.6 – 4.34 (δ18OS – (δ18OW – 0.27))
This can help us to understand what the temperatures were like in the past but also how dry or humid it was. This is especially interesting in desert landscapes like Saudi Arabia.
Furthermore, by sampling multiple growth rings in a line the temperature reconstruction can be used to find out about the seasonal change throughout the year. Goodwin et al. (2003) described the change in the seasonal curve for different scenarios.
However, the isotopic change is different for every shell species and different in every environment. The scenarios only illustrate what characteristics can be found in data.
The seasonal isotopic change in the shell carbonate can also indicate at what time of the year the mollusc was killed and when the people who made the shell midden ate it. Eerkens et al. (2013) used this technique to track people’s movement within the San Francisco Bay area. On Farasan we will be able to look if people moved to and from the islands at specific times of the year and if there has been a strong connection to the Arabian mainland. We could find that people stayed on the islands for the whole year to enjoy the rich marine wildlife.
About the Author:
Niklas Hausmann is a PhD Researcher within the Department of Archaeology at the University of York. His research is part of the DISPERSE Project, working on the Farasan Islands in the southern Red Sea. His research examines the isotopic composition of shells on the Farasan Islands, which feature more than 3000 shell middens, using the isotopic signature as an environmental proxy for sea surface temperatures (SST). Niklas hopes that the resulting understanding of seasonality can reveal subsistence strategies of local prehistoric populations, revealing gathering strategies and shellmound construction methods. Abundant shells within each layer of the middens provide a high density of samples, providing a high resolution dataset reflecting pre-desertification coastal exploitation in Saudi Arabia. Niklas undertook a BSc in Prehistoric and Historic Archaeology with Geosciences at Christian-Albrechts-Universität (CAU) Kiel, Germany, his dissertation focussed on the analysis of Kongemosian and Ertebølle lithic technology and faunal assemblages from Satrup LA 2. He then completed an MA in Mesolithic Studies at the University of York, focussing on spatial analysis of lithics from Duvensee 13. He is due to complete his PhD in September 2015.
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