Using Stable Isotopes and a Bayesian Mixing Model (FRUITS) to Investigate Diet at the Early Neolithic Site of Carding Mill Bay, Scotland

Jessica M Bownes,Gordon T Cook,Iona Murray,Philippa L Ascough,Clive Bonsall

doi:10.1017/rdc.2017.39

Abstract

AbstractWe present δ13C, δ15N, and δ34S measurements on archaeological human and animal bone collagen samples from a shell midden dating to the Neolithic ca. 4000–3500 cal BC, together with measurements on modern fish and shellfish. These data were used in conjunction with the Bayesian mixing model, Food Reconstruction Using Isotopic Transferred Signals (FRUITS), to reconstruct human diet at the site. We demonstrate the importance of using a geographically appropriate faunal baseline in stable isotope paleodietary studies, and suggest that Neolithic individuals at this site consumed up to ca. 21% of dietary protein from marine resources, despite stable isotope ratios that imply a wholly terrestrial diet. This marine resource consumption does not significantly shift the radiocarbon (14C) dates of these individuals, so although we must consider the use of marine resources at the site, the chronology that has previously been established is secure. The δ13C and δ15N measurements from the archaeological herbivore bone collagen indicate that it is unlikely they ate plants enriched with fertilisers such as manure or seaweed. The δ34S values reveal a sea-spray effect; therefore, in this instance, δ34S cannot be used as a dietary indicator but can be used to demonstrate the likely locality of the fauna.

Highlights

The Mesolithic-Neolithic transition marked a profound shift in socioeconomic patterns, which is represented in the archaeological record by stark changes in material culture and subsistence practices
The work we present here sought to better understand the dietary changes that occurred during the Mesolithic-Neolithic transition in western Scotland, using δ13C, δ15N, and δ34S isotope measurements on bone collagen from human and animal remains from Carding Mill Bay
This is noteworthy, since, even after correction of the ages, these individuals date to the first half of the Scottish Neolithic; do we demonstrate that the chronology of the site is reliable and secure, but we show that fish and shellfish in the diet can be firmly associated with the Neolithic

Summary

Introduction

The Mesolithic-Neolithic transition marked a profound shift in socioeconomic patterns, which is represented in the archaeological record by stark changes in material culture and subsistence practices. The nature and timing of the Mesolithic-Neolithic transition remains a much-debated topic in archaeology. Palaeogenetic research into the transition in the British Isles is less advanced and archaeological opinion is still divided over whether colonisation from mainland Europe (Sheridan 2010) or indigenous adoption (Thomas 2008) was the main driver of Neolithization. Regardless of the eventual outcome of the debate over the nature and timing of the transition in the British Isles, it is pertinent that we seek answers to more detailed questions about human lifestyle at this key juncture in prehistory. The extent of dietary change associated with the Mesolithic-Neolithic transition in Scotland is one such question that remains controversial. Stable isotope analysis for dietary reconstruction has been employed to investigate these changes (Richards and Mellars 1998), but is constrained by the scarcity of Mesolithic human remains from Scotland.

Methods

Results

Conclusion