Prehistoric cooking versus accurate palaeotemperature records in shell\xa0midden constituents

Peter Müller,Robert Vernet,Hildegard Westphal,Peter K Swart,Philip T Staudigel,Jean-Paul Barusseau,Sean T Murray

doi:10.1038/s41598-017-03715-8

Abstract

The reconstruction of pre-depositional cooking treatments used by prehistoric coastal populations for processing aquatic faunal resources is often difficult in archaeological shell midden assemblages. Besides limiting our knowledge of various social, cultural, economic and technological aspects of shell midden formation, unknown pre-depositional cooking techniques can also introduce large errors in palaeoclimate reconstructions as they can considerably alter the geochemical proxy signatures in calcareous skeletal structures such as bivalve shells or fish otoliths. Based on experimental and archaeological data, we show that carbonate clumped-isotope thermometry can be used to detect and reconstruct prehistoric processing methods in skeletal aragonite from archaeological shell midden assemblages. Given the temperature-dependent re-equilibration of clumped isotopes in aragonitic carbonates, this allows specific processing, cooking or trash dispersal strategies such as boiling, roasting, or burning to be differentiated. Besides permitting the detailed reconstruction of cultural or technological aspects of shell midden formation, this also allows erroneous palaeoclimate reconstructions to be avoided as all aragonitic shells subjected to pre-historic cooking methods show a clear alteration of their initial oxygen isotopic composition.

Highlights

Many prehistoric coastal populations have exploited the faunal resources of adjacent aquatic environments[1, 2]
As subsistence was the primary reason for exploiting aquatic faunal resources for many prehistoric cultures, most shell midden constituents were most-likely subjected to certain processing or cooking techniques prior to deposition[4], In particular molluscs, where the comparably small amount of edible flesh is protected by tightly closed valves or an operculum require sophisticated processing strategies in order to efficiently extract the small edible portion[4, 6]
While usually unknown processing methods limit our understanding of shell midden formation, processing or cooking methods can alter the geochemical proxy records of calcareous skeletal remains, potentially

Summary

Introduction

Many prehistoric coastal populations have exploited the faunal resources of adjacent aquatic environments[1, 2]. As subsistence was the primary reason for exploiting aquatic faunal resources for many prehistoric cultures, most shell midden constituents were most-likely subjected to certain processing or cooking techniques prior to deposition[4], In particular molluscs, where the comparably small amount of edible flesh is protected by tightly closed valves or an operculum require sophisticated processing strategies in order to efficiently extract the small edible portion[4, 6]. Evidence for certain processing or cooking techniques such as pottery and tool fragments or blackened/burned stones are often sparse in shell midden deposits or allow a variety of potential interpretations regarding specific cooking or processing strategies. This is true at transitory preparation sites near fishing or shellfish gathering grounds rather than close to prehistoric settlements. Clumped-isotope thermometry might represent an ideal tool to detect pre-depositional heating of aragonitic shell midden constituents and may allow certain processing or cooking practices to be differentiated

Methods

Results

Conclusion