Research Article: Quantifying spatial variability in shell midden formation in the Farasan Islands, Saudi Arabia

Date Published: June 12, 2019

Publisher: Public Library of Science

Author(s): Niklas Hausmann, Matthew Meredith-Williams, Katerina Douka, Robyn H. Inglis, Geoff Bailey, Clive Bonsall.

http://doi.org/10.1371/journal.pone.0217596

Abstract

During the past decade, over 3000 shell middens or shell matrix deposits have been discovered on the Farasan Islands in the southern Red Sea, dating to the period c. 7,360 to 4,700 years ago. Many of the sites are distributed along a palaeoshoreline which is now 2–3 m above present sea level. Others form clusters with some sites on the shoreline and others located inland over distances of c. 30 m to 1 km. We refer to these inland sites as ‘post-shore’ sites. Following Meehan, who observed a similar spatial separation in shell deposition in her ethnographic study of Anbarra shellgathering in the Northern Territory of Australia, we hypothesise that the shoreline sites are specialised sites for the processing or immediate consumption of shell food, and the post-shore sites are habitation sites used for a variety of activities. We test this proposition through a systematic analysis of 55 radiocarbon dates and measurement of shell quantities from the excavation of 15 shell matrix sites in a variety of locations including shoreline and post-shore sites. Our results demonstrate large differences in rates of shell accumulation between these two types of sites and selective removal of shoreline sites by changes in sea level. We also discuss the wider implications for understanding the differential preservation and visibility of shell-matrix deposits in coastal settings in other parts of the world extending back into the later Pleistocene in association with periods of lowersea level. Our results highlight the importance of taphonomic factors of post-depositional degradation and destruction, rates of shell accumulation, the influence on site location of factors other than shell food supply, and the relative distance of deposits from their nearest palaeoshorelines as key variables in the interpretation of shell quantities. Failure to take these variables into account when investigating shells and shell-matrix deposits in late Pleistocene and early Holocene contexts is likely to compromise interpretations of the role and significance of shell food in human evolutionary and socio-cultural development.

Partial Text

Globally, shell middens, that is sites in which discarded mollusc shells are the dominant physical constituent of the deposit, also known as shell-matrix deposits, are typical coastal sites [1–7]. They serve as important archives of past human life, as they contain not only abundant remains of mollusc shell but also provide a chemical and structural environment that protects other archaeological and biological remains [8–10]. Because of this, shell midden sites provide archaeological information on prehistoric and pre-contact hunter-fisher-gatherer and agricultural societies in many coastal landscapes of the world, as well as ecological information about their associated climate and environment [11–14]. Shell-matrix sites composed of freshwater mollusc-shells or terrestrial molluscs are also known in inland locations in many parts of the world[15,16], however in this paper we focus on coastal middens and marine molluscs in a mobile hunter-gatherer context. The large quantities of shells resulting from shell food consumption, their relative durability and resistance to decay, and their tendency to form substantial mounds of high archaeological visibility have all encouraged a long history and variety of studies devoted to such issues as chronology, site function, palaeodiet, palaeoeconomy, and the long-term history of coastal adaptations and their evolutionary consequences, with an extensive literature on the appropriateness and accuracy of quantitative measures such as the volume of shell-matrix deposits, numbers of shells collected, shell-to-meat-weight ratios, and comparisons with other food remains [4,17–23]. This is true both for mid to late Holocene periods, which are well known for the ubiquity of their shell matrix sites, as well as for early Holocene and late Pleistocene periods, where coastal evidence is much more elusive, as sea level change would have submerged most coastlines for much of this period [24–26].

The Farasan Islands are located in a fertile marine environment in the southern Red Sea between East Africa and the Arabian Peninsula, a crucial junction for population movements and cultural exchange between the two landmasses [56–59]. They comprise over 120 islands of varying size, the two largest being Farasan Kabir and Saqid (Fig 1).

 

Source:

http://doi.org/10.1371/journal.pone.0217596

 

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