The place of millet in food globalization during Late Prehistory as evidenced by new bioarchaeological data from the Caucasus

Two millets, Panicum miliaceum and Setaria italica, were domesticated in northern China, around 6000 BC. Although its oldest evidence is in Asia, possible independent domestication of these species in the Caucasus has often been proposed. To verify this hypothesis, a multiproxy research program (Orimil) was designed to detect the first evidence of millet in this region. It included a critical review of the occurrence of archaeological millet in the Caucasus, up to Antiquity; isotopic analyses of human and animal bones and charred grains; and radiocarbon dating of millet grains from archaeological contexts dated from the Early Bronze Age (3500–2500 BC) to the 1st Century BC. The results show that these two cereals were cultivated during the Middle Bronze Age (MBA), around 2000–1800 BC, especially Setaria italica which is the most ancient millet found in Georgia. Isotopic analyses also show a significant enrichment in 13C in human and animal tissues, indicating an increasing C4 plants consumption at the same period. More broadly, our results assert that millet was not present in the Caucasus in the Neolithic period. Its arrival in the region, based on existing data in Eurasia, was from the south, without excluding a possible local domestication of Setaria italica

Etude archéobotanique et isotopique du site de Chobareti (IV-IIIe millénaire, Transcaucasie). Premiers témoignages d'une céréaliculture de haute montagne à l'Age du Bronze ancien,

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. Modification des pratiques alimentaires au cours de l'âge du Bronze dans le Sud Caucase : Mise en évidence de la consommation de millet par une approche multi-isotopique.

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Comportements alimentaires humains et exploitation des plantes dans le Sud Caucase au Bronze ancien : approches anthropologique, isotopique et archéobotanique du site de Chobareti (1615 m, Géorgie).

International audienceComportements alimentaires humains et exploitation des plantes dans le Sud Caucase au Bronze ancien : approches anthropologique, isotopique et archéobotanique du site de Chobareti (1615 m, Géorgie)

Comportements alimentaires humains et exploitation des plantes dans le Sud Caucase au Bronze ancien : approches anthropologique, isotopique et archéobotanique du site de Chobareti (1615 m, Géorgie).

International audienceComportements alimentaires humains et exploitation des plantes dans le Sud Caucase au Bronze ancien : approches anthropologique, isotopique et archéobotanique du site de Chobareti (1615 m, Géorgie)

Topographic instability of flow in a rotating fluid

Here are presented the results of experimental and theoretical studies on a stability of zonal geostrophic flows in the rotating layer of the shallow water. In the experiments, a special apparatus by Abastumani Astrophysical Observatory Georgian Academy of Science was used. This apparatus represents a paraboloid of rotation, which can be set in a regulable rotation around the vertical axis. Maximal diameter of the paraboloid is 1.2 m, radius of curvature in the pole is 0.698 m. In the paraboloid, water spreads on walls as a layer uniform on height under the period of rotation 1.677 s. Against a background of the rotating fluid, the zonal flows are formed by the source-sink system. It consists of two concentric circular perforations on the paraboloid bottom (width is 0.3 cm, radiuses are 8.4 and 57.3 cm, respectively); water can be pumped through them with various velocities and in all directions. It has been established that under constant vertical depth of the rotating fluid the zonal flows are stable. There are given the measurements of the radial profiles for the water level and velocity in the stationary regime. It has been found that zonal flows may lose stability under the presence of the radial gradient of full depth formed by a change of angular velocity of paraboloid rotation. An instability origin results in the loss of flow axial symmetry and in the appearance of self-excited oscillations in the zonal flow. At the given angular velocity of rotation, instability is observed only in the definite range of intensities of the source-sink system. The theoretical estimations are performed in the framework of the equations of the shallow water theory, including the terms describing the bottom friction. It has been shown that the instability of zonal flows found experimentally has a topographical nature and is related with non-monotone dependence of the potential vorticity on radius