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Understanding the onset and impact of Aquatic Resource Consumption in Human Evolution using novel Isotopic tracerS

Periodic Reporting for period 1 - ARCHEIS (Understanding the onset and impact of Aquatic Resource Consumption in Human Evolution using novel Isotopic tracerS)

Reporting period: 2019-03-01 to 2020-08-31

The onset of the systematic consumption of marine resources is thought to mark a turning point for the hominin lineage. To date, this onset cannot be traced, since classic isotope markers are not preserved beyond 50 - 100 ky. Aquatic food products are essential in human nutrition as the main source of polyunsaturated fatty acids in hunter-gatherer diets. The exploitation of marine resources is also thought to have reduced human mobility and enhanced social and technological complexification. Systematic aquatic food consumption could well have been a distinctive feature of Homo sapiens species among his fellow hominins, and has been linked to the astonishing leap in human intelligence and conscience. Yet, this hypothesis is challenged by the existence of mollusk and marine mammal bone remains at Neanderthal archeological sites.

The question of past hominin diets has its role in modern society as its documentation reveals the variability of human diets through times, when we, ourselves, might have to adapt our diets for a more sustainable society. However, the main outcome of this study is a better knowledge of the interaction between human evolution and subsistence strategies.

Recent work demonstrated the sensitivity of Zn isotope composition in bioapatite, the mineral part of bones and teeth, to dietary Zn. By combining classic (C and C/N isotope analyses) and innovative techniques (compound specific C/N and bulk Zn isotope analyses); the ARCHEIS project aims at developing an isotopic tool capable to establish the onset of fish consumption relative to that of shellfish and link the introduction of marine food in hominin diets to their cultural and biological evolution. It will investigate the dependence of d66Zn on trophic level and marine food consumption, by establishing the isotope fractionation mechanisms during intestinal absorption and studying populations consuming aquatic food from different trophic levels: shellfish (low trophic level), fish (intermediate trophic levels) and marine mammals (high trophic levels). The project will also address unsolved questions surrounding the disappearance of pre-Columbian shell mound societies of the Brazilian coast around 2000 BP and the debate on fish consumption of Paleolithic, Mesolithic and Neolithic modern humans.
WP 1: Calibration of the relationships between aquatic food consumption and bodily Zn stable isotopic compositions.

We made excellent progress on the experimental part of the WP1 and the first publication is in preparation.

Work Package 2: Exploration of Zn isotope signatures in teeth of archeological populations with known aquatic food consumption.

Because of the COVID-19, this part of the project has been delayed by the postponed arrival of the hired PhD student and postdoc. However, the fauna and human material for this part of the project has been selected (shell midden sites) and a PhD student is starting working on the Zn isotope analyses. We already published the data for the inland population of Lapa do Santo studied for comparison (Jaouen, Trost et al. 2020, Plos One). We discovered that Zn isotopes are a tracer of the weaning age in archeological populations. Looking for two additional populations with known aquatic food consumption, we obtained unexpected results of historical interest, that have been submitted for publication.

Work Package 3: Development of quasi-non destructive sampling method for Zn isotope analysis

We are actively working on this aspect of the project that already gives promising results

Work Package 4: Tracking the rise and fall of aquatic food exploitation in prehistoric times

We finished the isotope analyses of our project tracking aquatic food consumption in the Breton Neolithic. We are actively working on projects involving Paleolithic hominins. We documented the preservation of Zn isotopes in a tropical Pleistocene foodweb for which organic matter was not preserved (Bourgon et al., PNAS, 2020) which shows how promising this tracer is to track ancient diets.
The ARCHEIS project already documented the possibility to track the age of weaning and diet using Zn isotopes, in the absence of collagen preservation.

Until the end of the project, we aim at documenting how they can be used to track specific types of seafood consumption using a minimal amount of archeological material