Improving Resolution In Dental Cementum Analyses Applied To Archaeological Contexts: The CemeNTAA Project

WILLIAM RENDU; LIONEL GOURICHON; HALA ALARASHI; EMILIE BLAISE; SANDRINE BONNARDIN; TIMOTHY G. BROMAGE; PAM J. CRABTRE; EMMANUEL DISCAMPS; VALÉRIE DUBOIS; ELODIE-LAURE JIMINEZ; STEPHAN NAJI; VANESSA PARMIGIANI; ERIC PUBERT; STUART R. STOCK; RANDALL WHITE

Londres

Congreso; European Society for the study of Human Evolution; 2015

In archaeology, seasonality is a key topic for the reconstruction and understanding of the subsistence systems and settlement patterns of past human communities. In prehistoric as well as in historical times, intra-annual variations and changes in environmental conditions, food resource availability, residential mobility, etc.., directly impacted social and economic activities. Such important issues surrounding the human behavior and the organization of social and economic activities closely linked to seasonality can be studied using the seasonal data derived from archaeological contexts. Among various methodological approaches, the analysis of incremental structures within the tooth cementum ? also known as cementochronology ? has been developed to tackle such questions. It relies on the study of the dynamic patterns and rhythmicity in the deposition rate of the dental cementum. In many mammalian species, including human, cementum growth follows predictable seasonal cycles with an alternation of fast and slow rate deposits during respectively growth and non-growth seasons. The outermost increment, forming at the time of death, is expected to give precise estimation of the season at death.While this method has been applied in zoology and archaeology for many years, several issues have been raised and need now to be investigated: ?Lack of reliable data about the timing of cementum growth for many species commonly found in archaeological sites and about variability between individuals or geographical populations;?Absence of standardized procedures of examination and interpretation of the cementum increments;?Partial destruction of the archaeological specimens by the most commonly applied technique of sample preparation (petrographic thin sections). CemeNTAA consortium proposes a three step program to challenge the application of cementochronological analyses to archaeological contexts.Firstly, through different interobserver blind tests, a common protocol has been constituted. It will allow a better reliability of the observations and to a minimization of the inter-observer discrepancies or errors.Secondly, a renew documentation of the biological phenomena has been made through the constitution of new comparative collections of modern specimens as well as archaeological sets gathering the main Pleistocene and Holocene European preys (Reindeer, Red Deer, Fallow Deer, Bison, Aurochs, etc.). It allows the identification of the intra-population variability of the cementogenesis phenomena. At term, it will be of help to systematically propose a standard deviation to all seasonal estimation. In the same time, these data progressively increase our open access database presenting analyses and pictures of teeth from different comparative collections. Finally, multi-scale approaches (optical, microtomography and X-ray fluorescence analysis) are conducted to increase our knowledge of the cementogenesis. Using some specific markers, the first results lead to the establishment of a 3D mapping of the cementum in order to minimize the sampling within a specified tooth and thus to produce a less destructive method.The application to archaeological material is conducted simultaneously. We investigate through the cementochronological lens how past human populations coped with seasonal constraints during two major phases of the human past: the transition from the Middle to Upper Paleolithic and the Neolithic revolution. These two periods are characterized by different sets of seasonal pressures. The end of the Middle Palaeolithic in Southwestern France is marked by major climatic fluctuation and the replacement of migratory taxa by sedentary ones, forcing Neanderthals to adapt their hunting strategies. During the second transition for the first time in the human history, the early farming communities had to deal with seasonal issues raised by the adoption of a food-producing economy.