Thursday, 19 February 2015

Prehistoric eating habits... by Niklas Hausmann

Niklas Hausmann is working on shells from archaeological sites in Saudi Arabia to reconstruct prehistoric eating habits and environmental change. As part of his PhD he is working within the Stable Isotope Facility at the BGS to analyse his shells for their geochemistry and to get away from the boiling heat of the Red Sea…

In the last 3 years, as part of my PhD in the DISPERSE Project at the University of York, I have worked extensively on the Farasan Islands (Google Maps link) in the southern Red Sea, which definitely has its upsides. You are surrounded by crystal clear water and, more importantly, you are able to eat extremely tasty fish every night.

Living specimen of Conomurex fasciatus.
Sichel-shaped operculum (a kind of trap door hatch)
can be used as a pick to eat the animal after it is cooked.
My supervisor Professor Geoff Bailey surveyed Farasan in 2003 and found a massive amount of shells heaped up by past inhabitants of the islands dating around the mid-Holocene (5,000 years ago). It was probably the archaeology that drove him to apply for funding for an excavation, but I want to believe that it also was the food. Either way, together with Geoffrey King from the Institut de Physique du Globe de Paris (IPGP), he came up with the DISPERSE research project which looks at human dispersal across the Red Sea during prehistory. The Farasan Islands are an important part of this dispersal as they are the only place where we find well preserved sites on the Arabian coastline, and they can be used as a reference for marine exploitation for the wider area of the southern Red Sea.

Shell mound at Janaba Bay. Cars to indicate scale
While Geoff started above-water and underwater excavations in 2006, 2008, and 2009, I only started my PhD on the project in 2012. My research is especially focused on the shell mounds themselves. I look at how the shells accumulated (were eaten by people) and what kind of environmental information I could get out of the shells themselves. It can’t have always been this hot!

Luckily, there were not many shell species that I needed to analyse, because 95% of the shell mounds consisted of the species Conomurex fasciatus (or Strombus fasciatus, the common name is the lined conch). Unfortunately, there is not much published on this species,  however, we know that the shells are generally between 2 and 5 cm, they are found almost exclusively in the Red Sea and the Persian Gulf, and are very pretty!

Artisanal fishers invited the team on a cruise
(Photo © C. Beresford)
It is assumed that the conch prefer shallow water in sandy and calm areas. But when we went out to look for it, it was almost never to be found in those areas. I spent many hours diving at all kinds of beaches (and enjoying myself despite the occasional stingray encounter). The result was a red hot sunburn and only two areas where I found the shellfish. Both places experienced heavy wave action and instead of sand I only found rough coral bedrock. I am not sure what the molluscs prefer in the end, but I liked the smooth beaches better.

Typical amount from 30 min of fishing (Photo © C. Beresford)
To find out about depositional patterns and the prehistoric environment, I am using geochemistry. Oxygen ratios in the shell can tell us about temperature and the saltiness of the water. I would have to figure out how both factors interact or if one of them is dominant.

For once, the incredibly hot conditions and aridity of the desert landscape had an advantage! If there is no rain, and there are no rivers or generally no freshwater bodies whatsoever (so the shells live in normal saltiness sea water), then they cannot mess up my geochemistry. Good news for me! It did rain once while I was on the Farasan Islands, it was over soon and flowed off the island within minutes.

Me, visually analysing erosional processes after
a very rare rain shower at Janaba Bay (Photo © R. Inglis)
After we collected modern shells from different seasons and compared their geochemistry to the temperature throughout the year, we had a baseline to show how we could reconstruct past sea water temperatures from the archaeological shells. I am now sampling the archaeological shells to find out at what time of the year people were gathering shellfish and how hot the ocean was. Combined with the archaeological context this can tell me a lot about their food preferences, how much they collected at a time, and if they used the sites continuously or only came a few times.

In the bigger perspective, we can apply these results to the rest of the southern Red Sea and have an idea of how rich the marine wildlife was and how important it was as food source in comparison to the desert landscape of Arabia.

Niklas

Niklas Hausmann is a PhD student in the Department of Archaeology at the University of York. He is supervised at the BGS by Melanie Leng in the Stable Isotope Facility.

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