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Introduction
Introduction
During the 6th millennium BC a series of events occurred along the North Western Mediterranean coastlines that transformed society and had far-reaching effects on human demography, health, social organisation and ideology: the arrival of farming. The process is believed to be the result of colonisation, as early farmers migrated westwards following a coastal route from the Aegean, bringing with them pottery, ground stone tools and domesticated plants and animals, marking the start of the Neolithic period. Whilst this forms a clear archaeological horizon known in central and western Mediterranean as the Impresso-Cardial Complex (ICC), the degree to which these groups were culturally influenced and genetically admixed with indigenous hunter-gatherers is still unresolved. This question mirrors a long-standing debate regarding the origins of farming that has occupied prehistorians and archaeologists for over a century but is now beginning to be addressed through the application of new biomolecular analysis of skeletal remains, such as DNA and stable isotope analysis.
The analysis of ancient genomes from human remains in the Mediterranean region would seem to be the most logical approach to resolve this issue but such analysis has so far been limited to a small number of samples from Northern Spain. These data show that the Early Neolithic individuals have very different ancestry to Late Mesolithic hunter- gatherers, supporting the idea of the rapid maritime colonisation by exogenous farming groups. Intriguingly it seems that these Neolithic farmers subsequently became significantly admixed with local hunter-gatherers and within 1000 years, indigenous hunter-gatherer ancestry accounts for ca. 25% of genomes analysed. The genetic data however, provide no clue concerning the tempo for increasing hunter-gatherer/farmer admixture during this period and it is unclear whether this was ‘on arrival’ or sometime later in the Neolithic. Ancient DNA is also unable to resolve the underlying processes regarding the transition, notably the degree to which these incoming groups relied on food production (i.e. agriculture and pastoralism) as opposed to wild resources (gathered, hunted and fished foods).
To address this last question an alternative scientific approach has been to directly determine diet through stable isotope analysis of skeletal remains. Essentially, diets of ancient individuals can be estimated by measuring stable isotopes of carbon (δ13C) and nitrogen (δ15N) present in bone protein (collagen) extracted from their skeletal tissues and comparing these with measurements from potential foodstuffs. For coastal populations this approach is particularly appealing since marine organisms generally have very distinctive isotopic signatures compared to terrestrial resources, allowing generic discriminations.
The rationale behind this approach is to demonstrate either
- the continuity in the use of wild foods, including marine resources, indicating the active involvement of indigenous Mesolithic foragers in the spread of farming and/or the acculturation of incoming ‘farmers’ who also relied on hunting/gathering and fishing (Scenario 1); or
- a complete reliance on terrestrial resources, such as domesticated herbivores and cereals, which would instead point to the ‘revolutionary’ shift in diet, as has been suggested for Northern Europe. This is akin to the accumulation of local hunter-gatherers who effectively became farmers (Scenario 2).
State-of-the-art
State-of-the-art
Stable isotope studies so far using the analysis of bulk collagen from bone have shown that ICC and later Neolithic diets were uniformly based on terrestrial foods despite their coastal location and differ from Late Mesolithic coastal forager/fishers. Whilst this observation is more consistent with Scenario 2, crucially the approach lacks the necessary resolution to quantify dietary components or detect low but significant marine consumption (e.g. <20%) which would validate Scenario 1. More broadly, it is increasingly apparent that stable isotope of bulk collagen has fundamental limitations for paleodietary reconstructions, as collagen may be synthesised from different dietary macronutrients, specifically protein, carbohydrate and lipids.
Then, a mixed diet consisting of macronutrients derived from different amounts of marine and terrestrial foods is not easily decipherable from bulk collagen stable isotope values. Second, the use of only two isotopes, δ13C and δ15N, limits the dimensions for discriminating different foods and, more importantly, mixtures of these. Third, and most damning, the δ13C differences between food and the consumer’s bone collagen varies depending on diet, leading to erroneous representations of marine and terrestrial resource consumptions in the past.
Objectives
Objectives
The overarching aims of the project are to:
- produce population level, in depth, uniquely detailed dietary reconstructions of Neolithic humans in the western Mediterranean (Spain, France and Italy) that will serve as guidelines for future dietary reconstructions;
- address fundamental questions related to the early use of marine resources in this region in order to validate the hypotheses outlined above.
To achieve these aims the research objectives (ROs) are:
- RO1: to develop and optimize protocols for the measurement of single compounds in bone by Gas Chromatography- combustion Isotope Ratio Mass Spectrometry (GC-c-IRMS).
- RO2: to establish AA isotopic baselines for the Mediterranean regions in study.
- RO3: to generate AA isotope data from selected Mesolithic and Neolithic human collagen samples from the region.
- RO4: to provide probabilistic determinations of the relative proportions of different foods to diet.
- RO5: to examine patterns and correspondences with the corpus of archaeological data available and to disseminate the results to broad audiences.
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