Broomcorn millet (Panicum miliaceum) is considered as staple food for Europeans during prehistory. As a matter of fact, the Bronze Age was called Millet Golden Age by Marinval (1995). This cereal is distinct from those domesticated in the Fertile Crescent since its domestication was probably realised in Central Asia or China, and then its cultivation diffused towards the west thanks to population migrations or trades. The exact timing and routes of this diffusion, although documented by a large number of archaeological findings, remain to be precised. This would provide a more detailed picture of trading routes and migration pathways and pace of exchanges, with eventual relationships to climate changes.We have analysed miliacin, a molecular biomarker of millet (Jacob et al., 2008), in sediments from lakes Ledro (Utaly), Le Bourget, Paladru, Aiguebelette and La Thuile (France) in order to precise the timing of millet diffusion during the Neolithic and Bronze Age. The first occurrence of miliacin in Ledro is dated back to 2400 BC. In Le Bourget, Paladru, Aiguebelette and La Thuile, the date of first miliacin appearance is remarkably synchronous around 1500 BC. Miliacin was also detected at low levels in all older sediments in La Thuile. This could result either from laboratory contamination or from the presence of an alternative miliacin source in the catchment. Indeed miliacin is found in low amounts in several other Poaceae (Bossard et al., 2013). In Aiguebelette, a single sample dated back to the Neolithic (~2300 BC) shows significant miliacin concentrations. Because this date is close to that found in Ledro, it could attest to an early attempt of millet cultivation, but would imply a rapid diffusion from the East.Finally, the evolution of millet concentration in sediments of Le Bourget, La Thuile and Aiguebelette allows us making several assumptions on the development of alpine populations during the Bronze Age, Iron Age and Antiquity in the region, potentially linked to climate changes that affected the region at those times. ReferencesJacob et al., 2008. Millet cultivation history in the French Alps as evidenced by a sedimentary molecule. Journal of Archaeological Science 35, 814–820.Marinval, 1995. Données carpologiques françaises sur les millets (Panicum miliaceum L. et Setaria italica L. Beauc.) de la Protohistoire au Moyen Age. In Hörrandner, E., editor, Millet. Actes du Congrès d'Aizenay (1990). Peter Lang, 31-61.Bossard et al., 2013. Distribution of miliacin (olean-18-en-3β-ol methyl ether) in broomcorn millet (Panicum miliaceum), and other reputed potential sources. Consequences on the use of sedimentary miliacin as a tracer of millet. Organic Geochemistry 63, 48-55.