The Emergence of Muge Mesolithic Shell Middens in Central Portugal and the 8200 cal yr BP Cold Event

ABSTRACT

The emergence of Portugal's Muge Mesolithic, with its characteristic shell middens and human burials, is widely seen as a response to the formation of a highly diverse terrestrial and aquatic ecotone in the Tagus basin by the Flandrian transgression. Recently, some have suggested that this was an adaptive response to the 8200 cal yr BP event. Using the available radiocarbon data for the shell middens, paleoclimatic data, and paleoceanographic data we present a new model for the appearance of the Muge Mesolithic shell middens and changes in settlement between the Boreal and Atlantic phases for central Portugal. Coastal ecosystems were altered due to diminution in upwelling and the occurrence of the 8.2 kyr cold event, with declining availability of marine resources, rapid sea level rise, and changes in coastal morphology. The result was that the previous coastal setting was no longer suitable for the hunter-gatherer-fishers causing a settlement shift to the new, large, and stable estuary of the Tagus Valley.

Keywords:

• coastal settlement
• Early Holocene
• upwelling
• Iberia

ACKNOWLEDGEMENTS

We thank Alice Newton, Delminda Moura, Jonathan Haws, Óscar Ferreira, and Fiona Petchey for help with the technical aspects of, respectively, the upwelling system, geomorphology of the Tagus Valley, revision of the paper, and radiocarbon dating. We are also indebted to the editors and anonymous reviewers for help in the review and revision of this paper. Naturally, all mistakes are ours alone. This paper is a result of the research project. The Last Hunter-gatherers in the Tagus Valley—The Muge Shellmiddens (PTDC/HAH/64185/2006) funded by Fundação para a Ciência e Tecnologia, Portugal.

Notes

¹Dates BP in Valente (2008) and Soares and Dias (2006) (secondary data sources); % marine diet from Martins et al. (2008). Calibration curves are IntCal04 (Reimer et al. 2004) and Marine04 (Hughen et al. 2004).

  ²Second date from a pair from the same shell, corresponding to the internal and intermediate fractions (the third fraction was removed and destroyed with acid to remove possible contaminants). The first date is shaded and no calibration was carried out.

  ³ΔR values from Soares and Dias (2006). If there is no specific ΔR value known for the site or nearby site then the value is the standard value of 380 ± 30.

  ⁴Estimated ΔR values based on proximity of space and time with the obtained values by Soares and Dias (2006).